I just created a PCB like this one:
There's no capacitor plugged in right now, the holes on the PCB have been made for "backup-reasons" as i might need them someday (maybe now?).
Works fine testing with a battery at home, had this running for a few days. But it doesn't when I connect it to the frequency inverter which runs a Motor I want to watch over (The frequenzy inverter has an analog output on it, using an older version of this one here). In fact it works well for a couple of time but then the Raspberry Pi doesn't get any feedback from the MCP3208. The ADC is quite hot when it stops working. When I replug the cobbler it's working great again for some time - no need of restarting the Pi.
Just took a look on the analog output with an oscilloscope and it looks like this:
Isn't that stable, might that be the reason for my problem? There are two more motors near to the Raspberry Pi B+ and the connected PCB (AC motor). Some said it looks like these two would get the system stop working - don't know. I'm using a screened cable to connect the PCB to the frequenzcy inverter. The Raspberry Pi is getting Power from the USB-Port of the screen which get's it's power from the same socket as the motors and the frequency inverter does.
Can attach my Code too if you want too.
Already tried to change the Raspberry Pi including the microSD, changed the PCB including the MCP3208 and the cobbler - don't know what to do getting it running stable for a couple of hours.
Very thankful for your answers and sorry for my bad english - I'm a german student and I can't get help on german websites