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Author Topic: Simple motor driver?  (Read 1492 times)

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Offline nekhbetTopic starter

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Simple motor driver?
« on: July 12, 2009, 12:27:58 PM »
Hi,

I have received as a gift this gearbox : Tamiya 70097 Twin-Motor Gearbox Kit ( http://www.pololu.com/catalog/product/61 ) and I already own an Arduino board. Can I use this gearbox with the Arduino to make a simple robot? I mean .. I searched a motor driver for it (it has 2 x 3V motors that can draw even 2.2 A which is a little to much for L293D) but without luck :(, is any way to limit the current of those motors? or? (Sorry , I'm a beginner in electronics but not in software).

Thanks

Sorin

Edited : I forgot to add the link for the motor specs : http://www.pololu.com/file/0J11/fa_130ra.pdf

Offline Webbot

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Re: Simple motor driver?
« Reply #1 on: July 12, 2009, 12:56:18 PM »
The page you have given recommends using the following motor driver http://www.pololu.com/catalog/product/120
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Offline nekhbetTopic starter

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Re: Simple motor driver?
« Reply #2 on: July 12, 2009, 01:01:17 PM »
Yeah, but it isn't cheap :), I'm looking for a cheaper alternative with standard components so I can build it.

Thanks

Offline Ro-Bot-X

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Re: Simple motor driver?
« Reply #3 on: July 12, 2009, 01:40:13 PM »
You can use 2 stacked SN754410 with heat sinks for a max 2A per motor. I have used only one SN754410 with the twin gearbox and had no problems at 4.8V. Well, I remembered to stop the motors before switching directions and avoided stall conditions by installing bumper sensors all around the robot.

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Offline nekhbetTopic starter

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Re: Simple motor driver?
« Reply #4 on: July 12, 2009, 01:50:16 PM »
Hi Ro-Bot-X (I think I read some of your posts on a romanian forum :) ),

Thank you for the answer :), so ... if I run a simple algorithm like this :

if motor is running
  if the sensor sees no movement in the wheel
    stop motor
  end if
end if

can I use a single 293D to drive both of them safely?

Also .. about the voltage .. isn't 4.8V a little too much? Is it ok to run it like this?

Regards

Sorin

Offline Ro-Bot-X

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Re: Simple motor driver?
« Reply #5 on: July 12, 2009, 03:38:48 PM »
Hi Sorin,

Your algorithm will work fine and keep the driver safe, but I feel like L293 is not enough to drive those motors. But you can try stacking them and see how is going. If you power the motor at a higher voltage the current will be less (because the motor internal resistance is the same), but you risk to shorten the motor's life. These are not so efficient motors and have a tendency to melt the collector when powered at a too high voltage. I had them running on a line follower at 6V and that was a bit smelly after a while. But at 4.8V (4 NiMH cells) they were fine. The only thing I didn't like about this setup was the second battery needed for electronics. I like to use only one battery for everything.

And yes, you can find me on forum.inteligenta-artificiala.ro.
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Offline nekhbetTopic starter

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Re: Simple motor driver?
« Reply #6 on: July 13, 2009, 12:05:53 AM »
Thanks again :)

So, I'll try then with 2 stacked SN754410 (to be 100% sure) as you first suggested :)

Regards

Sorin
« Last Edit: July 13, 2009, 12:07:36 AM by nekhbet »

Offline Ro-Bot-X

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Re: Simple motor driver?
« Reply #7 on: July 13, 2009, 05:20:13 AM »
Make sure you solder 3 ceramic capacitors of 0.1uF (100nF) on each motor like this: one capacitor between the motor's leads, one capacitor from one lead to the motor case, ant the third capacitor from the other lead to the case. This is for reducing the motor noise in your electronics and to extend the motor's life. Also, twist the wires going from the motor to the motor driver.

Good luck with your project and let us know how it turns out! (pictures, video...)

Gabriel.
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Offline nekhbetTopic starter

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Re: Simple motor driver?
« Reply #8 on: July 13, 2009, 05:31:59 AM »
Thank you Gabriel for the advices  ;D, I'll surely follow them.

I will post a link here after I finish it (it may take a little more than a month as I will be in a holiday starting next week).

Offline radhoo

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Re: Simple motor driver?
« Reply #9 on: July 13, 2009, 09:26:48 AM »
Also if you get along with electronics, you can build your own HBrideges, and use components to withstand high currents (eg. big transistors).

Here's what I'm using with good results:
http://www.pocketmagic.net/?p=508

The components are cheap and you can solder them on a test board easily.

Offline nekhbetTopic starter

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Re: Simple motor driver?
« Reply #10 on: July 13, 2009, 12:55:33 PM »
Hi Radu,

Thank you for the schematics :), I will use first the 2 ICs and then, as an experiment the transistor based one.

Best wishes

Sorin

 


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