DIYEFI.org Forum

That's interesting. I has considered feeding our ADC ref with the secondary supply for the sensors too. You have to be very sure it is very close to the voltage seen on the supply pins though, apparently only a little variation can damage it.

The wavery power supply lines could have detrimental effects on other aspects of the CPU operation too. Did you consider trying to smooth the main 5v line more?

Fred.

No the transients were too fast (and too small) to affect any normal operation of the logic components. But even a 0.01v transient showed up on the ADC readings - as it should ......
I didnt look at the schematics in detail yet - but i think the transients may be due to the power transistors like FETs and IGBTs since the power ground does not seem to be separate from digital ground. I tried a whole lot of capacitors on the 5v rail - didnt help that much.

Both power and ground are separate to the connector and joined from there to the source. However the idle transistor is grounded to the digital ground, so if you do PWM idle with an upgraded transistor you can easily get noise inside.