I have a project with a few custom PCB driver boards driving 6 stepper motors each. The PCBs use both 12v and 3v. The screw terminals for the in/out power are rated at 10 amps and with each PCB pulling roughly 1.5-2 amps at peak (majority of this being 12v) I am daisy chaining 4 at most with the 12v power.
The 3v which comes from a buck converter powered via the 12v power supply should be able to daisy chain to all PCBs without causing any issues. However, im unsure what to do with the buck converters ground out. Do i just bring it back to the power supply? The screw terminals i have all are are a single in/out for 3v, ground, 12v so i wouldn't have another spot for the 3v ground wire to be installed.
Or should I possibly splice the 3v outgoing buck converter ground into 3 different 12v ground wires?
Picture for reference on what I'm guessing I could do?
Every buck converter I've got has a direct in-out path for the - side. But, I have to admit that's a pretty special unit, I usually limit my purchases to <$2, and it hasn't bit me yet.
Meaning if i check with a multimeter for 0 resistance it should have direct ground to ground connection. So if each of the PCBs have ground out directly to the 12v power supply it would equal out all in the end?
That's correct, sort of. Think about current paths. Normally, you don't want return currents from large loads to run via the same wires as your logic ground. We usually recommend a "star" ground. In your case, I'd fan out both + and - from the power supply to each strip and to the buck. That moves large current induced voltages away from the DCC voltage. (that may be what you're showing in your diagram).
Checked with a multi meter. Ground in/out of the buck converter looks direct as theirs essentially 0 resistance. Could you explain what you mean by fanning out the +/- to each driver board tree and the buck? I guess I'm not understanding
I threw this together really quickly for a visual. Ignore all dangerous exposed wire or unorganization this is just for a look on what i would be doing here. If needed i can try to organize a bit more with something like yarn or string to make it a bit more visual/organized
Here's how I'd do it.
Feed PS voltage in the 2-connection side. Out to the LED strips and the buck converter. These are available in 2-4, 2-6, and 2-8 versions. Neat, organized.
These things are all over my model railway.
I guess the issue I'm thinking is each PCB board only as a single screw terminal for ground in/out and if im daisy chaining i only have a single option to bring ground back to the source. The above looks like its still split into 3.3v and 12v ground no?
Unfortunately, you're faced with a design limitation. All you can do is work with what you've got. The large currents will have to share wire with your logic, for better or worse.
