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OOPS and also Ouch!

September 5, 2014

I was ready to try my first floor test of the Carbot having sourced a fresh 9V battery to power the olduino(the motors are powered by a separate pack).  When I tried it on the test stand though, it didn’t run and, when I went to unplug the power jack I accidentally touched the voltage regulator which was blistering hot.  I think the olduino part of the circuit is only drawing 50ish ma and the regulator, an NTE977 is rated for 100ma.  Maybe dropping the extra 4.5V even at 50ma is too much without a heatsink.  I also wonder whether charging the .22F supercapacitor on the Membership Card might be drawing a heavier current – I’ll figure that out.

Meanwhile I have a cute little pololu boost circuit that can maybe generate my 5V from a 3V supply.



Update: after a bit more fooling around and a look at the schematic I realize that I can’t connect my 5V power to the 5V position on the Membership Card.  There’s a diode on this version of the olduino that was meant to stop the Olduino circuit running off the membership car’s power.  This never worked because the AVR leaked so much through its I/O pins but it does stop me powering the circuit from that spot.  Going in at the serial connector works fine.

Update: I can successfully power the whole setup from the single battery pack but I don’t know how clean the power will be with the motor controller in the circuit:

14-09-05 power circuit 


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