I was having trouble driving a Progressive Automations Micro Linear Actuator, part number PA-07-2-5 with PWM.
It’s much simpler than I expected. Some circuitry, a small gearbox, and the piston, which is just an Acetal or UHMW bushing around a lead screw.
Turns out that this thing isn’t just a couple limit switches and a motor, like they describe in their datasheet. There’s actually an overcurrent protection circuit, which trips when the actuator hits the limits and shuts down the circuit until power is turned off.
You can see this above:
- power supply on, the actuator starts moving after a brief current spike.
- there’s another current spike as the motor stalls, and this trips the overcurrent protection, which turns off the actuator.
- power supply off, and the PSU capacitors discharge
- you can see another current spike the voltage on the latching transistor drops below the threshold, and the current enters the motor briefly again
- power supply on, immediate stall, overcurrent protection trips again