Let's Make Robots!

Need assistance with potential Arduino bot.

First off I apologize if I broke a rule by putting assistance in the title. Now about my problem: I am putting together a parts list for a Arduino version of the Start Here robot. I am not sure if I need a motor controller shield for the Arduino board. I am going to use 2 4.5v DC motors and a ultrasonic rangefinder sensor(5V according to yourduino.com) and I don't know if the Arduino Uno board can handle the power requirements. I was going to use a 6AA power pack to power the whole thing. If you notice any problems about my plan please tell me and if you could answer my question that would be great!

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I drove my motors using just a couple of high amp rated transistors as gates because I was only driving the motors in one direction. I don't remember which ones but they were just what I had in my parts bin.

For my next one I picked up one of these for $3 but haven't hooked it up yet. They're rated up to 36v and 1amp continuous.

I also recommend using flyback diodes to prevent the motor from potentially smoking your stuff with reverse current. If you're driving the motors in both directions it takes double the diodes to do it and you hook them up like this instead of reverse biased in paralell with the motor.


The breakout board Terry linked above has such protections built into it as well as a couple of other bells. In fact it's the same IC in the schematic and the driver board.


About Motor Drivers: Hi Monty,

Sorry I just saw this...

Yes, you need a motor driver, and probably the lowest-cost one is:


If you use the YourDuinoRobo1 version of Arduino you will have cable connectors for many things and make wiring somewhat easier:


I am in the process of doing a simple robot build with a Dagu base with the 4.5V motors. Maybe we can share experiences..




microcontroller pins can only handle 20 to 40 mA depending on the specific microcontroller you are dealing with. Many motors require 100+ mA to just run, and, stall current is usually double free running current. If you pull too much current on a microcontroller pin, you are going to at the very least going to damage the pin that you pulled too much current through.

So, as David said, you will need a motor controller shield for your motors.

Unless this is a special arduino that has a built in motor controller.