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Question about batteries and voltages


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Hiya, quick question since my general electronics skills were almost non existent before this project.

 

For my car project i'm using the 6x AA battery unit from the original car for the drive power. Can i use the ground from that, and attach a wire after the 2nd AA battery to tap off about 3 volts for the board containing the MSP? Or will that not work. My guess is no, but if possible it would save me either an extra battery pack inside, or voltage regulator circuitry.

 

Thanks, and Cheers!

 

MarkoeZ

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Can i use the ground from that, and attach a wire after the 2nd AA battery to tap off about 3 volts for the board containing the MSP?

That depends on several things:

What kind of inputs (if any) to your micro will you be using? +3v? +9v? (not a good idea)

What kind of inputs will your micro's outputs be interfaced with? +3v pull-up, +9v pull-up (again, not a good idea), high impedance?

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This is simplified schematic, for illustrative purposes only. I should've used rectangular load symbol :)

(updated schematic with diode.)

 

Safety first, right? :D

 

Oh, and to O.P., you should keep in mind that hooking it up that way can lead to uneven wear on the batteries. Probably negligible considering the msp's low current usage, and the intended platform (High current RC car). Just a heads up.

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This is simplified schematic, for illustrative purposes only. I should've used rectangular load symbol :)

(updated schematic with diode.)

 

Safety first, right? :D

 

Oh, and to O.P., you should keep in mind that hooking it up that way can lead to uneven wear on the batteries. Probably negligible considering the msp's low current usage, and the intended platform (High current RC car). Just a heads up.

 

Thanks for the heads up, but yeah, the 3 volts is only powering the msp430, a shiftregister and a couple of leds. So should not make a noticable difference i think.

And most of the time it will be powered by usb anyway. I was just looking for a quick fix to do standalone tests. With the motherboard, 2 added module boards and the original car drive board (using the h-bridges from that, and it has protection circuitry as well) the inside of the car is getting a bit cramped ;).

 

Cheers!

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