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I'm still new to the Arduino game, but I've been reading quite a bit over the last few days.  My problem is that I'm trying to drive a robot that weighs ~35lbs with 2 rear motors.  I figured that I'm going to need about 160 W per motor to drive 3mph up a 30 degree incline.  So if I were to use a 24 V motor I'm still looking at 6.67 A.  However most of the H-bridges I've seen are only rate for 2A or less.  I need both speed and directional control of both motors.

I'm also looking to just have an on/off motor on the robot which is larger, the motor is rated for 24V 15A.

What is the best way to approach controlling motors this size?  I might be missing or messing something up since this is my first time selecting a motors. 
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Hi Fastpace,
You need to build your own H bridge.
you could use the Arduino to control an H bridge IC driver like this:
http://www.intersil.com/data/an/an9405.pdf
And use mosfets like these http://www.irf.com/product-info/datasheets/data/irf3205.pdf
Also note that you need proper high voltage protection diodes to protect the mosfets and driver ic's from high voltage flyback/inductive collapse spikes.
Info http://www.modularcircuits.com/h-bridge_secrets1.htm

You should probability plan for much more than 160watt.
Dc motors can have very high amp draw while startup.
And when you stall them the only current limiting factor is the motor coil resistance which could very well be below a few ohms. So if that motor has a 1 ohm coil and you supply 24 at 100% throttle the watt could reach 576watt.

Regards,
Steven

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Hi Fastpace,
You need to build your own H bridge.
you could use the Arduino to control an H bridge IC driver like this:
http://www.intersil.com/data/an/an9405.pdf
And use mosfets like these http://www.irf.com/product-info/datasheets/data/irf3205.pdf
Also note that you need proper high voltage protection diodes to protect the mosfets and driver ic's from high voltage flyback/inductive collapse spikes.
Info http://www.modularcircuits.com/h-bridge_secrets1.htm

You should probability plan for much more than 160watt.
Dc motors can have very high amp draw while startup.
And when you stall them the only current limiting factor is the motor coil resistance which could very well be below a few ohms. So if that motor has a 1 ohm coil and you supply 24 at 100% throttle the watt could reach 576watt.

Regards,
Steven



I was looking at using mosfets, but honestly I think I'm getting way beyond my knowledge if I'm designing the circuit for the motor control.  I was looking at Pololu's high-power motor drivers, would these be able to do what I'm looking for? http://www.pololu.com/catalog/category/82

Or would it be easier to interface to the arduino using the high-power simple motor controllers through serial?  http://www.pololu.com/catalog/product/1383

This is my first robot, but I'm jumping in head first since it's part of my senior design project.
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You are not required to use a motor driver shield with an Arduino.  There are plenty of generic h-bridge motor drivers out there capable of providing far more than 6+ amps of power.

http://www.dimensionengineering.com/Sabertooth2X12.htm can handle 2 12 amp motors as just an example.

They all can easily be controlled via an Arduino.  And if you've got a 35 pound robot, you shouldn't have any trouble finding mounting space for additional boards.
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You are not required to use a motor driver shield with an Arduino.  There are plenty of generic h-bridge motor drivers out there capable of providing far more than 6+ amps of power.

http://www.dimensionengineering.com/Sabertooth2X12.htm can handle 2 12 amp motors as just an example.

They all can easily be controlled via an Arduino.  And if you've got a 35 pound robot, you shouldn't have any trouble finding mounting space for additional boards.

Thanks for the suggestion, I was looking at ordering those when I walked into our E-shop at school and we found a pair of Victor 883s and an Arduino Atmega328.  They weren't sure that everything worked but the motor controllers have been used quite a bit and the caps and mosfets look good, and the arduino appears to be good too.  Talk about hitting the jackpot, now I'll just need to make another trip in search of some motors later this week.
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Yes that http://www.pololu.com/picture/0J2223.600.jpg  seems like a nice little board. It supports the raw input to the H driver. So you still need to supply raw pwm signals to the input of the beard. And the native pwm frequency of the arduino is about 480hz if I remember correctly. This is rather low for driving motors. I works great but it is a rather noisy tone. Although Much more expensive, this is also a nice dual motor board which comes with good documentation and software: http://www.robotshop.ca/roboteq-ax1500-robot-controller-1.html It has a nice set of input features. You can input serial. Analog and RC meaning that it takes a servo signal. This could be interesting for you since you only need the arduino to output an single variable pulse width 50hz signal to control speed and direction. So you can use the arduino servo libary. Servo info: http://www.seattlerobotics.org/guide/servos.html The board also supports potmeter feedback. So with that you turn a big motor and a potmter into a very high power servo. The board deals with the PID http://en.wikipedia.org/wiki/PID_controller which is handy. Since it can all be adjusted in the included software. If you were to code that PIC yourself in the arduino environment it would be a big task to get right.

Hi Fastpace,
You need to build your own H bridge.
you could use the Arduino to control an H bridge IC driver like this:
http://www.intersil.com/data/an/an9405.pdf
And use mosfets like these http://www.irf.com/product-info/datasheets/data/irf3205.pdf
Also note that you need proper high voltage protection diodes to protect the mosfets and driver ic's from high voltage flyback/inductive collapse spikes.
Info http://www.modularcircuits.com/h-bridge_secrets1.htm

You should probability plan for much more than 160watt.
Dc motors can have very high amp draw while startup.
And when you stall them the only current limiting factor is the motor coil resistance which could very well be below a few ohms. So if that motor has a 1 ohm coil and you supply 24 at 100% throttle the watt could reach 576watt.

Regards,
Steven



I was looking at using mosfets, but honestly I think I'm getting way beyond my knowledge if I'm designing the circuit for the motor control.  I was looking at Pololu's high-power motor drivers, would these be able to do what I'm looking for? http://www.pololu.com/catalog/category/82

Or would it be easier to interface to the arduino using the high-power simple motor controllers through serial?  http://www.pololu.com/catalog/product/1383

This is my first robot, but I'm jumping in head first since it's part of my senior design project.
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Why not use a RC car ESC? they take a PWM input and the large ones can take some serious power running through them.
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