stepper motor needing a transient voltage suppressor

Zap-o

Hello,

devices...

A3967 micro-stepping driver from spark fun.
6 foot shielded cable for connection between driver and motor
Bipolar stepper motor
24 Volts DC power supply

data sheet...

http://www.sparkfun.com/datasheets/Robotics/EasyDriver_v43.pdf

problem...

The problem I am having is that the ICs keep blowing up when I remove the cable between the board and the stepper motor.

what steps I have taken to try to solve problem...

I called Allegro and spoke to a tech. He mentioned that the ICs can not be hot swapped due to the inductive load and I would need to install a TVS diode of some sort.

This leaves me uncertain as I am not sure where to place the TVS (transient voltage suppressor). If I need to place it between V+ and gnd or between the 4 wires that run the stepper motor and gnd. I measured the voltages on the 4 wires and as expected they run at very low voltages, since its almost a short. Current was around 100ma. This leads me to think that the 4 wires are not the place to put the TVS. This contradicts the Allegro techs idea that the coils in the stepper motor are discharging the inductive load into the A3967 h-bridge.

Any ideas?

Leon

I'd just avoid removing cables with the power on.

Zap-o

I wish that was the case Leon. The customer wants to be able to remove the cable.

Leon

Why on earth does he want to do that? Connecting and disconnecting things with the power on isn't a good idea, generally.

Zap-o

Leon,

So True. The cables are not supposed to be disconnected and connected while powered, but it could happen at times. This is why I need to install a TVS but where is the question?

Leon

I've only used them across the regulated supply for MCUs that might be affected by transients. I'd be inclined to try them across the stepper motor coil connections. Try them in pairs with the centre tap connected to ground.