Hi everyone!
I am very new to modular synth diy, my first project (after building a small drone) is a power supply for a larger case. But I am really bad at schematics and don’t have access to buy the frequency central power supply diy kit.
So I thought I would build my own on stripboard and found this video made by Moritz Klein DIY SYNTH PSU: How to design a simple dual power supply - YouTube of how to build one but unfortunately he doesn’t share a strip board layout.
Is there anyone that would be able to help me convert his schematic into a strip board layout, or maybe give me some tips on how to do so?
Can you read a schematic? As in, you know what all the symbols refer to and how they’re connected together?
If so, most people use diyLC to layout stripboards. That might be a good place to start.
This would be an easy layout, as it would almost be literally as seen on the schematic. That being said, you’d need to google the pin out of the 7812 and 7912, so that you have those oriented the right way and you’ve connected the input to the input, etc.
Something else to note is that 4700uf capacitors are quite physically large - you’ll want to find the dimensions of the ones you’d be buying. You can change the size of the components on diyLC to match.
If you can’t read schematics, that would be the place to start.
Ahh thanks for the tips!
I know what the stuff means, especially in this easier schematic, although I have a rough time converting it to a strip board layout… I will look in to diyLC!
thank you!
By the way, in @THOGRE’s design I recommend changing D8 (from +12 V to ground) from a 1N4004 to a 1N5817 or similar Schottky; see posts starting here. D4 (-12 V to ground) can stay a 1N4004, or I think probably can be left out entirely as talked about later in that thread.
Hi again!
So I managed to design a strip board layout that I think corresponds with the schematics, but after staring at it for so long I can’t find my mistakes anymore… So I would be really thankful if someone would be able to point anything wrong out.
Another question I also came up with is if it would be able to use 16 v capacitors for the 4700uf ones? I accidentally order those instead of 25 v ones…
Is there some reason you’re not just using @thogre’s design (maybe with that diode swap I mentioned)?
You should have 1N4004 diodes between the regulator outputs and inputs.
Added: Oh, I see, you’re using the schematic above. I’m not sure I like it. My understanding is both regulators should have 1N4004 diodes between the output and input, not just the LM7812. (The one on the LM7912 would point the opposite direction.)
In addition, as I mentioned earlier, I get the impression the diode from the LM7912 output to ground seen in many designs, like MFOS and LC, doesn’t really do anything useful and can be omitted, but a 1N5817 or other Schottky, not a 1N4004, from the LM7812 output to ground fixes a potential startup problem.
Different designs use different amounts of capacitance before the regulators, e.g. 4x4700µF or 6x3300µF vs 6x4700µF, and my understanding is it’s not a simple case of “more is better” — the FC designs do use 6x4700µF, but I’ve seen that criticized. It’s probably OK either way.
My suggestion is to start with @thogre’s design, maybe add two more 4700uF if you want, change the one diode to a Schottky, maybe leave out the corresponding one on the LM7912 side, and go with that.
You can always add those diodes later. The output to input one is to protect the regulator in the event the input is shorted, and with any luck you won’t have that happen before you get around to adding it. The Schottky prevents a startup problem you might not have, or if you do there’s a workaround (turn it off and turn it back on again right away).
Added: Oh wait:
With negative regulators and the LM117, there is an internal diode in parallel with D1 from output-to-input, eliminating the need for an external diode if the output capacitor is less than 25 μF.
But with multiple modules connected, isn’t the total capacitance well over 25 µF? Anyway, that diode would do no harm, I think. I’d still add it.
Ah ok, yes Moritz mentioned the internal diode in the video, I’m just starting off with a few modules sothat shouldn’t be a problem? I am gong to order the extra diodes with my next order of parts though.
what are your thoughts on the 16v capacitors will they be enough or do I need to order 25v ones?
Oh no, 16 V isn’t enough. 12 VAC is RMS and the peaks are around 17 V, and before the regulator the DC voltage will be in the 15–16 V neighborhood. Caps rated for 16 V might work if the rating’s conservative but they’d be on the edge. Use at least 25 V or 35 V ones.
Hi @VincentEklund ! Welcome to our forum. I hope you will find us as helpful and welcoming as you could wish. I’m so glad somebody helped you to get started.
For the sake of symmetry, wouldn’t you want to add a protective diode (arrow of diode pointing from the input to the output) across the LM7912 as you did on the LM7812?
See above, negative regulators have a built in diode the positive regulators lack. But it’s only good up to about 25 µF output capacitance, so I think if there’s more than a couple modules connected you would indeed want to add the external diode.
Just to comment…Power Supplies are usually the most uninteresting part of any build… but absoloutely essential if you are going to build anything else!
Thay also tend to be fairly straightforward, and as long as care is taken regarding mains voltages, are a good way for a begiinner to start any build.
I would recommend building a PSU (power supply uniit) as a starting point for anyone starting in synth DIY.
One tip: sprinkle your power supply lines like confetti with 100n capacitors (film or ceramic) between the output power lines and grounds. Anywhere!. Everywhere!
It’s called ‘decouplng’ and is good practice to have a such capacitors in all your circuits. It reduces noise and interference from the power supply and other circuits, and false triggering of modules, etc.
100n capacitors cost pennies. I buy them by the hundred. Use one on your power line wherever there is spare space on a circuit board.
Without going into the engineering theory, it is desirable to have a power supply that is as free fron noise and interference as reasonably possible, especially in a audio system that uses voltage control such as an analogue synth.
Think of these 100n capacitors as ‘little batteries’ that cope with local spikes in current demand when a circuit switches or changes, wiithout drawing spikes in current from everywhere else in the system.
Yes pointing the opposite way as that is the negative side of the supply.
These diodes are there in case, when the power suppies are turned off (or inputs to the regulator shorted), the capacitors connected to the output side hold a higher voltage charge than the discharged capacitors on the input side.
When that happens, there could be stored voltage at the output that is higher than the input voltage to the regulator. Result - damaged regulator.
The diode limits this voltage difference to about 0.7v, which is unlikely to cause damage to the regulator.
A 1N4004 diode costs about 2p, so fitting one is a ‘no brainer’.
A 1N4005, 1N4006, 1N4007 will also do fine, the difference between these diodes is the voltages they will tolerate.
