Power Protection

Other Hardware Motors, Mechanics, Power and CNC
1

I'm building a robot wall-racer car. Time for a cleanup! | olduino

I'm powering the motors with a 4.5v battery pack and at present I have the logic circuit powered by a separate voltage regulator and 9v battery. The logic draws about 50ma. I don't really know the draw of the motors. I'm using a pololu MD08A motor driver Pololu - TB6612FNG Dual Motor Driver Carrier.

I have a pololu 5V boost regulatorhttp://www.pololu.com/product/798 which would easily supply the 5V for the logic from the car's battery pack but I'm nervous about spikes. Is the circuit below safe? Can I improve it by putting a diode before the motor driver? I don't want to do this if I don't have to because it will waste motor voltage.

2

If you're worried about spikes put 0.1 uF caps on your arduino 5V lines and use a large Electrolytic (1000 uF or greater across the 5V line. ) That will suppress any spikes and keep the logic voltage stable.

3

raschemmel:
If you're worried about spikes put 0.1 uF caps on your arduino 5V lines and use a large Electrolytic (1000 uF or greater across the 5V line. ) That will suppress any spikes and keep the logic voltage stable.

Wow: 1000uF is a big cap! Did you mean on the 4.5V battery supply?

I'm mostly concerned about some kind of motor-generated transient frying the boost regulator circuit.

4

No. I said across the 5 V..
You're the one nervous about spikes. You asked what you needed to protect yiur logic power andvthat,:s my ansqer.

5

Being a standard boost circuit if the input voltage is too high it will sale through to the output
and destroy it.

I'd keep with separate supplies, it works and one failure mode is removed.

6

Putting the large Electrolytic cap across the boost regulator would also help.