Revive old power supply project or start from scratch

[Ford-Prefect]

Hi Folks,

I am new to this forum and came here since I recently watched eevblog on youtube over and over.
The reason for this thread is that I stumbled over the power supply series of Dave and that reminded me of an old small project that became something like an ugly sleeping beauty. I started with electronics some years ago when as a student I helped to set up an after school club for pupils to solder small circuits like blinking led stuff, buzzers, etching PCBs etc. Back than I had the idea that a bench power supply for at home would be nice. I had a rough plan and shopped some parts but then finishing studying became more important and in the end I forget pretty much about it and didn't do a lot in soldering for a long time. But now I am fixed on again and also want to dig deeper and start with micro controllers and stuff. So a power supply would be handy and this brings me right back to the topic.

The Idea back then was quite simple. It would have been a symmetrical power supply with different fixed voltages and an analog ampere meter for each channel.
I got two of these https://www.reichelt.de/schaltnetzteil-open-frame-5-24-v-1-5-a-sp-1500-p57778.html
and two similar to these https://www.luedeke-elektronic.de/Drehspuleninstrument-Amperemeter-0-1A-DC-No-60.html.
I planned to connect the ground of one to the positive rail of the other over a switch to select symmetrical output or seperated output and use some turning switch instead of the setting jumper.
Since it's output shouldn't exceed 1.5A I had planned to put some thermal fuses on the output.

So I could just do it right now but actually I think it's not really a good device. I assume a voltage and current regulated device would be more handy and a bit safer in case a test goes wrong. Also I don't know if I really need symmetrical output. I think it could be handy in case one plays around with opamps. But I  also heard that often ground is used instead of a negative voltage. When I saw the video series I thought maybe it could be a good Idea to just use one of this power supplies and set it to a fixed voltage and use it as an dc input for a voltage and current controlled power supply with digital display etc. so doing something similar as Daves supply but not with batteries and not with serial control etc. And maybe with higher voltages.

It's often said that this kind of stuff is a good entry project. However, although I could roughly follow Daves design I think I couldn't come up with something like this. So a design would be more or a less a combination of copying and varying solutions of others.

Does anybody have some advice for a novice where to start?

[tkamiya]

I don't know which video or Dave's supply you are talking about.  But if you want to do it right, power supply is a very deep and difficult subject.  Noise, ripple, temperature coefficient, transient, etc, etc, etc.

On the other hand, there are many easy kits available that mostly use 3 terminal regulators.  For many hobby projects, those will do just fine.

If you don't mind old and heavy, HP's variable power supply 0 - 40V 1.5A dual channel types are available for 20 dollars or so, if you can find them locally.  I have a stack of them but shipping would be prohibitive.  I don't know  how old is old, but is there something you need improvement?  Is this for fun?  Otherwise, usable ones are available cheap on Amazon.....

[Ford-Prefect]

Hi tkamiya,

I was referring to this project of Dave https://www.eevblog.com/projects/usupply/. Seems he stopped it at one point. Maybe that should make me thinking.

This is all for hobby and entertainment. I really like programming and technical stuff. It's always like some kind of riddle. This supply units I already have, I assume they are not bad and they are still sold too. But back then doing stuff for this after school project this was all 9V based analog circuit stuff. That made fun but thinking of some private projects for the future it's more about micro controllers and mixed signal. And there something in the 3V range, being regulated not in really coarse steps together with current limitation, might be more handy.

[nemail2]

Seems he stopped it at one point. Maybe that should make me thinking.

Dave is working on it, he mentioned in some of his last videos that the µSupply IS happening. He seems to have progressed quite far already.
He is doing it behind curtains because the last project went kinda wrong because everyone was suggesting and criticising things and he tried to implement everything and listen to everyone and so eventually it died of features I guess.
I guess the µSupply will be Daves "next huge product" after the µCurrent and the EEVBlog multimeter. I hope it will be open source.

In the meanwhile you are welcome to take a look at my supply which has been kind of inspired by Daves work:
https://github.com/mamama1/LabPSU_Darlington

I guess my project is too huge to simply rebuild it at home but maybe you can gather some ideas from it. In the end, that's what open source hardware is for.

[james_s]

Power supplies can be as simple or as complex as you like, you don't always need something fancy. For many years I relied on simple power supplies I built myself, many times I've just used surplus wall warts. Features like variable voltage and current limiting are nice to have but not absolutely necessary for many things.

[Enigma-man]

I agree with james_s.  You don't need to be fancy for what you want to do.  However, you may need something different for other types of projects.
There are many ready made ones that will do the job today and when your requirements change.  I don't think you would be wanting to go through the same process of looking for another  power supply to power your future interests.  You may be better off to buy one off ebay or elsewhere that has more than you need, but has the capability should you require it, unless your
goal is to have a collection of power supplies like some people who collect scopes, voltmeters, frequency counters, etc. (Which is okay) 
You have many options.

[Ford-Prefect]

Okay, maybe I will skip this topic, sell the few parts I already have on ebay, buy something on ebay or aliexpress, and spent time on other projects.

Maybe some old lab equipment if I can find or something like a DPS3005 or a Korad. It's not super convenient but will do it. It's not easy to keep it humble if one get's spoiled with nice equipment at work.

[ArthurDent]

Ford, I think we may have traveled together in the past. 

Personally I'd go with a commercially made dual supply like this one so I could experiment with the other stuff I'm interested in and not worry if the power supply is working the way I'd expect or whether it's the circuit causing a problem. Supplies like this with 4 analog meters let you see what is happening without having to switch between outputs. This one also has a fixed 5VDC/3A unmetered output which could be handy. These are linear, not switching, supplies and are heavy. Used they are generally in the $60-$100 range plus shipping. Here's an example of one on eBay. These are fairly common so they should be available used in Germany as well. Keep an eye out and you might find a good deal.

https://www.ebay.com/itm/GW-INSTEK-GPC-3020-Laboratory-DC-Power-Supply-Dual-Tracking-with-5V-3A-Fixed/264324890442

[Ford-Prefect]

Yep that were times, have you heard of Marvin? I hope he's fine .

Thanks for your Input. I think the hole story started with the frequent quote that power supplies are nice beginners projects. The Instek stuff seems to be really rare in Germany or even Europe. I found something similar, but it looks like the mains are openly connected on the back, since it's designed for a rack. https://www.ebay.de/itm/Lambda-Messgerat-3fach-Mesgerat-Netzgerat-Modell-LPT-7202-FM/173913711378?hash=item287e10a312:g:~5UAAOSw~TdcxGx4
Maybe one could create some housing for this to make it child proof, but I don't know. I will have an open eye.

[james_s]

I've often said that power supplies are nice beginners projects but when I say that I mean simple power supplies, the sort of stuff I was making when I was 12-18 out of mostly salvaged bits. Transformer, rectifier, filter, 3 terminal regulator(s), that sort of thing. I got by for a long time on this sort of thing and building a power supply like that touches on a lot of fundamentals without anything being all that critical. These days I suppose it's easier to suggest just buying a decent bench power supply from the start but when I was starting out a proper bench PSU was a substantial expense. There was no ebay or inexpensive Chinese brands.

[Ford-Prefect]

Ok, I think I got it.