I am trying to control mechanism involving a nema 17 stepper motor. I use an A4988 stepper driver and an Arduino Nano both powered by the same 12 V/3A power supply. So far I have fried or crippled 4 Arduinos along with an A4988 or two. I have tried to sketch the connections. The potentiometer tracks the position of the mechanism that is actuated by the stepper motor.
Initially I suspected my poorly soldered wiring (probably partially rightfully) but I have since done the wiring using prototype PCBs and checked for short circuiting quite thoroughly - and this set-up actually worked for some minutes and then stopped. It is some while ago so I am not exactly sure, but I believe that at the time of the latest failure, the connection between the potentiometer and motor snapped resulting in quick motion of the potentiometer by a spring.
Some of the Arduinos are completely bricked but the last one seems to work, only the 5V pin outputs 4V indicating that the voltage regulator is damaged. Before I keep on frying Arduinos I hope someone more experienced could offer some pointers. These are the things I have suspected:
- the arduino, the A4988 and a slide potentiometer are all connected to the same ground. Could the motor induce a current back through ground that could fry the Arduino?
- the potentiometer is 1kOhm and as far as I can tell this should be a bit low but ok currentwise. I have bought a 1 MOhm potentiometer to replace it but have not powered the circuit yet.
- I assume that the potentiometer cannot induce any current even if it is moved quickly?
- I have seen several examples where a capacitor is connected between 12V and ground and intend to add this. Could that somehow explain the faulty behaviour?
- Is it a problem to power the motor and the Arduino from the same power source (which should be able to supply the required current)? Implicitly the power source also powers the A4988 logic voltage via the Arduino voltage regulator
- I have checked the circuit for short circuits quite thoroughly while powered off, but am I correct to assume that powered on the circuits wont expand and create shorts?
- anything else?
Eventually I will try the greater resistance and the capacitor but I hope with your help to spare any unnecessary Arduino casualties and get a generally robust result. Any help is much appreciated - thanks in advance