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sam3s4c Hang

Posted: Tue Oct 18, 2016 7:17 am
by ramar_be
Hi dear,

I am using sam3s4c micro controller.using gpio pin out we are connect 12v relays.without connecting relays controller working fine.. In Firmware we are using watchdog. with connecting relays controller should be hang and also controller reset button not working and programmer reset also not working. Only the way is switch off/on controller..Please solve my query.. thanks in advance..

Re: sam3s4c Hang

Posted: Tue Oct 18, 2016 8:39 pm
by blue_z
You could be drawing too much current from the GPIO pin(s).
Use Ohm's Law to calculate the current required by the relay's primary.
Compare that to the spec in the SoC datasheet.


Re: sam3s4c Hang

Posted: Wed Oct 19, 2016 6:55 pm
by tsvoipio
If you connect 12V relay coils directly to the I/O pins, you are lucky if the chip has not blown up. The absolute maximum voltage on the I/O pins is 4V.

You need to use a relay driver chip, e.g. ULN2003, and the coils need diodes to control the inductive voltage kick on turn-off.