Author Topic: EEVblog #1030 - $20 DIY Bench Power Supply!  (Read 23975 times)

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Offline EEVblog

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EEVblog #1030 - $20 DIY Bench Power Supply!
« on: October 06, 2017, 07:57:22 am »
Dave looks at the spectacularly cheap $20 DPS series CC/CV modules from RD Tech.
How to make a 30V 3A bench power supply with 1mA resolution constant current limiting and multi function display using junk bin parts.
The DPS3003 30V 3A module in particular.

RDtech Youtube channel: http://www.youtube.com/channel/UCy73jJ5-ZqhPzT7wJ6KTIaw

Aliexpress Store: https://rdtech.aliexpress.com/store/923042


 
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Offline cdev

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #1 on: October 06, 2017, 08:21:32 am »
In one of the threads on these modules (here) around nine months to a year ago, I think the OP had figured out how to make the modules externally programmable.

Anyway, at some point the OP of that thread discoverd some glitch in the device which suddenly caused the voltage to become uncontrolled, and I think caused some kind of problem. I don't think this was in the standard use case, so it likely does not matter to viewers just looking for a power supply.

Also, this was a while ago so its entirely likely that whatever the glitch was the manufacturer may have fixed it.

I will try to find the exact link. This was when I was looking for a good power supply so I may have even bookmarked it.

So, if this glitch was fixed, these supplies may also be a good base for a project to build a programmable CV/CC supply.
« Last Edit: October 06, 2017, 08:39:56 am by cdev »
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Offline cezar

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #2 on: October 06, 2017, 09:00:24 am »
Those are being made by RD TECH. They also have their own YT channel

http://www.youtube.com/channel/UCy73jJ5-ZqhPzT7wJ6KTIaw/videos
 

Offline ManuelMcLure

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #3 on: October 06, 2017, 09:20:44 am »
I already have a bench top supply based on their DPH3205 buck-boost module. The power source is a Cosel 12V/13A switcher.
 
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Offline jamiec

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #4 on: October 06, 2017, 09:36:48 am »
I made one of these myself a couple of weeks ago and absolutely love it.
Would recommend to anyone, wanting a small PSU.

Here is a photo of my build:
« Last Edit: October 06, 2017, 09:38:25 am by jamiec »
 
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Online jaromir

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #5 on: October 06, 2017, 09:40:03 am »
That overshoot when relased from CC into resistor to CV with no load at 10V (last test) was only slight - perhaps it's because the module can't deliver more than 11something volts.
I wonder what the overshoot looks like when set to 5V, for example - whether it jumps to maximal input voltage too.
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Offline ez24

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #7 on: October 06, 2017, 10:55:42 am »
This Aliexpress seller (RD) has a chart of the specs and links for different models.  Scroll down to see the chart. 


https://www.aliexpress.com/item/R/32762131242.html

Edit: corrected link
« Last Edit: October 09, 2017, 10:41:48 am by ez24 »
YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 
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Offline cdev

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #8 on: October 06, 2017, 11:02:26 am »
Perfect thing for me to do with my 12v power supply from that era.. Which looks a lot like yours, boffin

That is, if I can figure out how to open its damn box!
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Offline Rabid Badger

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #9 on: October 06, 2017, 12:04:48 pm »
I built my bench PSU around the DPS3012.  I got a 36V 10A open frame power supply for $12 on eBay and put it in an old salvaged housing with a couple fans out of an old server.  Total out of pocket was $37 and it has handled some pretty stout sustained loads.

 
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Offline ziggyfish

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #10 on: October 06, 2017, 12:36:42 pm »
With the experience of the EEVBlog community, why isn't there an open hardware solution with a version of this?

The software side would be pretty straightforward (could do it with my eyes closed).
 

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Offline nixfu

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #12 on: October 06, 2017, 01:03:02 pm »
So are these step down only?  So if I want 20v I will need to input 25v or so?
 

Offline Rabid Badger

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #13 on: October 06, 2017, 01:32:14 pm »
There is a buck-boost version. Search for DPH3205.
 

Offline crazyguy

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #14 on: October 06, 2017, 01:44:08 pm »
So are these step down only?  So if I want 20v I will need to input 25v or so?

read the comparison chart posted in #7
 

Offline n3vti

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #15 on: October 06, 2017, 02:06:29 pm »
I love these!

So, I could in theory, make it into a mains plug in by building an unregulated power supply to supply the requirement for these modules? I think I have the parts to make a 36 volt (heavily filtered) DC at about 2-3 Amps.
 

Offline ziggyfish

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #16 on: October 06, 2017, 04:00:38 pm »
It is there already.

http://www.eevblog.com/forum/projects/diy-programmable-dual-channel-bench-psu-0-50v3a/

from their Crowd Funding page:

Quote
Next Manufacturing Run

As some of you have noticed, we’ve stopped taking new orders for the EEZ H24005. Because we intentionally didn’t include a large margin in our pricing, the cost of the current manufacturing run is essentially the price paid for each unit and there essentially won’t be any left over to sell outside of those already purchased. Parts have already been ordered and deposits already paid to our manufacturers, so we can no longer accommdate new orders in the current batch. However, we’ve been discussing making a second batch, so please subscribe to project updates if you’d like to be informed if/when a next batch becomes available.

I wonder when or if they are making more.
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #17 on: October 06, 2017, 05:16:33 pm »
There are new communication versions. You can control it via opto-isolated USB.
I have bought 4 of these modules:
https://www.aliexpress.com/item/RD-DPS5005-Communication-Function-Constant-Voltage-current-Step-down-Power-Supply-module-buck-Voltage-converter-LCD/1000004290003.html

IMHO this is the best bang for the buck version. The largest current with the compact design. Next model got a large external PCB.

This is the firs unit I built. It got a internal battery pack (75.8Wh, 11.4V, protection PCB with balancing). I can power it via a Dell laptop PSU or the internal battery pack. Size is only 10x10x5cm.

 
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Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #18 on: October 06, 2017, 05:22:39 pm »
The biggest flaw with these modules is the low side current measurement. You have to be careful if using these in parallel and /or using a non-floating DC PSU for power input. The return current may go the wrong path and skew the modules current measurement.

The ripple was surprisingly low in the DPS5005 module. This is measured with 12V input and 5v 5A output.
 

Offline sasa

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #19 on: October 06, 2017, 05:28:47 pm »
What kind of LCD is used?

I'm aware small OLEDs are extremely cheap on alibaba or similar sites, however this also may be some cheap TFT color LCD.
The 30+ years professional desktop software designer and software engineer
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #20 on: October 06, 2017, 05:29:16 pm »
Alternative firmware with simplified GUI and WLAN module support:
https://johan.kanflo.com/category/dps5005/
 
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Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #21 on: October 06, 2017, 05:31:48 pm »
What kind of LCD is used?

I'm aware small OLEDs are extremely cheap on alibaba or similar sites, however this also may be some cheap TFT color LCD.

The srceen is LCD not OLED.
 

Offline Red Squirrel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #22 on: October 06, 2017, 06:33:37 pm »
I'd be curious to see a test at it's rated current output.  >:D

These look pretty nifty though, might get one or two.  I need to build myself a variable bench supply anyway, still using an old ATX power supply with it's fixed voltage rails.

 

Offline Rolo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #23 on: October 06, 2017, 06:43:02 pm »
Going to build one, as second PSU next to my trusty Delta Elekronika. What do you think, will noise/ripple figures be better if the module is powered by a classic transformer , bridge rectifier and big cap? Or is it not worth the weight and size increase of the unit?

« Last Edit: October 06, 2017, 06:44:41 pm by Rolo »
 

Offline HKJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #24 on: October 06, 2017, 06:46:38 pm »
I have tested two of them with a lot of different input and output voltages:

http://lygte-info.dk/review/Power%20DPH3205%20UK.html
http://lygte-info.dk/review/Power%20DPS5015%20UK.html

 
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Offline CJay

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #25 on: October 06, 2017, 07:28:03 pm »
These look ideal for using some of the random transformers I've harvested over the years, seems I may not need to weigh them in for copper scrap.

Now all I have to do is work out some way to calculate or guesstimate the current capability of the transformers.   :-DD
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Offline fvdpol

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #26 on: October 06, 2017, 07:51:25 pm »
Thanks for showing these neat devices from RD Tech.  :-+ Would really love to see some more details on the performance and reliability of these devices, so maybe that could give an interesting (popular?) follow-up video.

Looking at the minuscule heatsinks I wonder what the safe operating range (voltage vs current) would be? Unless extremely efficient I'd expect the U/I curve would be significantly limited due to maximum power draw.  How would these behave versus different input voltages?

Reliability is something that worries me somewhat, as this is clearly build for a low manufacturing cost. A review/analysis on the design with potential failure points/modes would be interesting to see. The PSU dropping out, no current would be an OK failure mode, but I'd rather not see the full input voltage being dumped on the output.
 

Offline tuo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #27 on: October 06, 2017, 10:22:36 pm »
I would like to see a follow-up video about these modules. The questions could be what to use to provide the input voltage, especially when you'd like to  have more than 24V where most of the laptop power bricks seem to be limited, so a transformer or an SMPS, how to estimate how big these should be, getting everything in a one enclosure etc.

Very interesting modules indeed and a very interesting video as well.
 

Offline crx991

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #28 on: October 06, 2017, 11:47:01 pm »
Sorry for the dumb question, but i need a bench power supply for my hobbist projects ...
Wich is better? a unit like this (maybe an DPH3205) or something like tenma 72-10480?
I know the price difference is high, but i need something affordable, for example i've read about the voltage spikes for the tenma, something that is absent in this cheap units ...
I'm sorry if the question is really strupid, but I'm rookie :)
 

Offline DrMag

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #29 on: October 07, 2017, 02:13:00 am »
There are no dumb questions, only dumb questioners -- those who ask and refuse to hear the answer.

Any power supply at this price-point is going to have some compromises, and voltage spikes are certainly one of them. How severe that is depends on how you're using it, of course. Adding filtering on the output can help mitigate that.

One real advantage the Tenma will have in your case is that it will just plug into your wall and work. The units this thread is discussing require a power supply of their own to work--and which one you use will have a large impact on what the supply can do. If, for example, you use a wall supply that puts out 5 V and 1 A, you are limited to (roughly) 5 V and 1 A. You won't get 20 V 3 A no matter what you do, unless you have a power supply for your power supply that can handle it.

So be aware of that; these little modules are slick, and seem to be pretty well made. But to use them safely, you'll also need a good wall supply (which will cost as much as the module), and a decent case (which if you buy from RD Tech will again cost about as much as the module).

An equivalent to the Tenma you've listed using these modules would require:
RD DPS3003 (18.03 GBP)
RD DPS Supply Housing (17.60 GBP)
Wall Power Supply something like this (26.80 GBP)

With those choices, you're looking at roughly the same price between your two options (which really shouldn't come as a surprise). For a beginner, if the choice is between these two I would recommend the Tenma--fewer parts, and ultimately cheaper in the long run. The real advantage to these little modules is how easily they can be incorporated into other projects--they're compact and work pretty well.

That, of course, can be completely off if your goal is to learn to build things yourself, in which case a housing and a reasonable ac/dc converter can be made for quite a bit less (though likely not enough less to make this the cheaper option by much). Building a power supply is often considered a really good beginning project, and there are lots of resources out there. In this case, it would be simplified by not having to make it a variable supply--it only needs to be designed for >30 V fixed with enough capacity to handle more than 3 A of current. Then you would use the RD DPS module to provide your variable voltage and current outputs. Not a bad little project! Just be aware that if minimizing expense is critical, using a module like these will invariably incur expenses for other parts and could easily make it the more expensive route in the end.
« Last Edit: October 07, 2017, 02:15:45 am by DrMag »
 

Offline crx991

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #30 on: October 07, 2017, 02:58:05 am »
Thanks for the reply @DrMag,

For the DPS i've already have a power supply which can supply the required power, also for the case no problem, i love build by my self things  :-/O

About the tenma, for example, i've read it's a "good" power supply, but for the price, imho, has severe flaws, like the possibility to pick a bugged model (it's a clone of the infamous Korad for who knows the story behind this supply) and suffers from high spikes which i've read, even here, that can easly kill a sensible device... :horse:
Now (at right moment), dave's pushes out this rewiev and my alternatives magically appears :P
 

Offline CabanzoJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #31 on: October 07, 2017, 03:21:54 am »
Can I get two of these, wire them in series and get dual output (positive and negative)??
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #32 on: October 07, 2017, 03:31:45 am »
Can I get two of these, wire them in series and get dual output (positive and negative)??
Yes if you power them with two separate floating DC supplies.
 

Offline HKJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #33 on: October 07, 2017, 03:47:47 am »
Can I get two of these, wire them in series and get dual output (positive and negative)??

When doing that it is a very good idea to put a beefy diode across each set of output terminals (in reverse direction, of course) or a short may damage the power supply.
 

Offline HKJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #34 on: October 07, 2017, 04:25:49 am »
Now I got around to see David talk about it and how he doubt it can have 90% efficiency. The one I tested was much better than 90%and even at 14A it did not get that hot:
 
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Offline Fungus

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #35 on: October 07, 2017, 04:41:50 am »
Sorry for the dumb question, but i need a bench power supply for my hobbist projects ...
Wich is better? a unit like this (maybe an DPH3205) or something like tenma 72-10480?
I know the price difference is high, but i need something affordable, for example i've read about the voltage spikes for the tenma, something that is absent in this cheap units ...
I'm sorry if the question is really strupid, but I'm rookie :)

If you don't know the answer to that then get the cheap one.

nb. The main use for a bench supply usually isn't the variable voltage, it's the current limiting. Limiting the current to {2*$expected} can save many a project from going up in flames.
« Last Edit: October 07, 2017, 04:53:14 am by Fungus »
 

Offline DrMag

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #36 on: October 07, 2017, 04:49:15 am »
@HKJ: Sounds impressive! Which model did you test? At what output settings? I can see it being quite efficient at 5V/1A, but how about 30V/3A? (By which I mean the spec'd limits of the supply; the one Dave was showing was rated for 30V/3A. Was your 14A test at the limits of the supply?)

NVM; finally took a look at the test results you posted earlier. Nice work!  :-+
« Last Edit: October 07, 2017, 04:59:09 am by DrMag »
 

Offline HKJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #37 on: October 07, 2017, 05:14:53 am »
@HKJ: Sounds impressive! Which model did you test? At what output settings? I can see it being quite efficient at 5V/1A, but how about 30V/3A? (By which I mean the spec'd limits of the supply; the one Dave was showing was rated for 30V/3A. Was your 14A test at the limits of the supply?)

NVM; finally took a look at the test results you posted earlier. Nice work!  :-+

As you can see it was the highest power buck model and the buck/boost model and I did test them at a lot of voltage/current combinations, even with my automatic testing it took more than a day.
During test I could feel the heat, testing at about 700 watt will heat my small lab. Most of the heat from my electronic load (3x300W), some from the power supply (A 1.2kW TTi) and a little bit from the module.
I did also run a smaller module (30V 5A), but I did never get around to write a review about it, now it is probably too late (it was nearly a year ago).
 

Online retrolefty

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #38 on: October 07, 2017, 06:11:49 am »
Does anyone know how to utilize the M functions. Appears you can save specific V/I/CV/CV/CP and so forth but the instructions were very vague on utilizing M1, M2. I watched a ton of U-tube videos on these modules but none covered M1/M2.

« Last Edit: October 07, 2017, 07:33:21 am by retrolefty »
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #39 on: October 07, 2017, 06:41:04 am »
I milled a front panel. It is for a cheap eBay aluminun case. You can cut it in half and use it for two modules. I can share the gerber files if anyone is interested. I'll make the back panel next week. The back panel got different DC inputs like banana, Dell laptop PSU and regular DC jack and on/off switch.

http://www.ebay.com/itm/122209212878
 
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Offline bitseeker

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #40 on: October 07, 2017, 07:30:03 am »
These look ideal for using some of the random transformers I've harvested over the years, seems I may not need to weigh them in for copper scrap.

Yes, a nice way to make the most of stuff that's lying around.
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Offline crx991

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #41 on: October 07, 2017, 08:14:15 am »

nb. The main use for a bench supply usually isn't the variable voltage, it's the current limiting. Limiting the current to {2*$expected} can save many a project from going up in flames.
I Know, an that's the main reason why i would buy one of this...
For example, i've seen that i can easly find a shorted component fixing the current at specified value (e.s. 12v 1a) and i can easly spot the failure finding the hottest component
But sorry i can't understand english very well, so with this device i can't limit current? only voltage?  :-\
 

Offline doobedoobedo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #42 on: October 07, 2017, 08:41:00 am »
I made a battery powered supply from a 3003 a while ago. powered by a 3S LiPo


edit: probably best to post the photo instead of the edit list  :-DD
« Last Edit: October 07, 2017, 08:55:33 am by doobedoobedo »
 
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Offline jonovid

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #43 on: October 07, 2017, 10:07:32 am »

if you really want to learn electronics, then build it from scratch. just to prove you know your stuff.  :box:
but if your bit of an lazy oldie, like me. or cheapskate then go for it.  :-+ :-+
however as with all things cheap & Chinese, its recommended to derate it's output by 20% IMO.
I may just get one or two and make some for the bench.  ;D
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Offline Red Squirrel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #44 on: October 07, 2017, 11:21:12 am »
I've been stopping myself from buying a premade one for that reason, I want to learn to build my own SMPS one and maybe also a linear.  But I think it might be good to have a "proper" one to start off with so might get one of these anyway.   I think I will feed AC directly in though, and just step down the voltage.  So it will give me a little something to experiment with.   Thinking either a H bridge or push-pull controller and a SMPS transformer to bring the voltage down to like 40 volts or something.   Might do a bunch of separate rails and get more than one of the units and make a multi output PSU.

As a total side note is it just me or is Aliexpress a horrible site to browse?  Every single listing you get one of those annoying modal popups.
 

Offline bitseeker

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #45 on: October 07, 2017, 11:25:33 am »
Yes, AliExpress has been very annoying with the popup coupons for anonymous browsers. It's not smart enough to check its own session cookies, so it keeps showing the popup. If you log in, then it doesn't harass you.
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Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #46 on: October 07, 2017, 12:29:08 pm »
The biggest flaw with these modules is the low side current measurement.

I searched this thread to see if anyone had mentioned that, is it mentioned in the vid, you have to be
ground aware[TM] using one of these. In grounding a metal case which gnd do you connect the case to?
 

Offline Brumby

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #47 on: October 07, 2017, 12:47:29 pm »
They even have USB and Bluetooth communications versions: http://www.ebay.com.au/itm/DPS5005-Communication-Function-Constant-Voltage-Step-down-Power-Supply-Module-AU-/162672153720


Does anyone know if two modules can be easily set up for a tracking split supply?
« Last Edit: October 07, 2017, 12:50:57 pm by Brumby »
 

Offline Rolo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #48 on: October 07, 2017, 05:32:22 pm »
I ordered the DSP3005 with the USB and Bluetooth communication boards. I have no real need for remote control but it's nice to play with. They even have optical isolators on the USB serial board.
On question comes to mind, does bluetooth work trough an aluminium case?

 

Offline German_EE

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #49 on: October 07, 2017, 07:09:11 pm »
Just ordered a pair of 50V 15A versions, I already have the transformers to make a dual power supply. Cost was 45 USD each over Ebay.

The level of ripple and noise should be interesting, I wonder if additional filtering will be needed?
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline raul320

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #50 on: October 07, 2017, 08:06:05 pm »
i have embedded such module in ups case. it works pretty well
 
 

Offline CJay

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #51 on: October 07, 2017, 10:00:10 pm »
i have embedded such module in ups case. it works pretty well

Nice, I have an APC SmartUPS which would work well for that, thanks for the idea
M0UAW
 

Offline electronic_eel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #52 on: October 08, 2017, 03:35:59 am »
When reading about the open source firmware replacement for these units here https://johan.kanflo.com/opendps-design/, it seems like the CC mode control is just done in software by reading the current with the ADC and adjusting the set voltage with the DAC.

Is this true for the stock firmware too or is the open firmware just missing a hardware control loop for CC mode?

How bad is the CC mode with quickly varying resistances? Did anyone test it with an e load with pulse mode?

 

Offline bitseeker

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #53 on: October 08, 2017, 04:13:21 am »
i have embedded such module in ups case. it works pretty well

That is a neat idea, raul. :-+
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Offline ez24

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #54 on: October 08, 2017, 06:58:36 am »
...  I can power it via a Dell laptop PSU ...

How do you handle the "third" wire?   The center pin.

thanks
YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline German_EE

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #55 on: October 08, 2017, 07:25:01 am »
If Dell (or their sub-contractor) have done it right then the center pin or PE should be connected to negative on the output, this means that the chassis of the notebook is then grounded. Notebook supplies are however strange beasts and at least half of them from any manufacturer will have the output floating, with ground only used for the filters on the mains side and maybe the screens.

As a test measure using a 10M impedance voltmeter between negative output and mains earth with the supply running. If you see half mains voltage then your output is probably floating. Note that this voltage is normally quite safe, it's just leakage current from the capacitors.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #56 on: October 08, 2017, 07:45:18 am »
...  I can power it via a Dell laptop PSU ...

How do you handle the "third" wire?   The center pin.

thanks
I leave it unconnected. My workplace uses Dell laptops and all original PSUs have worked fine.
 

Offline Bratster

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #57 on: October 08, 2017, 08:51:19 am »
...  I can power it via a Dell laptop PSU ...

How do you handle the "third" wire?   The center pin.

thanks
That third wire on Dell power supplies is just an ID wire that tells the computer the wattage of the power supply, and if it is genuine.

The power supply itself just sends out power it doesn't care.

Sent from my Nexus 6 using Tapatalk

 

Offline Rolo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #58 on: October 08, 2017, 05:18:10 pm »
When reading about the open source firmware replacement for these units here https://johan.kanflo.com/opendps-design/, it seems like the CC mode control is just done in software by reading the current with the ADC and adjusting the set voltage with the DAC.

Is this true for the stock firmware too or is the open firmware just missing a hardware control loop for CC mode?

How bad is the CC mode with quickly varying resistances? Did anyone test it with an e load with pulse mode?

I have plans to test it with pulsing loads. I think I have the parts laying around to build this:


   
« Last Edit: October 08, 2017, 07:40:35 pm by Rolo »
 

Offline German_EE

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #59 on: October 08, 2017, 07:35:41 pm »
Shariar over on The Signal Path has done some tests as well, he worked on the DPH3205 buck/boost module:

Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline Fungus

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #60 on: October 08, 2017, 09:45:55 pm »
But sorry i can't understand english very well, so with this device i can't limit current? only voltage?  :-\

You can limit current and voltage with these.
 

Offline halexa

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #61 on: October 09, 2017, 12:21:26 am »
My attempt, got it finished 15min before the Patreon video was released.  :scared:

It based on a server PSU that I scored from a dumpster. 240VAC supplied with 24DC output.
I manage to fit the switch-modul, binding post and on/off button in the PSU casing.






 

Offline Rolo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #62 on: October 09, 2017, 01:38:20 am »
My attempt, got it finished 15min before the Patreon video was released.  :scared:

It based on a server PSU that I scored from a dumpster. 240VAC supplied with 24DC output.
I manage to fit the switch-modul, binding post and on/off button in the PSU casing.

Nice, I do like the red panel, witch module did you choose for this PSU?
 

Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #63 on: October 09, 2017, 02:12:50 am »
It based on a server PSU that I scored from a dumpster. 240VAC supplied with 24DC output.

How have you arranged the GNDs between the input, output and case ?

There's some discussion about the DPS's input and output GNDs not being the same starting about here:
http://www.eevblog.com/forum/projects/dps5005-portable-mini-lab-psu/msg1288457/#msg1288457
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #64 on: October 09, 2017, 02:26:52 am »
It based on a server PSU that I scored from a dumpster. 240VAC supplied with 24DC output.

How have you arranged the GNDs between the input, output and case ?

There's some discussion about the DPS's input and output GNDs not being the same starting about here:
http://www.eevblog.com/forum/projects/dps5005-portable-mini-lab-psu/msg1288457/#msg1288457
The Dell laptop PSU got floating output. In that picture the? DPS5005 module is powered from the internal battery.
 

Offline halexa

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #65 on: October 09, 2017, 03:02:37 am »
My attempt, got it finished 15min before the Patreon video was released.  :scared:

It based on a server PSU that I scored from a dumpster. 240VAC supplied with 24DC output.
I manage to fit the switch-modul, binding post and on/off button in the PSU casing.

Nice, I do like the red panel, witch module did you choose for this PSU?

I used DPS5005
 

Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #66 on: October 09, 2017, 03:27:33 am »
The Dell laptop PSU got floating output.

Yep, on a quick check my [Dell + monitor] seems to be floating, just 14VAC when on, 0VAC and OC when off, I didn't measure the current.

Quote
In that picture the? DPS5005 module is powered from the internal battery.

I know yours has battery, have you connected your aluminium case to anything, or just left it floating?
« Last Edit: October 09, 2017, 03:30:12 am by StillTrying »
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #67 on: October 09, 2017, 03:31:35 am »


I know yours has battery, have you connected your aluminium case to anything ?
The case is floating. I'll probably connect it to input ground when I add the optoisolated USB.
 

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #68 on: October 09, 2017, 03:41:06 am »


I know yours has battery, have you connected your aluminium case to anything ?
The case is floating. I'll probably connect it to input ground when I add the optoisolated USB.

That's the problem, if the DPS's +Ve or -Ve outputs come in contact with the case - Boom! - possibly.
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #69 on: October 09, 2017, 03:58:45 am »


I know yours has battery, have you connected your aluminium case to anything ?
The case is floating. I'll probably connect it to input ground when I add the optoisolated USB.

That's the problem, if the DPS's +Ve or -Ve outputs come in contact with the case - Boom! - possibly.
I have not put much thought to it yet. That's why the case is floating atm. I have to check the modules ground path. There is at least the low side current measurement shunt. Floating or connection to output- may be better.
 

Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #70 on: October 09, 2017, 04:03:55 am »
"connection to output -Ve may be better."

Yep. I think the only safe use of these is with the inputs +V and -V floating and isolated from everything else.
« Last Edit: October 09, 2017, 04:06:34 am by StillTrying »
 

Online retrolefty

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #71 on: October 09, 2017, 06:18:37 am »
Does anyone know how to utilize the M functions?

 Appears you can save specific V/I/CV/CV/CP setups and so forth but the instructions were very vague on utilizing M1, M2 functions. I watched a ton of U-tube videos on these modules but none covered M1/M2.

Bump. Has no one mastered the M functions yet?   :-/O
 

Offline HKJ

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #72 on: October 09, 2017, 06:23:51 am »
Does anyone know how to utilize the M functions?

 Appears you can save specific V/I/CV/CV/CP setups and so forth but the instructions were very vague on utilizing M1, M2 functions. I watched a ton of U-tube videos on these modules but none covered M1/M2.

Bump. Has no one mastered the M functions yet?   :-/O


I do cover them in my review I linked before:

The device has 9 preset memories. To save a preset adjust the parameters, move the marker to M0, adjust the encoded to desired preset number and hold down the SET button.

Holding down V/A/SET will recall a preset, with V and A it is preset 1 and 2, with SET any of the 9 presets can be selected.





 

Offline Ertew

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #73 on: October 09, 2017, 09:13:28 am »
My english is poor, but i try to not make mistakes.
 
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Offline bill.coghill

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #74 on: October 09, 2017, 04:45:14 pm »
I'm looking to get a couple of DPS3005 comms version to build some automated testing for a product - was about to press go on a Tenma with USB from Element14 and then try and munge a Python script for control and monitoring !

Protocol for the DPS serial seems to be based on ModBus RTU, but I found some Python code someone wrote that can talk to it easily.
There is some good info about remote controlling them here : http://ls-homeprojects.co.uk/dps3005-psu-module-and-modbus-rtu-python-arduino/

Bill.
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #75 on: October 09, 2017, 05:05:52 pm »


I'm looking to get a couple of DPS3005 comms version to build some automated testing for a product - was about to press go on a Tenma with USB from Element14 and then try and munge a Python script for control and monitoring !

Protocol for the DPS serial seems to be based on ModBus RTU, but I found some Python code someone wrote that can talk to it easily.
There is some good info about remote controlling them here : http://ls-homeprojects.co.uk/dps3005-psu-module-and-modbus-rtu-python-arduino/

Bill.

Here is a translated document about the communication protocol https://drive.google.com/file/d/0B4-iOelpRB0tWjAzUnJZNkVicWs/view?usp=drivesdk
 
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Offline Red Squirrel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #76 on: October 11, 2017, 03:41:06 pm »
Well I caved.  Bought 3.  :P

Alibaba's site was frustrating me with that annoying modal popup but found some on Ebay too: http://www.ebay.ca/itm/RD-DPS3005-buck-Power-Supply-LCD-color-display-step-down-voltage-converter-/292040632850?hash=item43fefa6a12:g:VwEAAOSwImRYXJme

 

Offline bitseeker

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #77 on: October 11, 2017, 04:05:27 pm »
Just log in to make the popups go away. They're for "new" visitors. (Yeah, nice way to welcome someone for the first time, eh? :palm:)
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Offline bill.coghill

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #78 on: October 11, 2017, 04:07:37 pm »
Pulled the trigger on 2.  Lets see how long the 'upgraded' shipping takes....
bill.
 

Offline sempaiscuba

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #79 on: October 11, 2017, 11:19:02 pm »
 

Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #80 on: October 11, 2017, 11:51:14 pm »
I saw the DP20V2A module on eBay this morning for just £1.98 (GB) with free shipping!

I think the DP versions are harder to set V & I.

"This listing (http://www.ebay.co.uk/itm/New-DP20V2A-CVCC-Programmable-Control-Step-Down-Power-Supply-Module-LCD-Display/292005962189) has been removed, or this item is not available."
 

Offline Red Squirrel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #81 on: October 19, 2017, 01:31:56 pm »
Wow that was fast, mine just came in. Did not get a chance to play with it though.
 

Offline dijkmane

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #82 on: October 20, 2017, 07:11:23 am »
i've used the 50V5A version and build it into an old NAS housing. ;





later modified it a bit and build in a temperature controled fan regulator, same as Dave, i don't trust that little cooling piece on it, on full load it gets pretty hot.
« Last Edit: October 20, 2017, 11:55:02 pm by dijkmane »
 

Offline technogeeky

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #83 on: October 20, 2017, 11:31:32 pm »
I saw the DP20V2A module on eBay this morning for just £1.98 (GB) with free shipping!

I think the DP versions are harder to set V & I.


Yep!

With the DP versions, instead of there being different buttons to change V and I, you instead have to switch through all of the places for both V and I every time using the push-in part of the rotary encoder.

 

Offline Brumby

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #84 on: October 21, 2017, 10:56:55 am »
UI Fail!
 

Offline Rolo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #85 on: October 22, 2017, 11:49:01 pm »
My DPS3005 module arrived yesterday. I ordered the "communications" version with the serial and bluetooth boards.





 

Offline Red Squirrel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #86 on: October 23, 2017, 05:32:35 pm »
Finally got round to testing one of these out (I got 3 lol). Busy with lot of other projects atm but my goal is to build a multi output psu box, will throw in a few fixed linear regulators in there too for good measure.

I'm giving myself a bit of a challenge though, I could easily stick it in a box with a plug pack and call it a day, but I want to do my own mains conversion stage too.  I still need to experiment with high frequency transformers as my last attempt involved lot of back EMF and rather low power output.   I will probably cheat and just use arduino and a push-pull setup with a centre tap transformer.   What I'd like to do is multiple output windings so each psu module can be isolated from each other. 

Speaking of isolation, it's probably obvious given the lack of transformer on it, but these are not isolated, and an interesting effect I tested is if you short the positive to a ground other than it's output, it just shorts out with maximum current.   Makes sense as that would bypass the current shunt.  Something to keep in mind though.
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #87 on: October 23, 2017, 10:40:38 pm »
Latest two units look like this. All inputs are parallel (banana female, Standard DC 5.5*2.1mm jack, Dell laptop jack). USB is for the modules communication (optoisolated UART through USB). Front cover have been milled with a PCB router.

 

Offline technogeeky

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #88 on: October 24, 2017, 10:10:38 pm »
Latest two units look like this. All inputs are parallel (banana female, Standard DC 5.5*2.1mm jack, Dell laptop jack). USB is for the modules communication (optoisolated UART through USB). Front cover have been milled with a PCB router.



This is one of the places these units really, really shine. They can take any unregulated supply, power pack, wall wart, laptop supply, etc -- and add CC/CV to it (at the cost of ~ 1.5V of dropout and noise).
 

Offline German_EE

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #89 on: October 28, 2017, 05:44:07 am »
I ordered two 15A 50V versions a few weeks ago and they arrived this morning. They're not bad little units but purchasers need to be aware of the following:

1) The front panels are damn small, there's no way I can use them without my spectacles.

2) If yours is a version with a separate PCB then take care with the two cables which are identical. The left connector on the PCB is for the LCD display and the right connector is for the keys. At the display end they are clearly labelled,

3) Turn the rotary encoder slowly and you can sometimes trip up the software. Watch your display.

4) Yes, there is noise and ripple on the outputs, but nothing that an LC filter can't cure.

5) Both of mine ran 13.8V at 10A into an electronic load and were slightly warm after an hour
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

Warren Buffett
 

Offline GreggD

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #90 on: October 28, 2017, 05:59:36 am »
My DPS5005 and DPH3205 Buck-Boost modules arrived 8 days ago. Took 9 days to USA, free shipping.
Could not have been packed better.
I ordered the "communications" version of the 5005 with the USB board costs almost nothing extra.
They both work great. They really did a good job software and hardware.
The PC software, I have not installed it, looks to be National Instruments (NI) stuff and is bloated at 228.8MB.

enjoy !
 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #91 on: October 28, 2017, 06:25:09 am »
My DPS5005 and DPH3205 Buck-Boost modules arrived 8 days ago. Took 9 days to USA, free shipping.
Could not have been packed better.
I ordered the "communications" version of the 5005 with the USB board costs almost nothing extra.
They both work great. They really did a good job software and hardware.
The PC software, I have not installed it, looks to be National Instruments (NI) stuff and is bloated at 228.8MB.

enjoy !
Did you check the Communication Protocol document?
 

Offline Freelander

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #92 on: November 06, 2017, 06:31:54 pm »
Hi Plazma,
My very first post here so big Hi to all.
As said earlier, the Protocol is MODBUS RTU using only  Functions 3,6 and 10. Really really easy to use via remote. The only thing that many would find confusing - I think - is the M-Pre and S-INI.
For info - M-Pre is basically -

From my working notes :-))
6H : M-PRE : Memory Preset Output state selection on recall: Read/Write. Sets or Reads the Memory Preset output state according to the  preceding state of the output. 0 = the output is off regardless of the previous control set state. 1 = output follows previous control set state

7H : S-INI : Power Switch Output State on INITIALISATION only (ie - on a unit reboot): Read/Write. Sets or Reads the Switched Output Control State. (Output terminals active or not)  (ON/OFF). where 0 Is output OFF (Disabled) and 1 is output ON (Enabled).
NOTE – this is ONLY on boot up. This setting is viable as once a  preset memory is recalled it overwrites M0. If the unit is rebooted the last setting is recalled. The output state though is determined by the setting of the S-INI in the group that was last called.

So, if you set M-Pre to 1, then when the memory is called (the M1 to M9, then if the output was enabled on the last memory used, then the output will be enabled immediately on the new memory, if it wasn't enabled on the previous, it wont be on the new one. If set to 0, then on calling that specific memory it will always start with the output off.

S-INI is only for the case where the memory is the last one used. On next start up if S-INI is set to 1 then the output will be enabled. If set to 0 - it won't.

Memory location M0 is basically overwritten immediately ANY memory is called. It is a working area really. If you 'call' M0 then nothing will happen as M0 is whatever you last called. Example - call M8, M8 overwrites M0, (but leaves the contents of M8 as is).

M1 and M2 are special cases in that they can be quickly called from the upper and lower buttons.

There are 512 Words assigned for the Modbus Allocation. Very few are used though. Really well put together Comms and works superbly.

It is a really superb product at a true bargain price. Look out for a new beasty in the near future - a nice shiney new DPH5005. Buck Boost with comms. The DPH3205 is not getting comms afaik, the DPH5005 is the replacement for it. I am working on a battery operated version when parts arrive.
If anyone wants any tips on the modbus rtu comms give me a shout.
Another point worth mentioning - anyone who wants to play comms, you cannot damage the unit by sending a wrong command  - it is bullet proof. there are no 'gotcha's' in there at all. - I specifically tried to break it and it simply isn't an issue.

BR,
- Again, Hi to all and keep up the super work, what an excellent forum !. Joe

« Last Edit: November 06, 2017, 06:40:44 pm by Freelander »
 
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Offline Freelander

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #93 on: November 07, 2017, 04:45:33 am »
My DPS5005 and DPH3205 Buck-Boost modules arrived 8 days ago. Took 9 days to USA, free shipping.
Could not have been packed better.
I ordered the "communications" version of the 5005 with the USB board costs almost nothing extra.
They both work great. They really did a good job software and hardware.
The PC software, I have not installed it, looks to be National Instruments (NI) stuff and is bloated at 228.8MB.

enjoy !

Watch for the NI stuff on WIndows 8.1 asking to 'disable fast startup' - Just completely ignore it - it is a hangover from more complex uses of the NI core software. It is probably the same on Win 10 - the 'ET Phone home OS'  :rant: - but again, just ignore the prompt to disable fast boot. Not needed.
The PC software is actually very good. It is also easy to communicate with the unit via a micro (arduino or pic etc) if needed. Looking at a simple micro to use as a link between two DPS5020C's for tracking and series / parallel.  All good fun.
 

Offline Fungus

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #94 on: November 08, 2017, 08:24:31 am »
I've just ordered mine!

I'm going for a lower power model: Mostly I do 5V stuff with the occasional need for 12V (for big LEDs). I'm after the current limiting as much as anything else.
 

Offline kalel

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #95 on: November 12, 2017, 07:44:33 pm »
I've just ordered mine!

I'm going for a lower power model: Mostly I do 5V stuff with the occasional need for 12V (for big LEDs). I'm after the current limiting as much as anything else.

Let us know your experiences, also, what will you use as supply?
 

Offline Fungus

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #96 on: November 13, 2017, 02:19:25 am »
I've just ordered mine!

I'm going for a lower power model: Mostly I do 5V stuff with the occasional need for 12V (for big LEDs). I'm after the current limiting as much as anything else.

Let us know your experiences, also, what will you use as supply?

I've got a fairly decent little 24V/3A switching PSU for input.

Edit: Hah! I just found it, it actually has a web page:

http://www.smun.com/en/Catalogue/slim%2070w%2024v%20power%20supply-204.html

Extruded aluminium chassis(!) I've abused a couple of them in the past and they've help up perfectly.
« Last Edit: November 13, 2017, 03:06:51 am by Fungus »
 

Offline tzok

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #97 on: November 13, 2017, 02:44:57 am »
One thing in DPS3003 manual worries me:
Quote
If you connect the power supply with output, the module will be burnt.
Does it mean that when I hook up a lead-acid battery to the output (to charge it), and there will be a power outage, my module will release "a magic smoke"?

P.S.
As a 1st stage power supply I'm using MeanWell LRS-100-36, which is a 100W 36V switching power supply.

 

Offline plazma

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #98 on: November 13, 2017, 02:52:26 am »
One thing in DPS3003 manual worries me:
Quote
If you connect the power supply with output, the module will be burnt.
Does it mean that when I hook up a lead-acid battery to the output (to charge it), and there will be a power outage, my module will release "a magic smoke"?

P.S.
As a 1st stage power supply I'm using MeanWell LRS-100-36, which is a 100W 36V switching power supply.


It may be if the module is not powered on when connecting a battery at the output. If it is powered on then it does not fry.
 

Offline StillTrying

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #99 on: November 13, 2017, 03:17:01 am »
"If you connect the power supply with output, the module will be burnt."

I always take that to mean that you can't let either of its output connections come into contact with the input (power supply) connections, because of the low current sense. Input and output GNDs connecting is the problem.
 

Offline ChrisLX200

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #100 on: November 13, 2017, 05:53:38 am »
This may be a dumb question but.. when I checked the output of my DPS5015 there was 30mV ripple (@  68Hz), that's with 15v nominal output and 2A. I tried placing a 470uf/63v capacitor across the output and the ripple disappeared to something negligable. Tried a 100uF and the ripple was only reduced to 25mV. Would it be OK to run it with the 470uF cap or is it going to burn my circuits when the power is switched off? I assume the stored charge has to go somewhere :)

(in the photo below the display refresh on the electronic load is slow, it actually reads 14.9?V and 2.00A)

 

Offline Kleinstein

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #101 on: November 13, 2017, 06:50:48 am »
A 470 µF is rather large, but not unusually large for a power supply of that power range. I would not expect the current limiting of this supply to be very fast either, so the extra charge from the 470 µF would not change that much. If at all the extra cap makes a difference on a short or on load transients, not during turn off.

A 68 kHz ripple frequency would be rather low for the switched mode supply. The load looks like an electronic load. If either the load or the supply is not really stable with difficult load, there is a chance the 68 kHz is due to the supply and load not working well together. There are chances that the load is the culprit.
 
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Offline ChrisLX200

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #102 on: November 13, 2017, 08:02:23 am »
Thanks! I'll try using a 50w power resistor as the load and see what happens, it whould be OK for a few minutes without overheating.

edit: result was the sme ripple frequency, larger ripple (35mV) and way reduced effect of the 470uF cap (down to about 20mV, so less than half reduction). The PSU output was 5A and lower voltage  because the resistor is only 1 Ohm.
 

Offline Fungus

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #103 on: November 13, 2017, 08:51:41 am »
...way reduced effect of the 470uF cap (down to about 20mV, so less than half reduction). The PSU output was 5A

Not surprising the capacitor was too small with a 5A load. 5A will drain the capacitor in no time when the voltage dips.
 

Offline ChrisLX200

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #104 on: November 13, 2017, 09:21:01 am »
I guess so. I will stay with the 470uF though, if I really need a 5A output I won't be reaching for this device :)
 

Offline emax

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #105 on: November 16, 2017, 05:06:39 am »
Hm, I ask myself, whether it wouldn't be possible to "abuse" such a module as an electronic load?

I have to discharge LiIon batteries from rc airplanes from time to time. If I'd attach these batteries on the input side of the module (as a source) - shouldn't it be possible to adjust the discharging - current on the output-side for a controlled discharging of the batteries? Burning the power shouldn't be a big issue, any piece of constantan, an old toaster or whatever should do.

This is maybe a weird idea, but in absence of a real electronic load, wouldn't t this be an alternative?
 

Offline ChrisLX200

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #106 on: November 16, 2017, 06:21:06 am »
Even if you could it would make little sense when you can buy an item like this: http://www.ebay.co.uk/itm/Constant-Current-Electronic-Load-9-99A-60W-1-30V-Battery-Capacity-Tester-F7/322461010090?epid=934297847&hash=item4b142c88aa:g:hE0AAOSw5cNYQBqA  for little money and is designed for the job. I have one of these and it works well.
 

Offline RD Tech

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #107 on: December 02, 2017, 07:59:16 pm »
In one of the threads on these modules (here) around nine months to a year ago, I think the OP had figured out how to make the modules externally programmable.

Anyway, at some point the OP of that thread discoverd some glitch in the device which suddenly caused the voltage to become uncontrolled, and I think caused some kind of problem. I don't think this was in the standard use case, so it likely does not matter to viewers just looking for a power supply.

Also, this was a while ago so its entirely likely that whatever the glitch was the manufacturer may have fixed it.

I will try to find the exact link. This was when I was looking for a good power supply so I may have even bookmarked it.
what's wrong ? the products was damaged? please contact me by email 1749808660@qq.com, I can help you
So, if this glitch was fixed, these supplies may also be a good base for a project to build a programmable CV/CC supply.
 

Offline RD Tech

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #108 on: December 02, 2017, 08:00:17 pm »
thank you for your help , that is our youtube channel. and this is our official store https://rdtech.aliexpress.com/store/923042
 

Offline RD Tech

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #109 on: December 02, 2017, 08:20:41 pm »
I already have a bench top supply based on their DPH3205 buck-boost module. The power source is a Cosel 12V/13A switcher.
good work and nice device
but you should pay attention that the cables should be far way from the capacitor on the power board, because at high voltage and high current , the capacitor can generate interference to affect cable to make display white and blur..
and you can wrap some isolated layer on the cables.
now we have new products DPH5005, are you interesting this ?
https://www.aliexpress.com/store/product/RD-DPH5005-Buck-boost-converter-Constant-Voltage-current-Programmable-digital-control-Power-Supply-color-LCD-voltmeter/923042_32840324731.html?spm=2114.12010608.0.0.2c41b07bqrupYS
 
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Offline RD Tech

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #110 on: December 02, 2017, 08:23:35 pm »
 

Offline vladovg

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #111 on: December 07, 2017, 08:10:31 am »
I did not like the cheap plastic look so i came up with this.
 
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Offline Brumby

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #112 on: December 07, 2017, 01:29:19 pm »
Very neat - except for the four mounting screws for each module.  If you can't hide them, then they need to be a little more "industrial", IMHO.  Maybe a small, knurled head?

But aside from that minor quibble, it is certainly appealing.

All it is missing is an earth terminal - and dual tracking capability.
 

Offline ez24

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #113 on: December 07, 2017, 02:56:02 pm »
I did not like the cheap plastic look so i came up with this.

Very nice
YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline Dismounted

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #114 on: December 07, 2017, 04:04:54 pm »
I also just finished building a little enclosure around two DPS5005 modules. :D
 

Offline ez24

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #115 on: December 07, 2017, 04:10:29 pm »
I also just finished building a little enclosure around two DPS5005 modules. :D

Another nice job  :-+  Wish I could do the same.  Be proud
YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline Brumby

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #116 on: December 07, 2017, 06:08:58 pm »
HAH!!  I have that same case ... and my vision is almost identical.

It's just waiting for a couple of those modules.
 

Offline Dismounted

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #117 on: December 07, 2017, 10:25:08 pm »
HAH!!  I have that same case ... and my vision is almost identical.

It's just waiting for a couple of those modules.
Nice! What do you plan on using to provide the input power? I've currently got two ThinkPad laptop chargers in there.
 

Offline Brumby

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #118 on: December 07, 2017, 11:15:56 pm »
Haven't planned that far ahead yet.  Will be going through my box of transformers to see what I might have that will fit.  If not, then it's onto the other boxes of stuff....
 

Offline ocw

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #119 on: December 30, 2017, 03:43:14 am »
Having purchased several of the low cost power supply modules and with a bunch of extra thumbwheel switches, I thought that I'd make my own version.

Attached is a picture of the voltage regulator/metering circuit which I just constructed.  I used a LT3080 1.1 amp regulator for my first try.  I might also build a 3 amp LT3083 version.  The display shows the voltage in red and the current in blue.  The side switch changes the voltage display between measuring the output and input voltages.

It doesn't have current limiting but does make it easier to change the desired voltage.  It's somewhat a combination of old and more recent technology.  It is just a spare time project to test the IC.
 

Offline ez24

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #120 on: December 30, 2017, 05:45:45 am »
Having purchased several of the low cost power supply modules and with a bunch of extra thumbwheel switches, I thought that I'd make my own version.

Nice job.  How did you mount in the case?  I have some of these meters.  I assume it is a 5 wire meter, 4 digit.  Do you use one or two power supplies?  I am trying to figure out the advantages of using one or two supplies.

Here is the meter I have (has wiring diagram)
https://www.aliexpress.com/item/Digital-4-Bit-DC-200V-0-10A-Voltmeter-Ammeter-Red-Blue-LED-Dual-Display-Built-in/32586815094.html

Here is one buck I bougnt. Real crappy, at 12v @ 3a it has 2vpp ripple and a loud singing noise
https://www.aliexpress.com/item/300W-20A-DC-DC-Buck-Converter-Step-Down-Module-Constant-Current-LED-Driver-Power-Step-Down/32841643698.html

Here is the buck I am going to use (my scope crapped out just as I saw little ripple so no measurement) :
https://www.aliexpress.com/item/DC-CC-9A-300W-Step-Down-Buck-Converter-5-40V-To-1-2-35V-Power-module/32824805142.html


Testing is a real pain in the butt so I ordered this (not received yet):
https://www.aliexpress.com/item/8-in-1-150W-Digital-battery-capacity-tester-voltmeter-adjustable-constant-current-electronic-load-charger-usb/32830145151.html

thanks






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Offline ocw

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #121 on: December 30, 2017, 06:58:25 am »
Quote
How did you mount in the case? ...  Do you use one or two power supplies?

With the LT3080 regulator that I used rated for a maximum input/output voltage of 36 volts, I thought that I could live with the minor limitation of using the similar 33V 3A meters that a lot of people have on eBay:

https://www.ebay.com/itm/Dual-Display-4-Bit-Voltage-Current-Meter-DC-0-33V-1A-3A-Voltmeter-Ammeter/282275457510?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The trimmer resistor on those is used to calibrate the current reading.  I used a Bud CU-793 enclosure.  I used relatively primitive methods to cut rectangular holes for the meter and thumbwheel switches.  Since I already have a bunch of regulated and unregulated supplies, I made it to be used with any single supply.

The voltage and current reading accuracy is mostly a function of the meter.  I'm more concerned on how closely the output voltage to a precision meter compares to the setting on the thumbwheel switches.  They select a single resistor which sets the output voltage.  I generally used 0.1% resistors, sometimes paralleling the resistors to get the precise value desired.  For example, I added a selected 100M ohm resistor in parallel with a 806k resistor to better achieve the desired 800k value.  I have not yet completed the verification of that accuracy.
 
 
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Offline ocw

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #122 on: December 30, 2017, 09:13:23 am »
Quote
I have not yet completed the verification of that accuracy.

I just completed my verification on how well the LT3080's output voltage matched that chosen by the thumbwheel resistor selection.  A typical output reading was under 0.3% off of the thumbwheel value.  I suspect that the few outside of that range were due to my compromise made on the resistor value choice (such as using a 604k resistor when a 600k resistor was desired).

Attached is the accuracy data using my Agilent 34401A as the reference.  The economy meter used had good accuracy as well.  For the tenth of a volt accuracies, I calculated how far the increase in voltage compared with the voltage produced with the thumbwheel set for 10.0 volts.  And with 32 volts input and the LT3080 set for a 1.0 volt, the output voltage was about 6.7% high.  However, with an input voltage of 10 volts with that setting, the 1.0 volt output was just 0.03% low.
« Last Edit: December 30, 2017, 10:24:53 am by ocw »
 

Offline analogo

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #123 on: December 31, 2017, 12:39:55 am »
4) Yes, there is noise and ripple on the outputs, but nothing that an LC filter can't cure.

Moin German_EE, how much noise and ripple have you experienced?

With which model?
 

Offline pelrun

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #124 on: February 17, 2018, 05:46:11 pm »
I've got a basic Sigrok driver written for these devices that I'll be submitting upstream shortly, but I've hit a minor sticking point.

The protocol has a MODEL register (0x0B) that identifies which device is connected, but the documentation doesn't provide any information about what each device actually has here. My DPH5005 returns 5205, so it's not a perfect mapping to the model number (although that may be just due to a name collision with the DPS5005.) I tried asking the company directly and hit a language barrier.

If anyone with a comms-enabled device other than the DPH5005 is in a position to read out the value from their unit and post it it'd be much appreciated.

(alternatively I could just write off-scale high values for V and I and read back the clamped values, but that's hardly elegant...)

Edit: I got in touch with the guy who translated the protocol doc into English and he confirmed that the register matches the model number for all units *except* the DPH5005, so I'm all set.
« Last Edit: February 18, 2018, 02:58:45 pm by pelrun »
 

Offline PLATIJET

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Re: EEVblog #1030 - $20 DIY Bench Power Supply!
« Reply #125 on: November 29, 2018, 07:27:52 am »
Any better or newest software with Voltage/Current curves record/export?
 


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