March 3, 2014
I am attempting to drive a Karlsson 267 oz-in Stepper Motor using a Allen Bradley PLC to drive an automated book scanner system. The stepper is rated for 2.8A (I thought this meant 1.4A/phase, which made the BED an option). The PLC has 24V transistor outputs hooked to STEP, DIR, and GND. I used a voltage divider of R1 = 1.5M and R2 = 330k to yield V input = 4.34 V and I input = 16uA to meet the specs per the A4988 datasheet so I don’t see the PLC being the issue. M+ is hooked to a 24VDC power supply.
When I first ran the program, the BED was fine and the stepper was making sound but did not step. Per the directions in the user manual, my next step was to adjust the current pot. I used a multimeter to GND and TP1 to get reach a Vref = 1.76, to reach the max 2A. The stepper started to sound closer and closer to actually stepping as I turned the current up. During the process of adjusting the pot, the board turned off. I assumed it got too hot and the voltage regulator temporarily shut it down. Now every time I power up the board, I hear a quick pop, the LED go bright and depending how long it has been sitting, it dims out and board is off - this usually takes between 1-3 seconds after power up. The component nearest the motor pins gets very hot if I leave the power supply turned on to the board. The board quickly turns off regardless of where the pot is set.
Is this board fried or is it overheating? How do I correct this issue? Heatsink?
Is the board compatible with my stepper or do I need a different driver board? If I need something else, is the Probotix SideStep driver a compatible board for my application?
Any and all replies are gladly appreciated, I am very ready to solve my stepper woes.
EmbeddedMan PLEASE HELP.
Here is the link for my stepper:
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