Matrix user forums

Ok, not really an explosion, but there was some smoke...

I was driving a DC motor (too powerful) with PWM on 2 different EB011 boards for testing reasons, after switching direction a couple of times repeatedly, the L293D chip which was driving with PWM started to smoke and pretty much died. I knew the motor was too powerful, I wanted to test the protective circuituiry, which failed to protect the L293D.

My question is, why didnt the fuse protect the L293D?
And what are my options?

Dear regards

Hello,

The resettable fuses will prevent a prolonged over current but are not great at stopping quick over current spikes like you get when changing current direction on a DC motor or other inductive coil.

You could use instead the EB022 motor control E-block which comes complete with protection diodes or you could replace the L293D chip on your EB011 and add some protection resistors to limit the inrush current. Say 5 - 10 ohms in series using a watty resistor should do the job and help to protect the IC. A further measure would be to add protection diodes but if you are already limiting the inrush current then you may get away without needing these.

Hi Benj,

Thanks for the response, would it also be possible to replace the L293D with a L293NE? This one seems to be able to supply more current then the L293D.

Greetings.

edit: after some more research I found out that the L293D already has diodes to protect the outputs, so now I don't understand how the IC could have died. As the high current spikes should have been carried away by the diodes, am I right?

Hello,

The chip does have some protection but I think the chip probably expects a heatsink or other form of heat venting to allow it to run without damaging itself under high load. Also internal diodes may do a bit to protect the IC but they are probably not high currect enough to fully protect the IC from very large surges or spikes.

Not looked into the L293NE device but if it is pin and voltage range compatible then you should be fine.