Easydriver troubleshooting

I recently blew up my easydriver by connecting 5 wire unipolar as bipolar without limiting the current. I literally saw the chip pop in the middle with little spark and the chip surface has a big bump - lesson learned.

Now, a second easydriver seems to be malfunctioning - the 5v light comes on but it does not energize the motors. I checked against another easydriver and it is definitely nothing else (motors, wiring, etc.). Is there a common issue to troubleshoot or shall I just trash it?

I didn't think you could run a 5-wire unipolar motor with an EasyDriver.

Have you a link to the Easydriver instructions for how to connect it?

And then draw a diagram of how yours is wired and post a photo of the drawing.

...R

Hi. You can ran many unipolar motors as bipolars - would have to separate the center-taps for that. also, this was a hybrid motor and they are known to draw the current like crazy. This was a reason why it blew up my driver. You can search the web for more info.

Regarding the current situation - I have been using the Easydriver and understand how it works. As I mentioned in the previous post, I checked it against another easydriver to make sure the wiring was not a problem. My question was if there was a common easy-to-fix issue that the community was familiar with - otherwise it would be waste of time to try to fix it. Basically, the 5 V light comes on but no output in leads to energize the stepper.

mvoltin:
Hi. You can ran many unipolar motors as bipolars - would have to separate the center-taps for that.

I am well aware of that, but you said you were using a 5 wire unipolar stepper and you said nothing about having converted it to a bipolar stepper.

I don’t think you will get much help until you show a diagram of exactly how everything is actually wired - including your power supply.

…R

5 wire motors have the two windings connected at the centre-taps and cannot be
used with bipolar chopper drives (as you have discovered). The two phase windings
must be separate for bipolar chopper drive, so 4, 6 or 8 wire motors are OK.

It is in theory possible to use H-bridges to drive a 5-wire motor, but only with the right
decay-mode (and great care), so in practice 5 wire motors are unipolar only.

I would have thought the failure mode would be misfunction rather than blowing
up the chip though - you must have been running it close to the thermal limit already...

Hi Mark,
I actually just turned it and started spinning for 3 seconds. then I applied resistance (by hand to check the torque) and the chip blew up within 3-4 seconds. This was also a hybrid motor and I read somewhere that these things draw tons of current. I think not having current limited got me into this.

Anyway, this was a side note. My actual question was about another Easydriver that stopped working for no apparent reason. Was wondering if there was a way to troubleshoot (easily enough to make it worthwhile).

Again, the 5 V light comes on but does not energize the coils. It is definitely not connections or wiring because replacing it with another Easydriver fixes the issue (went back and forth few times).

mvoltin:
Was wondering if there was a way to troubleshoot (easily enough to make it worthwhile).

I'm not sure how to do that without a bipolar motor that you know works properly with it. Maybe you could wire some resistors in place of the motor coils and look at the voltage across them using an Oscilloscope.

No, chopper drives only work with inductive loads.

MarkT:
No, chopper drives only work with inductive loads.

So what would be likely to happen if I put a couple of low resistance high watt resistors in place of the motor?

...R

Buy some spare chips and try it?!

Why though, it certainly won't work as a chopper, which is basically a
a pair of programmed constant-current buck-converters using a motor windings
as inductor and load.

MarkT:
Why though, it certainly won't work as a chopper, which is basically a
a pair of programmed constant-current buck-converters using a motor windings
as inductor and load.

I'm just feeling my way with this stuff.

I assumed that if I put a couple of resistors in place of the motor coils I could put an oscilloscope across the resistors and see whether step pulses are being generated by the driver?

Would that happen?
Or would nothing happen because the driver would realize there is no inductance?
Or would an uncontrolled and therefore damaging current flow?

I have the impression from reading the Allegro A4988 datasheet that it only indirectly takes account of inductance as all it seem to do is measure and limit the current.

...R