Author Topic: EEVblog #1030 - $20 DIY Bench Power Supply!  (Read 21895 times)

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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).
 

Offline 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.
You don't acquire TEA. It acquires you.
 

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
Hobby of evil genius      basic knowledge of electronics
 

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.
You don't acquire TEA. It acquires you.
 

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 »
 

Online 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?

 

Online 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?
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