Stepper driver problem

Hey everyone,

I'm having a problem with the stepper driver 1.2 circuit; whenever I plug in the 12V line into the stepper board it seems that the L297 heats up and nothing else happens. I'm using the exerciser code from the stepper motor wiki page to test it out, but it seems that the Stepper motor jerks for a split second and then stops.

To test my circuits, I'm using a benchtop power supply (a Tektronix 503A) putting out 12V and 5V with their grounds connected, a handheld DMM, and a Tektronix 502A DMM. I also have available a Tek 502 signal generator and a Tek 2445 oscilloscope.

I'm monitoring the current through the 5V line on a DMM, and I have a current limit knob on the 12V line. I've been using it to limit the current to the stepper boards - it seems that the current limit is always being tripped, even if the stepper motor is not connected, so I know something is not right.

I've unplugged the stepper and the Arduino inputs; there's no issues with the 5V line, it reads a constant 5.43 mA, probably just powering the LED. However, once I plug in the 12V line the L297 starts to heat up; after about ten seconds it reaches 130 degrees F and I remove the 12V for fear of destroying the chip.

Now, at first I figured that there was a faulty connection...but this has been happening to three circuits, one of which was built on a solderless breadboard.

One of the stepper circuits I built on a solderless breadboard, and it has the same issue.


We etched our own circuit boards, and spent hours checking the traces, then more hours soldering them together (on both sides of the PC, then more hours verifying the connections. My team has been meticulous with checking the boards for shorts or unwanted connections, and I've spent hours going over the breadboarded circuit. I found it strange that all three boards would have the same problem, even the breadboarded one. I started to wonder whether or not it was a design issue, but no one else seeems to have reported it, so I've discounted that.

Any help is appreciated; my team has been working on our Darwin for a month despite heavy courseloads, and we're very close to finishing...

I'm not an electronics expert, but I just put together my own stepper controller boards. While debugging one, I learned that the 12v powers the green LED and 5v powers the L297.

Try switching that around.

Yeah, that solves it...wow, so much effort because of misreading a schematic

Now the L298 gets hot, but I suppose that's normal.

Thanks a lot John!

Aaron Ramirez Wrote:
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> Now the L298 gets hot, but I suppose that's
> normal.

Yes. Put a big heat sink on it and cool it actively.

No problem Aaron. Glad to be able to help.

About the L298. As Joachim said, some people put on a bigger heat-sink. I've also seemed to notice that if I adjust the trimpot as low as I can possibly stand, it seems to help keep it cooler. I've also been thinking of aiming a fan at them.

Good luck,