I am using an Arduino Uno to control stepper motors which are 3.5 amps (pretty big ones, nema 34). I am sending the step and direction signals to a Gecko stepper drive, then the stepper drive actually drives the stepper motor.
I have done this in other applications and all has worked well, but those were AC powered with conversion to DC. With all the capacitors and such, the in-rush current isn't a problem.
However, this is a robot I am building and it is powered by 24V battery. So the only way for me to control power is a switch to turn it on and off for the stepper drive. GeckoDrive is suggesting the large in-rush current can damage the driver.
They have suggested using a current limiting thermistor to minimize the risk of damage.
Unfortunately, I know very little about electronics, nothing about thermistors of this type, and certainly don't want to damage the stepper drivers (about $80.00 each).
I am hoping someone here can help this old dog out and explain to me what size I need and how to wire it into the circuit.
You could use a two-phase turn on - first connect something like a 10 ohm power resistor, then after a second
or so directly connect - that allows capacitors to charge up at a sensible current. You could just have
two switches and manually sequence. Ideally you'd have a little circuit sequence things via a contactor or
relay.
The thermistor as an inrush current limiter is good. Initially, it starts at a higher resistance (e.g. 40 Ohm) and then as it heats up the resistance will dorp (e.g. 0.3 Ohm at 4A) and that will reduce its own voltage dorp. You need one that can handle the steady state current that will flow, I'm going to guess something like this: