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Electronics => Electronics => Topic started by: W4rHer0 on May 22, 2013, 11:24:46 PM

Title: voltage through 4wd
Post by: W4rHer0 on May 22, 2013, 11:24:46 PM
i'm building a 4wd robot using arduino Uno r3
the motors im using require 12v
so how am i supposed to pass so much voltage through my arduino without frying it?
someone said i should use an h bridge or a motor driver
could someone tell me how they work?
Title: Re: voltage through 4wd
Post by: obiwanjacobi on May 23, 2013, 01:15:13 AM
You dont!

You can power the Arduino with 12V but it only outputs 5V (and 3.3V) and it cannot source a lot of current on the 5V rail.

If you have one 12v voltage source (battery) then connect it both to the motor controller (H-bridge) and the Arduino. Keep in mind that motors can cause interference on the power rail that might screw up the Arduino (make it reboot or crash). Use the Arduino to drive the control lines of the motor controller.

I have two separate power sources on my robot. One specifically for the motors and one for the electronics. That also keeps the noise/interference down on the +5V rail.

Most motor controllers/driver are H-bridge. You can google that to find explainations. Basically the chip can drive a large voltage/current by sending it some TTL (5V) logic signals - of which one is usually a PWM signal - for speed. Most motor controllers have 2 separate channels that allow you to drive two motors independently.

Important is the amount of current each motor draws at full load. The Motor Controller must be able to handle that current. Because you have a 4WD you may want to drive two motors on one side together - so you have to multiple the motor current by 2. So if one motor draws 1A tops and you tie 2 motors together, you need a Motor controller that is capable of handling 2A (or more) per channel.

Hope it helps.
Title: Re: voltage through 4wd
Post by: jkerns on May 23, 2013, 07:01:09 AM
As stated, you can't drive the motor directly with the arduino.

More than you are likely to want to know about H bridges in a really boring format: (

Best viewed when you need help getting to sleep.
Title: Re: voltage through 4wd
Post by: johnwarfin on May 24, 2013, 10:34:10 AM
if motors only need to go forward like in some rc cars an h-bridge is overkill. a simple transistor will do the job for about 1% the cost and complexity. 2-3amp fets cost a dime or so and only need 3 wire hookup.
Title: Re: voltage through 4wd
Post by: Arduino02 on June 07, 2013, 03:01:42 AM
Arduino Uno R3 only provides the PWM control signal, there is special drive board in the motor drive, L298N H motor drive board and UNO board should provide the power apartly, or the UNO will not work, I suggest you use the L298N Dual H bridge motor control board to control the motor.
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