0-30V 2mA - 3A power supply DIY kit - Page 1
Forum section: electronics / testgear

author: freebil
author_rank: Regular Contributor
timestamp: May 27, 2016, 08:48:01 am
content: Hello. I am thinking of buying this kit from banggood or ebay. The problem is that I have only a 12v transformer. The kit requires 24v transformer to work but they are expensive(I think 25 euros). Can I use the 12v transformer? I dont mind If the output will be 0-12 or 0-15v. The other thing that I can do is convert atx power supply to bench power supply. As you understand I have no money now for something better. What would you suggest?PS:Thisis the manual for DIY kit with circuit diagram.

author: ebastler
author_rank: Super Contributor
timestamp: May 27, 2016, 10:32:49 am
content: As you are probably aware, the regulator you are looking at buying will only regulate down -- so if you supply only 12V AC at the input, the output will be limited to 15V max or so. With that limitation, using a 12V AC supply should work.On the other hand, maybe you can obtain a 24V AC transformer for free from some scrap consumer device (old audio amplifier or whatever)? You just need the bare transformer (plus fuse).

author: Athanasis
author_rank: Contributor
timestamp: May 27, 2016, 10:41:52 am
content: I would never build something that already exist. I decided to stop doing this. Pay some extra and buy something like this:

author: ebastler
author_rank: Super Contributor
timestamp: May 27, 2016, 12:11:28 pm
content: Quote from: freebil on May 27, 2016, 08:48:01 amQuote from: Athanasis on May 27, 2016, 10:41:52 amHmm... Did you actually read freebil's post?Nothing wrong with building your own power supply, in my view. It is a great entry-level project, results in something that is actually useful, and can save you some money. Go ahead!

author: mos6502
author_rank: Frequent Contributor
timestamp: May 27, 2016, 01:34:41 pm
content: The only reason to do it is if you already have the case and the transformer. Buying those new would cost almost as much as a new PSU.As for the Banggood PSU, they're using this circuit:http://www.electronics-lab.com/project/0-30-vdc-stabilized-power-supply-with-current-control-0-002-3-a/This is the forum thread for it, which you should read carefully:http://electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/But, I would just build my own circuit using an LM723. Much simpler circuit, excellent regulation and way cheaper. You can power the LM723 from a voltage doubler. This way you havezerodropout voltage allowing you to make much better use of your low voltage transformer. Using the banggood circuit without modifications would give you less than 10V output with a 12V transformer.

author: TAMHAN
author_rank: Frequent Contributor
timestamp: May 27, 2016, 01:44:12 pm
content: Hi,do you need the ability to limit current?In General, I would shy away from ready made kits and, instead, build the crappe myself out of discrete components. Also, re the transformer, you might want to check AliExpress.Tam

author: Athanasis
author_rank: Contributor
timestamp: May 27, 2016, 05:16:24 pm
content: Quote from: ebastler on May 27, 2016, 12:11:28 pmHi friend and thanks for your great help in my other posts (https://www.eevblog.com/forum/testgear/what-else-can-i-do-with-rigol-ds1054z-appart-from-measuring-waveforms/)It is not only the circuit, it is the box, the buttons, the LCDs, the connectors, and even the legs below the box. If it is your primary bench PS, you need it to sit perfectly on the bench and help you as a tool towards your other work. It depends on your time and your budget of course but if you want to jump start into real electronics then you need to treat the Multimeter, Soldering iron, Frequency Generator, Oscilloscope and Power Supply as a set of tools and not as your final goal.Building a Power Supply (not the primary bench one) is still a project though that has multiple levels of complexity.

author: Yansi
author_rank: Super Contributor
timestamp: May 27, 2016, 05:21:58 pm
content: The circuit used in the kit in post #1 is a well known garbage, which has flooded the electronics hobby. The circuit has a series of fatal flaws and can never be usedsafelyin the whole output range the circuit was rated at. Nor can it ever work properly in that range.

author: freebil
author_rank: Regular Contributor
timestamp: May 27, 2016, 05:27:57 pm
content: Thank you all for your answers. I only need 0-15v and 0-1A. I have to spend 40 dollars maximum. I findthisfrom ebay but I saw reviews that it is unacceptable. So, I think that I have to build one in my own. I will use it for arduino and staff like this. Maybe the atx psu conversion is the best for me?Something likethismaybe? Is it linear?

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: May 27, 2016, 06:26:10 pm
content: If you want to build a supply yourself as a learning experience that is great. Do it. If you are trying to save money you may be better off just buying a prebuilt cheapy.For Arduino, etc. you really want a current limiting supply. This will save you from burning up as many components. (trust me...) When you fry a few $5 chips in a row it starts to add up.Any of these cheap power supplies are adequate for basic tinkering:http://www.ebay.com/itm/5A-30V-DC-Power-Supply-Adjustable-Dual-Digital-Variable-Precision-Lab-Grade-/262294040786?hash=item3d11f170d2:g:pK0AAOSwWTRWw8EhAre they great? Not at all. Will they last more than a few years? I doubt it. But they do the current limiting and are generally good enough.You have to remember a lot of people reviewing things and giving advice are professionals. You would expect a Forumla 1 driver to tell you a Kia is a piece of crap. You expect pros to tell you this is crap. But just like you don't need a Forumla 1 car to get to the store, you don't need a $300+ power supply to tinker with Arduinos. Save that money for a scope.You might also look for used higher quality supplies. Old Lambda supplies are really solid and can be had for not much money. Things from the 70s and 80s tend to be more user serviceable. Once you get to the 90s and behind there are a lot of custom chips (especially in HP gear) that you just can't fix. But with older gear you will likely need to do some repair, which takes time away from the Arduino stuff. (Repair can be addictive, though.)Good luck.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 27, 2016, 06:55:08 pm
content: The kit circuit might not work proper with a 12 V transformer, or might need a modification (larger cap) for the negative supply. However the suggested 24 V transformer is not a good idea either, as this is too much for the OPs and maybe other parts. So something like a 18 v transformer would be the right type. As the circuit uses a charge pump for a negative supply, the circuit will not directly work with an DC supply. So some modifications (use -12 V instead of charge pump) needed to make it work with a PC supply. However the output voltage is than rather limited unless the OPs are changed.Unless you have a case and transformer it might be cheaper to buy a full cheap supply and reduce the maximum current setting. Often these cheap supplies can not stand the full current for very long - so using only 50-70% of there rated current can help them to last longer.A good starting point for used parts would be an old audio amplifier in the 50 W range.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 28, 2016, 12:02:07 am
content: Quote from: Athanasis on May 27, 2016, 10:41:52 amYou have one of these? How good/bad is it at turn on/off?

author: ebclr
author_rank: Super Contributor
timestamp: May 28, 2016, 12:46:24 am
content: If you have a 12V transformerBuy 1 one thishttp://www.aliexpress.com/item/IN4007-bridge-rectifier-AC-turn-DC-power-adapter-Full-wave-rectifier-circuit-board-suite-components/32658930937.html?spm=2114.30010308.3.2.bFjokc&ws_ab_test=searchweb201556_8,searchweb201602_4_10037_10033_507_10032_10020_10017_10021_10022_10009_10008_10018_101_10019,searchweb201603_3&btsid=aee76cc2-2e4b-4933-acd8-7526db907e87And one of thishttp://www.aliexpress.com/item/LM317-DC-Linear-Converter-Down-Voltage-Regulator-Board-Speed-Control-Module/32564548845.html?spm=2114.13010208.99999999.349.qg2dvUAnd you done

author: ebclr
author_rank: Super Contributor
timestamp: May 28, 2016, 12:49:49 am
content: This one is even better for very low pocketshttp://www.aliexpress.com/item/LM317-DIY-Kit-AC-DC-Input-5V-35V-to-1-25V-30V-Step-Down-Power/32555498638.html?spm=2114.30010308.3.296.LdogBE&ws_ab_test=searchweb201556_8,searchweb201602_4_10037_10033_507_10032_10020_10017_10021_10022_10009_10008_10018_101_10019,searchweb201603_3&btsid=a18535aa-b372-4a2b-ba3d-e1a1af997784