How many power supplies for robot?

Will__S

Hi All,

I've been building a little sumo bot, and was kind of curious if anyone had any tips or rules of thumb for power sources. I've got 4 motors running at 12v, 2 servos, a few very low power sensors(ping, sharp, qti), and the propeller microcontroller. Currently I have a 12v rechargeable battery pack for the motor controller and motors, a 6v AA battery pack for the 2 servos, and a 9v battery for the propeller and sensors (regulated to 3.3v for the prop and 5v for everything else). I was hoping to possibly reduce the amount of separate power supplies, but wanted to see if anyone has had any experience with this.

The 2 servos are on their own supply because I was experiencing some odd behavior from the microcontroller when the servos were strained at all (even just touching them while they were being commanded to stay in one place). I observed over 1/2 a volt drop in their supply when strained and figured the odd behavior was due to a brown-out like condition.

Would a large enough cap allow me to run these 2 servos from the regulated 5v instead of directly powered from the 6v source? Any rules of thumb on how to figure out the size capacitor needed to smooth the power demand?

Any recommendations on consolidating the supplies? Dos or don'ts? Should I be worried about the amount of current the single 12v source could supply if I chose to consolidate to this source only?

My equipment:
spin studio mainboard with prop
12v ni-mh 1600mah rechargeable battery pack http://www.lynxmotion.com/Product.aspx?productID=64&CategoryID=48
2 ping sensors, 2 sharp ir sensors -> connect through an adc chip, 2 qti sensors
4 12v motors http://www.lynxmotion.com/Product.aspx?productID=94&CategoryID=11
2 hitec standard servos

Thanks for the help,
Will

kwinn

You can probably run the entire robot circuitry off the 12V rechargeable battery pack if it is carefully designed and built. Connect 2 capacitors (at least 2500uf 16V each) to the 12V battery through 2 separate diodes and have 2 separate switching power supplies (check out the LM2675 data sheet). Have one to provide power to the servos (I am assuming 5V will work), and a second to power the propeller and sensors. Bypass the propeller 5V regulator and use the second 5V regulator to power it directly. Make sure the wires for these supplies are connected at or very close to the battery.

SLUG-1

Batteries get hot and can have substantial weight, the fewer the better. try to balance battery life into the
equation aswell