Maybe, but be aware most wall warts have little or no regulation, so if you want a reliable 12.0 volts look elsewhere.
Many circuits will work OK a few volts up or down but it varies.
1 Like
Simple PSUs are the MFOS’ simple one operating from a 9VAC wall wart. Guess it’s the same kind Soundtronics use (in the MIDI Ultimate.
I will eventually order a SMPS module from China, but fear I will get tons of spikes and shlt: Dual smps module from Chian.
I use an ATX power supply I pulled out of an old desktop PC. I’ve got a breakout board from Amazon that gives me proper terminals to connect to (though the binding posts it came with weren’t ACTUAL binding posts, ie you couldn’t clip/insert anything to connect).
It works well enough–it’s got ±12v, 5v, 3v3 and ground, and the breakout board is fused, so that’s cool. The +12v rail only manages about 11.85v but I figure it’s good enough for government work.
1 Like
I use this for all my diy stuff. Just wire the negative lead of #1 to the positive lead of #2 and the junction of the pair becomes ground. The positive lead from #1 is +12 and the negative lead of #2 is -12. I put like ten or twelve modules for ever pair like the ones in your pic. Any more than that and you get some negative results. it all depends on how much current each module needs to function properly. I usually discover this if random modules start to act strange after plugging a new one in. At this point I just wire up a new pair of walwarts just like yours and it has worked like this for about 8 months and I’m still adding on. I’ve got 3 pairs filled up and working on my fourth, and as I’ve said I notice the need for a new chain at ten or twelve modules each ( i have twelve on one, ten on another, twelve one another and the fourth…) Keep in mind what @analogoutput has to say, because I do have some strange results to account for in my recent but eventful diy journey, although they happen with my regulated bench supply when testing as well as in the rack.
1 Like
Thx for the advice (thx @analogoutput too). I was thinking in wiring the thing in another way, but read your reply and checked a lil schematic and my thoughts didn’t make sense anymore lol, but yeah your wiring should work.
Also, yeah I kinda doubt it is a reliable PSU, but i’m thinking for a quick solution and I’m not planning on running a lot of modules on it (it’s not like I have any anyways). I might try the ATX thing if I find a PC power suply lying around.
1 Like
Just be warned old ATX supplies can have some bad ripple, maybe things have improved on newer generation PSU’s
1 Like
Oh, fair point. I haven’t looked at the power output on a scope, only on a multimeter. I’ll look into that. Thanks!
Is the power supplies are noisy, You could add LC filters to clean up the power rails.
If like me you have a few old laptop psus lying around, another possibility Im planning to try is to use two old laptop power supplies, connect them in series with ground connection in the middle add +12V and -12V linear regulators.
Most laptop psu’s output 18-19V at over 3 amps.
So, for all my big talk about my old ATX power supply being a solid, serviceable option, I’ve found that it’s nowhere near providing ±12V reliably. I saw it passing 10.5-11V on both trails the other day. So, I’m looking at my options.
Obviously, a commercial supply from a reputable manufacturer would be ideal, but, also obviously, those PSUs can be stupid-expensive. The cheap ones are, well, cheap, and you need two to get a bipolar supply. So, in the heart tradition of the electronics hobbyist, I’m looking at building something myself.
Looking at one option, I find myself looking at these self-contained buck converter units on Amazon (DPS3005/5005). I figure I can get two of them, filter the rails to clean up the ripple from the switching supply, and knock things together to give me a switchable bipolar/independent dual supply. So, does anyone have any experience with these things?
Two of those would be $78. You still need to supply voltage to them — maybe your ATX supply? Then there’s the filtering, housing, and so on. Not sure what kind of documentation they supply but from the Amazon listing I would not be optimistic.
Granted I may have gotten stupid lucky buying my 3x bench supply for $60 (used), but for your $100-ish I’d think you could find a decent dual supply or pair of singles and not have to mess around with wall voltages etc.
The other option is to build from scratch. I built a 5v linear supply for a project in university, so i know I can, it’s just do I want to actually do it. It’d be even easier with a 32VAC wall wart. I just dunno if I’m prepared to drop an entire $100 on this right now. Or if my wife is ready for me to, more accurately. I’ll keep my eyes peeled for surplus supplies and work on a design in the meantime.
I carried out load tests on two random* 12VDC wallwarts and was pleasently surprised to find that their regulation was pretty good across their respective current ranges.
Being switch mode, as most of them are now, they do have quite a bit of high frequency ripple, but this could be easily cleaned up with LC lowpass filters.
- by random I mean from the selection I have collected from various items no longer in use.
32VAC Wallwart might not be the best option, assuming that you are speaking of the type that powers decorative lighting, they tend to have pretty low cirrent available.
The other issue is with the rectified and smoothed DC output. Assuming youd be intending to use the typical voltage doubler type of circuit to get split rails. It would output around +/- 45V, meaning you need to lose 33 volts across each voltage regulator.
A 12-15VAC one rated at a couple of amps would be a better option.
1 Like
I think I had a variable supply in my head when I posted that, so I was thinking about a ±32V range with some overhead. That’s probably excessive, but those are the numbers I had in my head.
I still use this power supply I built at University 20+ years ago. Back when I still thought I was going to be an electrical engineer…
It is very simple and I like it.
4 Likes
Aw. I have a “20 years ago at university back when I thought I was going to be an electrical engineer” story too. HIGHFIVE
1 Like