Author Topic: Looking for a bench power supply  (Read 12086 times)

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Offline skyjumper

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Looking for a bench power supply
« on: October 03, 2018, 11:05:17 pm »
I need a power supply for my bench, but don't want to break the bank. I mostly play with digital stuff, so ideally it could do 3.3V, 5V and 12V. Suggestions?
 

Online tautech

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Re: Looking for a bench power supply
« Reply #1 on: October 03, 2018, 11:16:31 pm »
Single or multi-channel ?
10mA/mV precision or better ?
Low noise/ripple = a Linear PSU or will a cheap SMPS suffice ?

Siglent have a few models that will suit your needs:
https://www.siglentamerica.com/power-supplies/
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Offline Doctorandus_P

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Re: Looking for a bench power supply
« Reply #2 on: October 03, 2018, 11:41:58 pm »
If you want to go "cheap" then you can always build something yourself, but that very easily consumes a disproportionate amount of time.
A "decent" power supply has  an adjustable voltage and current limit, although, for low voltages I tend to fall back on 5V USB "charger" power supplies. These vary widely in quality. They do not have an adjustable current limit, but because of the low voltage and (often) 1A or 2A limit usually nothing too bad happens.

As an alternative you can search for "DPS5005" on Ali / Ebay / China / Etc.
This is a quite decent and capable building block to build a power supply.
You can combine it with some laptop brick if you only want low output voltages, or add some transformer & bridge recifier & Elco's. The power supply section of some old audio amplifier is quite usable for these little critters.
DPS5005 accepts voltages upto 50 V, but the input voltage must also be about 10% higher than the output voltage.
DPS5005 has a color TFT lcd, there are also simpler versions with 7-segment displays, but these also do not have encoders but pushbuttons as user interface. This is a bit fiddly. But with opendps (see below) you can add whatever UI you want.

There is also a DPH series of power supply blocks from the same manufacturer. These can step the voltage up or down.

Also noteworthy is the "opendps" project, which has alternative firmware for the STM32 uC in these power supplies.
 

Offline coromonadalix

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Re: Looking for a bench power supply
« Reply #3 on: October 04, 2018, 02:35:38 am »
Budget ???

Personally i would go for any linear model in the Mastech Gw Instech or Hyelec series since manuals and schematics are available ...  find an schematic before you buy, it may help in the future ...

My 2 cents


I was just lucky to find/score  an Kikusui PAD70-5L  on Ebay for 60$, very silent fan, scr phase controlled linear model, very compact size, but 27 pounds  loll
I love the current limit switch to set the value, but no schematics :(
 

Offline skyjumper

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Re: Looking for a bench power supply
« Reply #4 on: October 04, 2018, 06:19:41 am »
Single or multi-channel ?
10mA/mV precision or better ?
Low noise/ripple = a Linear PSU or will a cheap SMPS suffice ?

Siglent have a few models that will suit your needs:
https://www.siglentamerica.com/power-supplies/

Dual channel would be nice but I expect those will be more expensive. The Siglent supplies look nice but start at about $250...
 

Offline skyjumper

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« Last Edit: October 04, 2018, 07:00:35 am by skyjumper »
 

Online HKJ

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Re: Looking for a bench power supply
« Reply #6 on: October 04, 2018, 07:16:27 am »
I have tested/reviewed some of the DPS/DPH power supplies:

https://lygte-info.dk/review/Power%20DPS5020-USB%20UK.html
https://lygte-info.dk/review/Power%20DPH3205%20UK.html
https://lygte-info.dk/review/Power%20DPS5015%20UK.html

That will give a good impression of what they can do.

 

Online nctnico

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Re: Looking for a bench power supply
« Reply #7 on: October 04, 2018, 07:43:10 am »
Switching power supplies are nice for when you need a lot of power but they also output a lot of noise on the outputs which make it difficult to measure signals in a circuit. For generic bench use I'd recommend a PSU with a linear regulated output. A used one could be a good option as well.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online tautech

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Re: Looking for a bench power supply
« Reply #8 on: October 04, 2018, 07:44:59 am »
Single or multi-channel ?
10mA/mV precision or better ?
Low noise/ripple = a Linear PSU or will a cheap SMPS suffice ?

Siglent have a few models that will suit your needs:
https://www.siglentamerica.com/power-supplies/

Dual channel would be nice but I expect those will be more expensive. The Siglent supplies look nice but start at about $250...
After having a few cobbled together and cheap PSU's you will appreciate what goes into making a good PSU.
You have to work out what you'd be happy with as things like power ON overshoot can really ruin your day.
A switchable output is desirable rather than an mains ON/OFF unless you can be sure there's no power ON spikes.

If you are happy to manage with a bit of ripple these SMPS 30V 5A units can be pretty good:
https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/
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Offline VEGETA

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Re: Looking for a bench power supply
« Reply #9 on: October 04, 2018, 07:45:56 am »
The easiest way is to build one yourself from already existing modules.

One AC-DC converter (24v and amps as you like).
One Buck converter module to get 0.5-24v output.

If you want current limit then you can add it with minimal efforts such as greatscott video.

Plus, get a nice enclosure.

This won't cost you more than 30$ if not less.

Offline TERRA Operative

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Re: Looking for a bench power supply
« Reply #10 on: October 04, 2018, 02:00:12 pm »
I was just lucky to find/score  an Kikusui PAD70-5L  on Ebay for 60$, very silent fan, scr phase controlled linear model, very compact size, but 27 pounds  loll
I love the current limit switch to set the value, but no schematics :(

I guess you found this already? Not much in the way of schematics though..
https://www.kikusui.co.jp/php/catalog_lib.php?model_name=pad&skip=190
https://www.kikusuiamerica.com/man/?MODEL=PAD*L&skip=44
https://www.kikusui.co.jp/manuals/index.php?MODEL=PAD70-5L

Give me a bit, I'll send an email to Kikisui Japan (in Japanese) and see if I can convince them to go brave the leopard guarding the filing cabinets in the disused lavatory and have a look for it.
« Last Edit: October 04, 2018, 02:02:10 pm by TERRA Operative »
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.

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Offline Old Printer

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Re: Looking for a bench power supply
« Reply #11 on: October 04, 2018, 02:35:07 pm »
I have done very well on ebay with used equipment. Get something well built and be sure the service manual and schematics are available. I bought a few of the little HP6216A's good to 25V at 500 Mah. I have a stack of three of them, usually under $50 each, sometimes less. If you take your time there are good deals to be had, if the bidding goes up pass and look for another one.
 

Offline bicycleguy

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Re: Looking for a bench power supply
« Reply #12 on: October 04, 2018, 04:51:05 pm »
I really like this power supply, the Tekpower TP3005D-3.  It's over your budget at $199 but it's worth it.

https://www.amazon.com/gp/product/B00HX0UYBK/ref=od_aui_detailpages00?ie=UTF8&psc=1

Here's what I most appreciate:
1. Indestructible, quality construction.  Turn it on full blast, short it out, let it sit.  No problem.
2. With constant current and or voltage you won't destroy what your powering.
3. You can get most any DC motor moving.
4. Quite, fan is temp controlled.
5. Toroidal transformer, linear, low noise.
6. Four nice looking, accurate meters, and so pretty I often turn the supply on unused and think I can't believe I own this!

I don't know why I used my Heathkit IP-2718 Try-Power supply for 30+ years.
 

Offline Candid

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Re: Looking for a bench power supply
« Reply #13 on: October 04, 2018, 05:28:36 pm »
I like this one:
https://www.eevblog.com/forum/testgear/inside-the-new-korad-ka3305p-linear-psu/

It's the bigger model of the one you listed. With this you could do all the voltages you requested at one time.
 

Online Kleinstein

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Re: Looking for a bench power supply
« Reply #14 on: October 04, 2018, 07:11:52 pm »
Those cheap Chinese made linear supplies are usually a little optimistic about there power handling capability. So ideally one should avoid using more than about 2/3 of the rated current, especially for longer time.

Some supplies might show voltage spike on turn on / turn off. So beware of this and maybe check reviews and may check you unit before use. Those spikes are especially bad if one does not know about them.

Normal digital experiments tend to not need a very high current.
 

Offline coromonadalix

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Re: Looking for a bench power supply
« Reply #15 on: October 04, 2018, 08:40:30 pm »
As i wrote on another thread, i'm still doing battle in an Mastech (clone - HY3010E-2) smps model, damn, it is not easy to service even with the schematics, the main pcb is a nightmare to manipulate. I would not consider purchasing this model ever again.

For my new Kikusui PAD70-5L  i'm going to torture it a little with inductives and capacitives loads to see how it react, since it is an scr bridge "phase controlled" psu inside ... never tried this technology, it has half the weight and half the size of my Kepco ATE75-8,  27 pounds vs 56 pounds ???


As the other threads    Evaluate your needs

Kleinstein is right, we have many chinese psu's at my job, they have caused many problems. Quality and power handling is not good at all. Had to switch to Meanwell products, no problems since.
 

Online nctnico

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Re: Looking for a bench power supply
« Reply #16 on: October 04, 2018, 09:54:25 pm »
Some random HP power supplies from Ebay:
https://www.ebay.com/itm/Agilent-HP-6203B-Precision-Power-Supply-80W-Harrison/362444971789
https://www.ebay.com/itm/HP-6284A-DC-Power-Supply-0-20-V-0-3-A-Amperes/372113801431
There are many more power supplies from HP for less than $100 on Ebay. Making an offer below the asking price is likely to land a good deal.

Take note of Kleinstein's remark about power-on / power-off spikes on the output. Less well designed power supplies may suffer from that and can cause serious damage. At one of my previous employers somebody had tested 30 (or so) boards with a power supply which had a power off spike. It took replacing all the chips from every board to get them to work again. I put the power supply in the trash when the boss didn't look.
« Last Edit: October 04, 2018, 10:04:37 pm by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline tkamiya

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Re: Looking for a bench power supply
« Reply #17 on: October 05, 2018, 12:54:40 am »
If you really really want cheap, I have some HP ones you can have.  You have to come to central Florida to pickup yourself though.  They are rugged and reliable.  But also heavy and bulky.
 


Offline Old Printer

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Re: Looking for a bench power supply
« Reply #19 on: October 05, 2018, 02:20:38 pm »
I have had very good luck with these BK Precision 1651 power supply's on eBay. They are solidly built and quiet, no fan, and pretty reasonable. I have picked up three of them so fan under $50 each including shipping. Tektronix also sold it as their CPS250 and wrote a very good service manual that is available for $15 on CD.
 
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Offline skyjumper

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Re: Looking for a bench power supply
« Reply #20 on: October 06, 2018, 04:22:55 pm »
Thanks everyone, these are all great comments. I got tied up at work the past several days but my hunt will resume. Some of the options posted look nice, thank you.
 

Offline Johnboy

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Re: Looking for a bench power supply
« Reply #21 on: October 06, 2018, 05:22:18 pm »
I'm probably talking out of turn, but there have been so many of these threads recently that I thought I'd share my opinion as someone who's had a lot of the same questions.

There seems to be a consensus that older used gear is actually of better design and manufacture than the current, inexpensive new models, especially in terms of the quality of components used in construction. The implication is that those modern PSU's are manufactured or even "built down" to provide a similar [competitive] price point with the older stuff that's still available. Failures can happen, whether old or new, but the older (often linear) designs seem to be simpler (or at least more intuitive) and therefore easier to repair. The tradeoff between older and newer models at the same price point is often modern digital meters (as opposed to analog) for current and voltage, coarse and fine controls, and switching over linear (more efficient, but also often noisier). The newer switching supplies generally involve more parts, so that there are more things to fail, if they do fail. For the OP who seems to want something only for digital purposes, and is content with only 3.3V, 5V, and 12V, a truly variable power supply might actually be overkill for the present need. The modifications to an ATX power supply could provide all these, if it's the right design. Conversely, there is also a tradeoff in using a cheap old ATX garbage-rescue also; they aren't designed to be repurposed in this way and so there are a number of hurdles (including safety) that should be taken into account before going that route (limiting current, et al.).

I did a lot of looking into this while considering what I needed, and I'm still on the fence about the options (redundancy of functions might be the best tradeoff for me). As yet, there doesn't seem to be a "perfect" choice that will suit every entry-level hobbyist. To me (and take this with a grain of salt, as I'm no engineer, just a consumer), it seems to really depend on limiting your choice based on what you're going to do with it, which applications you'll potentially need down the road and whether you'll still be able to find a use for that same model then, or at least that it might hold some of its value when trading up. The other option is to buy something expensive and new from a "big" manufacturer that "does it all", but then you are paying for a great number of features that you well might never use in any application (and there doesn't seem to be a medium ground, they are a very expensive step up if you're used to using 9 volt batteries to power your projects).

The constant advice as alternative seems to be to "build your own", but I've come to the conclusion that I'm not personally competent enough to choose a 'good' design, especially considering that the designs that are often suggested often seem to have hidden design problems (overshoot, etc.) despite their vaunted simplicity.

There have been a lot of threads lamenting the absence of any decent DIY PSU kits left on the market. There are a few, but they all seem to require a lot of modding and extra work to bring the features up to date with modern expectations for performance, and the BOM for components and considerations of additional time involved basically bring them up to the same price point as buying a completed model. There is a gap there, one that I wish would be filled by an enterprising designer; if I could buy a kit that would allow me to learn more about design while also constructing a model with competitive features, I would go that route instead of buying something I don't know how to fix without having access to service manual/schematic and a bunch of repair videos helpfully posted by others with a (hopefully) similar dilemma.
 

Online HKJ

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Re: Looking for a bench power supply
« Reply #22 on: October 06, 2018, 07:16:50 pm »
If you are in the US you can often get used equipment at a very good price, but in other countries it is more difficult.
Then the cheap options are Chinese equipment, that often works fairly well, the other options is more expensive equipment from western companies (It might still be made in China).
Most of my power supplies are from TTi, they are fairly cheap for the quality they offer, but cannot match a newer Keithley supply I have (My only problem with Keithley is fan noise and that includes not only the power supply).
 

Online nctnico

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Re: Looking for a bench power supply
« Reply #23 on: October 06, 2018, 07:55:14 pm »
There seems to be a consensus that older used gear is actually of better design and manufacture than the current, inexpensive new models, especially in terms of the quality of components used in construction.
Since I suggested buying a used power supply let me elaborate a little bit on used power supplies. One of my worries about cheap power supplies are power on/off spikes, temperature stability and usually they don't have multi-turn pots. A used power supply from an A-brand is often nicer unless it is a really old boat anchor which needs a complete rebuild before using. You have a point about digital read-outs but more often than not these aren't very precise/accurate on cheap power supplies so there is no advantage over having analog needle meters. For example I used to own a cheap Conrad bench PSU. This had a 3 digit readout for the voltage for a 30V range. Ofcourse I modified it to have a multi-turn potmeter but I still needed a DMM to adjust the output precisely (for example 1.8V).
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline coromonadalix

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Re: Looking for a bench power supply
« Reply #24 on: October 07, 2018, 03:25:37 am »

There seems to be a consensus that older used gear is actually of better design and manufacture than the current, inexpensive new models, especially in terms of the quality of components used in construction.


The simple answer is : They had Quality at heart,  now they have obsolescence in mind and make some cash, that's all

Just heard back of Kikusui for my Pad L serie psu, they where made in 2002,  support ended in 2016, and this puppy is incredibly well build with very good components quality and robustness, i'm very impressed,  just received complete schematics under NDA.

Now i understand the scr bridge rectifier topology, reduced thermal waste and better efficiency. Recalibrated the meters and zero current and voltages offsets, damn good.

My other Kepco is very well built too ... i hacked it with 4 1/2 digits meters, replaced the 2x front pots with 10 turns pots, but this one was totally recapped.


My opinion :  Old stuff where better designed for durability than most of the present equipment. Lots of old equipment threads end fine after some recapping and sometime small repairs if you dont have any obtanium parts ...

I try to avoid any cheap China stuff for precise / important operations. You know what you've paid for, had too many problems in the past. Tried once Again to degug my Mastech psu, pfff  i think i'll toss it away.

I admit : The Kikusui psu was the first one outside America stuff i've bought, but i had heard good words for this brand of psu's. :)  and the price i've paid was totally worth it.

I even have an 720p definition Daytek 46 inch lcd tv who never had any problems after lots of years of usage, ( +/- 10 years I think)  it was bought at Costco Canada, it does look like an commercial tv, all metal framed, very heavy, no dead pixels, still works fine as today  loll  No one remember this brand in TV, but computer monitors yes loll

 
« Last Edit: October 07, 2018, 03:46:07 pm by coromonadalix »
 


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