reverse polarity protection on $50 robot

[cooldog]

i was just wondering if anyone has bothered to implant reverse ploarity protection is the $50 robot or how you would if you wanted to

[Razor Concepts]

A diode? I just fried my mega168 because of reverse polarity 

[paulstreats]

Just a single diode between the +5v and the power regulator should be fine

[Trumpkin]

A diode would lower the voltage though.

[Ro-Bot-X]

A diode would lower the voltage though.

Not a biggie if you power your board from a 9V battery and servos from a separate 6V battery. If you power everythig from a single 6V battery (not gonna work with the regular 7805 voltage regulator), then the voltage drop over the diode can make your microcontroller reset when servos start/switch directions when the battery gets a little drained. If you use a 7.2V battery with a LDO regulator, using the diode is fine => this is what I use.

[Admin]

Use a PFET for a ~0.1V voltage drop reverse polarity protection

http://www.irf.com/technical-info/designtp/dt94-8.pdf

(see top right schematic, and connect load to your voltage regulator)


That being said, I accidentally reversed power to my $50 Robot for a few seconds but nothing broke . . .

[Soeren]

Hi,

A diode would lower the voltage though.

This won't

[airman00]

or get a schotkky - only like .3V drop

[Webbot]

Or an easier solution (although not fool proof) is to use a 3 pin header for the batter supply. With, say, Gnd in the middle, +ve at one end, and unconnected at the other end. Then if you plug it n the wrong way then 'nothing' happens. Or use polarized header pins/sockets.

 Obviously if the header is left plugged in and you try to connect your 9v battery into the clip the wrong way around then it doesn't help. But better than nothing.