Hi everyone. I seem to be having some issues outputting the correct voltage on the Frequency Central PCB. I’m outputting ~26V at the +12V point and ~10V at the the +5V point. The negative -12V point outputs 0 voltage. I also have another of the exact same PCB - same issue. If for any reason you know what could be the issue, I would appreciate your help. Thanks!
Is your wall wart AC-AC?
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hi & welcome, i don’t really know if it’s very important but it seems that’s not the good size leds (should be 3mm).
have you not invert 7815 & 7915
check the polarity caps + = square / led + = circle
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You are using the wrong mode for your multimeter!
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Thanks, yeah I had 5mm LEDs instead of the 3mm LEDs, but I figure that shouldn’t be an issue? Also, I checked polarity and it seems to all be good.
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Oh boy, I must be dumb - what’s the fix?
Change to this setting. Where you are testing it, it is no longer AC, but bipolar DC.
You aint dumb. Hell i did this not even an hour ago so thats why its fresh in my head.
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Thank you so much! Everything works out now. Check your multimeter kids
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While we are here, i actually have some questions about power supply setups. I was actually going to make a post about this before this thread popped up, but i guess this is as good as anything.
I have a FC microbus and some power bus headers (the ones @analogoutput made). My setup is getting a bit larger now, and am running out of headers. I have had some lingering questions about the process of scaling the power supply.
1: Is it ok to just use one header from the powersupply to supply the passive bus with everything?
2: At what point do you need additional walwarts? That seems like a pain to have one for every row, and doesnt sound right.
3: Do people mount these passive busses with standoff pins or just screw them directly in. If the bottom of the headers contact with wood etc. Sounds bad, but I believe i have seem people do it. Am i worrying too much?
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dam I didn’t even notice that , good eye there detective Caustic .
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As long as the traces on the power supply are heavy enough to handle the current you’re pulling you should be fine. (i.e. that’s how I’ve done mine)
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I have one per case. It’s hard to say since different modules pull different amounts of current. And I keep getting confused about just how much current an AC walwart can provide. You could measure the draw of your modules to figure it out…but one per case seems fairly safe. That’s assuming a two row case and one power supply per case (since the regulators on the power supply have a lower current limit than the wall wart.)
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I 3D printed some standoffs for mine. I also went a little overboard and used brass inserts in the wood for the screws to screw into - but since I doubt I’ll ever pull the buss boards out it’s serious overkill.
I also used connector terminals so it’s easier to plug unplug things, (with crimped ferules on the wires where they go into the screw terminals) and made a 3D printed plug for the case where the power goes which I brought the power LED’s out to so I can see that both power supplies have both voltage busses working as expected even when they’re hidden behind modules:
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Wood’s nonconductive. There’s no need for standoffs. And using standoffs, I’d worry about flexing the PCB.
Are you talking about connecting an AO bus to a Microbus supply? That’ll be something like 20 headers between the two of them. If you’re using a header to connect to a header then that’s 18 headers available for modules — which might be pushing how many modules the supply can power. Depends on the modules. A dozen modules per supply is probably fine, 15 maybe, 18… check their current demands and verify they add up to under an amp or so per rail.
You mean one per row?
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Wood is non-conductive…but flexing of the PCB is actually why I opted to use standoffs. Without them the soldered leads will hit the wood first and the screws will have to be left loose or at least have gaps between the board and the case where the screws are. So I was concerned that without standoffs the boards would either be loose or flex. With standoffs I’m able to mount them solidly.
Though I do admit one or two of my holes were slightly off making a few spots where there is some stress on the boards. But drilling or reaming out the holes a tiny bit larger took care of that.
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Nothing wrong with loose. As long as the board’s not actually falling off, it’s okay, better than if it’s screwed down too tight, and without standoffs most of the insertion force goes to the pins and from there to the surface the bus is mounted to. With standoffs the insertion force is transferred to the PCB. If there are lots of standoffs the PCB won’t flex much but with only four or six standoffs I’d worry. And eight’s too much work.
Or if you’re really worried someone here, forgot who, made buses with SMD sockets so the bottom surface is flush. In principle that’s better but in practice I doubt it matters, as long as you use either zero or >=8 standoffs and don’t overtighten.
My latest bus board is, at least for now, held in place on a horizontal surface with zip ties. Not a problem.
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Yeah, the risk of flex when plugging un-plugging worried me a bit - And is why I used 6 screws and was worried I’d have to do more. But it’s really solid with just 6 and I can easily plug/unplug without any noticeable flex in the board since it’s mounted nice and solid. So I’m happy with it.
Honestly either way is probably fine here - just on this case I was putting in the extra effort on little things so I choose to go with standoffs and nice solid mounting…and I’m really glad I did because it’s so much nicer plugging and un-plugging power cords compared to my first case where the buss boards are loose. Just feels “more right” 
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Cool, sounds like im just going to need to get another power supply and walwart to scale up then. I knew that there isnt an easy answer for the power draw unless i myself measure the amps, but i was wondering if i was just being dumb thinking i would need like around three large walwarts to power my modules. Curious how people setup a switched power as well.
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When ordering my microbus, I contacted FC over Facebook, they’re very reactive and very helpful, so I’d say: don’t hesitate to contact them.
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Hello I hope I pick the right thread for this Problem.
Idk whats wrong with my PSU
I hope someone can help me with this problem
Thanks for your effort
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