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## Motor Question

Hello (EZ_Robot) World!
As an introduction, my name is Chris. I learned about EZ_Robot a few years ago, when my brother started experimenting with a robot project  which he has since almost abandoned. So I've decided to jump on board and get involved and help him continue with  it. My experience in programming is limited to a High School class in the  BASIC language back in 1980, and in the early 90s I took a one day course in HTML. My brother has only learned what he taught himself from the EZ_Robot website. While I have watched a few of the tutorials, and plan on learning from more of them, so far they seem  to be geared specifically toward the indicidual robots sold by EZ_Robot. (If there are tutorials on scratch building, I haven't found them yet.) Our robot is going to be somewhat unique, so I have some very basic questions to begin with that I have not seen covered anywhere yet. First of all, our  Robot is going to be large and heavy. It will be powered by an automotive battery and be running (comparatively) heavy duty Motors instead of servos.  (i.e. windshield wiper motors and power wheelchair motors.) The amperage needed will be too much to run directly through the EZ_B board, so our plan is to run the 12 volts right from the power source to the motors, and switch them on and off using Automotive relays controlled by the easy board. So my first question is,  would  there be any better suggestions then simple Automotive relays? I know those would turn the motors off and on, but I would like to use the pwm feature. Could I do it using relays or not? I was thinking of maybe having the easy board turn servos that would rotate potentiometers controlling the voltage to the motors instead of 'on/off' relays, but I've been told that pwm is better than voltage control for speed of a DC motor.
I'm going to have more questions later, but before I even start I need to figure out this step. Any input would be appreciated. Thanx in advance.

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Synthiam
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Germany
#1
Hi,

I think for a large and heavy robot it is essential to be able to control its speed. You may also face mechanical issues if you switch the motors on and off between zero and full speed. Like stripping gears etc.
If you are going to try and build a electromechanical speed controller,
you may be better off saving the money and have a look at electronic speed controllers. I had a mechanical speed controller 30years ago for my first electrical powered rc plane. It was a pain in the ....
There are RC ESCs for brushed motors, but be sure to pick one that is rated for 12V. They use PWM to control the motor speed, both as input and as output.
Just search for "brushed ESC 12V".
I guess you will need two of them, so you could have a look at the Sabertooth or Roboclaw robot motor controllers. I own a Sabertooth controller and it has some nice features, like a built in skid steer mixer, analogue, PWM or serial input and more.
#2
Simple answer is that you need a motor controller like an H-bridge or a Sabertooth 2x 25 (should be big enough) to control speed and direction of those motors...
#3
You also have a space bar on your keyboard..sorry i couldnt read all that..i need paragraphs or my brain hurts...
#4
@NEWAGETOMY
Sorry for the run on paragraph, but it was text to speech. No keyboard. Don't know how to do space bar with text to speech!

@Richard R & count74
Thanks for the input. I was originally thinking of using cordless drill motors, so I started collecting a bunch of old ones. Then opted to go with windshield wiper motors. And wheelchair motors for The Locomotion. But now I'm wondering if I can use the trigger mechanisms from the power tools as motor controllers for the windshield wiper motors.....
#5
You really want to have a speed controller here. Mechanical relays and rheostat styles of sending power to a motor just don't have the controllability you need. They also make it easy to reverse the direction of the motors. EZRobot can control all of this and is pretty easy to configure to do so.
#6
Do yourself a favor and take Richards advice. Invest in a sabertooth motor controller. It's the only way to go for any kind of robot that you plan to move around on wheels or treads. The bigger the robot is the more important this point is. These motor controllers are amazing and make all the difference in the world.

Oh, by the way. If you want to start a new paragraph when you're using your voice input, just say new paragraph.