My question is about powering a stepper motor, and what type of inductive quickback a stepper could generate and if this could interfere with the power supply.
I have purchased big stepper motors – so I can build something else later with them. They are 3.78V 4.2A 85 N*m with specs here: http://www.motioncontrolproducts.co....products_id=11
I am trying to power these using an ATX 300W power supply, using either the 3.3V or the 5V supply – both can deliver 20Amps. The ATX is working correctly, but every time the motor takes a step, the ATX is shutting down.
I tried the following things:
-Connecting one phase of the stepper to the 3.3V or the 5V output does not stop the ATX, so it’s not shutting down as a response to a high current surge by shutting down
-Shorting (briefly!) the 3.3V or the 5V to ground: this does not switches off the ATX – the fan just spins faster.
This means the ATX is not powered off by a short or a surge. I tried to add a capacitor (1000uF) across the 3.3V supply to see if I could suppress any spike – no change. Someone told me it could be a "ground bounce". This is where your ground (or return) wire from the GND on the controller to the GND on your power supply is not low enough resistance.* This can cause a higher voltage at the ATX supply end causing it to shutdown.
I tried using much thicker wire to connect the ATX to the controller, but this did not work either… tried using more ground wires from the ATX to the stepper bee+ ground (7 for them!) but no changes – the stepper takes one step and the ATX shuts down…
-what is the inductive quickback from a stepper motor? Could this be the issue? On the other hand ATXs should be powering the steppers (albeit smaller ones) running the hard disk… so there must be a way.
I could use the following things (or a combination of these)
-some diodes to block a negative spike due to inductive quickback. Will need the diodes to pass 4.2Amps and dissipate 4.2x1.5Voltage drop = 6.3 Watts. Will have to use the 5V supply because of the voltage drop across the diode…
-a giant smoothing cap across ground and 3.3V supply….
-a 3.3 Zener to bypass any positive spike due to inductive quickback
-A LC filter
-A MOV
… any ideas welcome!!
I’d be really grateful for your insight on this – how do you power your steppers suing a cheap PSU?
many thanks - Thomas