Hey guys, another question regarding the optimization of motor voltage:
On my K8200 is there a riskless way of measuring motor driver voltage? I’m really afraid of producing short circuits with my probes because there is so little space around the via that is apparently supposed for voltage measuring… don’t want to zap my controller board…
Thanks a lot!
Alright, figured it out by myself.
If anyone needs to know: you can stick the GND probe into one of the end switch plugs to get ground. With a small all metal screw driver you can adjust the voltage by turning the trim. While you do that you can measure the voltage by holding the plus probe against the screw driver.
You should be able to measure the voltage there when you touch the trim with the “probed” screw driver. If not also check the GND probe! Doing this you can actually measure the voltage while adjusting it.
Pretty convenient.
Oh man! That’s a GOLDEN tip! Why is this not already common knowledge! How sure are you that the reading is 100% correct and uninfluenced by other components etc? (Not doubting you, just like facts 
)
…and, sorry - do you mean the motor amperage? I have trimpots to adjust the amperage, the voltage is constant (as I understand with my limited electronics knowledge!)
@Jarred_Baines I thought is was common knowledge that the “screw head” part of the trim pot (if it’s a metal one) is electrically connected to the wiper…
Re: stepper voltage vs. amperage, this is a bit of confusion that I’ve seen several places just recently.
The stepper driver controls the CURRENT (amperage) that goes to the stepper motor. Its a current limiting driver, and it limits current by providing the full supply voltage to the motor at a decreased duty cycle.
The voltage variable is a reference voltage somewhere between zero and the driver chips logic voltage, set by the trim pot, which is read as an analog value by the stepper driver chip, which uses it to determine its current limit for the stepper. The datasheet for each driver chip lists the equation it uses to convert reference voltage to current limit.
Its probably common electronics-person knowledge… I’m celebrating my first GOOD soldered joint this weekend, just for reference lol.
But I also have a reprappro Mendel, with melzi electronics, its plug and play and in reprappros documentation they show setting the trimpot differently, pointing out that its tricky to probe in the correct spot.
Also means I didn’t get stepper drivers, well, not ones with a data sheet - they’re integrated on the board and that’s as much as I know!
Yeah, maybe it is common knowledge for some privy folks, hehe. It however wasn’t for me.
I guess since the screw head of the trim pot is apparently directly connected to its wiper the voltage measured there should be pretty accurate. The screw driver I use has almost no measurable resistance. So, yes, I’m pretty sure the measured voltage is accurate.
Great! That’s a much easier method so thanks @Hendrik_Wiese