Hello! I am doing a little bit of hobby robotics at home and unfortunately my electronics side is a little bit lacking. I would prefer to share the power supply between the micro-controller and the two DC motors and I know enough to know that in high demand situations the motors might draw enough to temporarily shut down the micro-controller.

So I need to place a capacitor somewhere in the circuit. But my problem is that I don't know where, or of what value or with what additional circuitry I should place it in.

I am using:
-12V worth of AA's
- An old Arduino Decimilia
- 2 small motors that take 3V and have a stall current of 2.1A.

I am trying to learn how to construct this circuit and why it would be constructed like that but I am having a hard time finding the referrence material. Would anyone be able to put me onto something with which i can figure out how to do it?

Cheers

 

Just a rhetorical question, but why do you want to share the power supply between the micros and motors? In this situation, it is better to have separate sources of power.

 

Use a 78L05 5 volt regulator for your micro .
Put a large electrolytic of 1000-2200 uf across your batteries to prevent voltage drops.

What are you using to controll your motors?

 

I think a large cap on the micro's side of the regulator would be more helpful than one on the battery side.

 

Is 2.1 amps reasonable for a AA battery?

You may want to look into another type of battery if not...

Also, why do you need 12V for 3 V motors and an Arduino?

 

According to the specs of the Arduino, it needs 6vdc minimum, preferably 7vdc, so it appears to have an on-board regulator.
What type of batteries are these? You might be able to power the motors and Arduino separately.
Or, parallel the batteries to make a higher capacity 6-volt pack, with a few thousand uf's of caps across the pack.
You could further isolate the MCU supply with a small value series resistor followed by a few 100 uf's of cap's plus maybe a small ceramic bypass.

 

There are a wide range of solutions. I think we're all guessing without more information from the OP about what the constraints are.

Me? I'd consider making a 3V pack with all the batteries and using a small boost converter to roughly double the voltage to power the micro. If the motors draw the voltage of that pack too low, get more batteries. It's not safe to run those batteries at such a high current that the voltage drops that much.

But again, we need to hear from the OP.