[probably solved] Lower Voltage from pins, when Arduino is connected to circuit.

[CaptainTimberTim]

Hello,

i try to use the Genuino MRK1000 as a controller of 12 MOSFETs (RFP12N10L) to control peltier elements with the PWM pins, which are connected to the source of the MOSFETs with an external power source. The schematic shows the setup of the circuit. 


The problem is, that when I connect the Genuino to the circuit it outputs a lower voltage the more pins I activate. Not connected to the circuit it always outputs the full 3.3V. I narrowed the problem down a bit, with leaving the peltier elements and the extra power source out.
I am really no expert in electrical engineering, so I'm assuming it might be a problem with the circuit setup itself, but Im not sure. I'd really appreciate help, thank you in advance!


-> PROBABLY SOLVED!
After a bit trial and error testing I think I found the solution to my problem. The 10k resistor was too small. I changed it to a 470k resistor and am now getting the full 3.3V on every pin, regardless of how many are active at the same time.

[pwillard]

Very Likely the reason... each pulldown became a load that would increase the current draw each time on was activated.

[Grumpy_Mike]

The 10k resistor was too small.

Very Likely the reason... each pulldown became a load that would increase the current draw each time on was activated.

But the load of 6 resistors at 10K with 3v3 is only 1.98mA, what sort of crap processor can not supply 1.98mA over 6 pins? Not even the Intel processor in those things is that bad. There must have been something else wrong. You sure you set those pins to be outputs?

[CaptainTimberTim]

yes the pins are definitely outputs. That could'nt have been the problem. But for the time being it is working. I shall write if something unexpected happenens or we find the real solution/original problem.
And I'm always interested in other approaches to solving the problem.

[Grumpy_Mike]

And I'm always interested in other approaches to solving the problem.

The approach of waiting for it to magically start working by itself will not always work.

In this case it sounds like you have loose connections caused by poor / no soldering.