March 2008

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I’ve been struggle (I mean fighting against the whole universe’s darkness) for three month trying to drive DC motors with a PIC 16F88. I know it would be tough, but I didn’t know it would be so hard… Because this is about driving high currents (from ~500mA to 1A), and not just logic states as before. This SirBot ticket is a nice summary of what I’ve faced.

Of course, there’s a lot of people doing this, but it appears experience cannot be shared as easily as for other projects. I mean it seems that there’s a lot with the environment. Starting with the motor itself, which could definitively pertub the power supply, thus the PIC itself. Or the chip used to drive the DC motors: using L293D or its equivalent (but more powerful) SN754410 is not the same, and does not have the same impacts, particularly on the way the logic and the power supply are separated… And if anyhow you manage to get your motor rotating the way you want, as soon as you put it on load, you’ll discover the whole thing isn’t powerful enough…

Anyway, I couldn’t mention here all the problems I’ve faced. For now, I have a quite nice configuration (after burning/killing no more than 4 PIC), using SN754410 (far better than L293D, less noisy, …) driving my RC tank’s DC motors. Driving both motors makes SN754410 hot, about 85/90°C) which activates its thermal shutdown, thus turning off the whole… But that’s without heat sink DIP. If it persists, I’ll surely need to pick up my recently received LMD18200 or use the driving motor part of the RC tank’s original board… Whatever the result will be, for the time I’ve spent on it, I’ll make a new nice page on SirBot Modules, showing my “DC motor controller board”… And I hope you’ll mention my new BlueSMiRF bluetooth serial modem from SparkFun, which helped me a lot setting I2C communication both mainboard’s and DC motor controller board’s PIC. I need another entry… :)