Is there an affordable medium level open source DIY lab power supply? - Page 1
Forum section: electronics / beginners

author: Swake
author_rank: Frequent Contributor
timestamp: February 14, 2022, 06:28:21 pm
content: There are some very nice open hardware modular power supplies out there (EEZ H24005) but these are relatively expensive to build, and for most of us also a little too much.Are there any other 'medium' lab power supply designs available?

author: m k
author_rank: Super Contributor
timestamp: February 14, 2022, 06:47:34 pm
content: I think there are so many that you need to put up some numbers.

author: Swake
author_rank: Frequent Contributor
timestamp: February 14, 2022, 09:06:41 pm
content: The idea is to build something myself without necessarily starting from a white paper. There is certainly a good 'modern' design out there.Desired specs are somewhat similar to the Owon P4305.Real floating output somewhere in the region of 0V -> 30V @ 5A. 10mV / 1mA resolution.CV; CV; ideally also OVP/OCP and able to charge batteries (protection);Linear (=low ripple) and a display with set V / C en measured V / C.Series/parallel connectable; tracking with a second one would be ideal.Some memory's to store favorite voltage/current settings.

author: simba15
author_rank: Regular Contributor
timestamp: February 16, 2022, 04:04:31 pm
content: Interested in similar designs.A good linear 0-32v 0-10a supply with CC and CV modes would be great.There are many out there but typically use a switching output (and come from pre assembled parts)Some ideas in the past were base a design from the HP e3610A

author: m k
author_rank: Super Contributor
timestamp: February 16, 2022, 06:00:18 pm
content: 300W is quite serious stuff, 150W is not a miniature either.I've recently tried to find many kinds of things and it seems that ready made bulk stuff it the correct starting point.Even simple mechanical things are either difficult to find or are priced stupidly high.Or if you find something cheap it has a kicker or you need to get a truck load.Power as a product is also quite difficult, everything bulk is already pretty complete.It doesn't feel very sane either to rip off mainly all components from that SMPS panel.Hackaday has interesting front panel RD6006.

author: ledtester
author_rank: Super Contributor
timestamp: February 16, 2022, 06:30:08 pm
content: Quote from: m k on February 16, 2022, 06:00:18 pmI think one big challenge is finding a suitable transformer -- ideally one with multiple taps to avoid having to dissipate a lot of heat.QuoteJust in case you're not aware of it... there is a large thread here on an alternate firmware for the RD6XXX modules:https://www.eevblog.com/forum/testgear/ruideng-riden-rd6006-dc-power-supply/msg3941395/#msg3941395

author: Swake
author_rank: Frequent Contributor
timestamp: February 16, 2022, 10:02:36 pm
content: Plenty of ready made power supplies for competitive prices can be found in many stores. For the hobby these are 99 times out of 100 more than good enough. And yes those Rudeng front-ends are very nice too.But the hobby is the hobby, and what is the electronics hobby if you don't build your own power supplies? In my case every ten years or so something triggers and I build a new one.The idea is that you know how it works, expand and tweak it if you like. Also repair it when it fails because you have all the information and know where to find the components. You can select your own box, add other totally overkill things (small signal generator; multiple channels; component tester; etc) and be proud about it.With a little imagination one can salvage suitable transformers in many places. In old amplifiers for example or 12V and 24V halogen transformers which are replaced by LED's are fairly common. With a 12V/200VA one can build a 15V/10A power supply, and while that voltage might be a little low for some applications, I would build a dual channel version with series/parallel capability or put 2 identical transformers in series.

author: m k
author_rank: Super Contributor
timestamp: February 17, 2022, 04:33:26 pm
content: Sometimes it's good to be a bit late.That other thread was very informative.So one can keep the whole thing, very nice.One issue.Some stuff are isolated and others not.Serial connection can be interesting.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 17, 2022, 06:20:28 pm
content: The ready made versions from china are often priced quite competative. One would have a hard time to get the main parts (case, transformer, heat sinks, ..) for that money, even if one takes into account that the specs are often a bit optimistic.With the higher power targets like 5 A or 10 A one gets to a range where the simple tap switching puts quite some load to the relays. This starts to get to a range where the better design may be a hybrid with a SMPS regulator for the coarse part and than analog for clean up and to get a faster response.For learning and testing I would suggest to build a smaller version with maybe 1 A first and see if it actually works. This can be quite a bit cheaper and an additional small one is often useful too. Scaling up the current is than a relatively simple step.

author: strawberry
author_rank: Super Contributor
timestamp: February 17, 2022, 07:49:36 pm
content: haven't bought transformers from china but they sometimes cheapout too much when things with failed/burned transformers come in for service1.toroid transformers two halves of primaries are wound in parallel to double speed winding process(for 230V high potential between two half)2.too tight winding(wire stretches on corners)3.uneven enamel coating

author: MathWizard
author_rank: Super Contributor
timestamp: February 18, 2022, 01:15:16 am
content: There is definitely schematics out there for older linear BJT and MOSFET PSU's, that are probably pretty good. The main thing is just to spend the money on the actual transformer and hardware.I salvaged a few transformers from 50/100W stereo's, overall they have not been very useful for me trying to make a variable PSU. I should lower the ratings, and then they would be ok. I did use the biggest 1 to make a 0-20V 1A PSU, and it basically works, but I didn't buy the real hardware for it yet, so I haven't built a proper case with plugs, etc.IDK, I have a few transformers from old TVs and stereo's, I just really expected they would be a lot more useful, but I should aim lower, like 10V 0.5A. Or in fact just recyclye them and buy a better trans. for another linear PSU. The I would copy some old design.

author: geggi1
author_rank: Frequent Contributor
timestamp: February 18, 2022, 11:45:05 am
content: First you have to decide what is the maximum voltage you are requiring and the how many amps you need.For most of the smaller electronics you are probably good with voltages less than 15 volts and 1-2amps.If you only need some fixed voltages just go for something like LM7805, LM7812 and other. You can make an fixed 1A output for each voltage.You can even have multiple fixed outputs on the same PSU.If you need a variable voltage you can use a L317 or an L200 voltage regulator. The L200 do have a current limiter function as well.In case you need any higher current you can use a transistor controlled by the voltage regulator. Something like a 2N3055 5A transistor will probably give you more than enough current.For transformer you can go to garage sales, flee markets or any other place you can get used electrics and look for a car battery charger of the old kind with rectifier and transformer.If you find one you can repurpose the transformer, rectifier and probably the current meter if the charger got one. The transformer should not be run at full amperage because some of these transformers are made in a way that will give a large voltage drop at full amperage. Try with about 3/4 of full capacity and check the voltage drop.When you design the PSU try to have the voltage from the transformer 2-3 volts above the maximum voltage yo will need because otherwise you will have more heating of the linear controlling device.Electronic voltage and current meters can be bought on Ebay for reasonable prices and is probably the simplest solution.If you use a second hand car batt charger with metal box the box can probably be repurposed for the PSU.Heat sinks: for the 1 to 2 amp variation you can look in to repurposing old CPU heatsinks with fan from desktop computers. There are probably also capacitors that can be reused in the computer in case you want to go really cheep.For repurposing larger heatsinks you must look into stuff containing power electionics like old HIFI amps, misc drive electronics.

author: wizard69
author_rank: Super Contributor
timestamp: February 18, 2022, 07:25:30 pm
content: Quote from: Swake on February 16, 2022, 10:02:36 pmIt is also a great learning experience for those just getting into electronics. Start out with a simple fixed voltage power supply and work up from there. The goal should be to experience every step of building a suitable product from the electronic design to the final cabinet. At least for me power supplies where the first step into my admittedly limited knowledge of electronics.In your case it looks like you are far from needing a fixed voltage supply. In that regard it might be time to design your own circuit and leave us with a nice open source design. By the way check the manufactures tech notes, data sheets and other docs as there can be insight in those documents.QuoteThat is the point of doing your own design, you can do all the tweaking you like.As for finding components I had to laugh as I've never had so much trouble at work. I seems like you can't expect delivery of anything in a normal manner any more, be it oil or a processor board.QuoteI'd love to see a modern take on the old Tektronix TM system of instruments. Possibly that instrument would be supplied with a built in computer running open source. A power supply being so basic should be a base component. However we get back to an issue you raised about cost. Going DIY and keeping costs at bay will not be easy.QuoteThere are all sorts of salvage available. However that creates a buildability problem if your goal is to create a design others can duplicate.

author: Swake
author_rank: Frequent Contributor
timestamp: February 18, 2022, 07:41:40 pm
content: What would be the modern equivalent of the lm723? and a power tor like the 2n3055 or the IRF440 mosfet?Preferably through hole or the 'bigger' SMD that can be hand soldered by most.

author: ledtester
author_rank: Super Contributor
timestamp: February 18, 2022, 07:46:45 pm
content: You might be interested in these designs which were posted to the forum several years ago:https://www.eevblog.com/forum/projects/diy-bench-power-supply-psl-3604/https://www.eevblog.com/forum/projects/diy-bench-power-supply-psl-24012/

author: jaycee
author_rank: Regular Contributor
timestamp: February 18, 2022, 10:20:59 pm
content: The problem is that such a bench power supply will require one of two things - a custom transformer with multiple secondary taps (plus separate taps for a floating supply for the opamps), or a switching pre-regulator. The latter is complicated to design, and the former almost certainly has to be a DIY job requiring experience in winding transformers. There is no way around either requirement.

author: rpiloverbd
author_rank: Regular Contributor
timestamp: February 19, 2022, 11:12:56 am
content: May be no open source... but I found vantek power supply good enough. Doing justice to the price.

author: Swake
author_rank: Frequent Contributor
timestamp: February 19, 2022, 09:07:18 pm
content: Thanks for the links to the PS created by Liv. These look very nicely build and I will check them out very soon in detail. I never wrote stm code, but that will probably not stop me.