benzeman
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Motors

Sat Oct 27, 2012 5:53 pm

Can anyone recommend a pair of motors (preferably from rapid electronics - http://www.rapidonline.com/) for gertboard? I wanna make a pi-bot! Cheers :)

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joan
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Re: Motors

Sat Oct 27, 2012 7:38 pm

I couldn't see anything there which I'd use.

I'd go for an ordinary DC (not stepper) motor with integral gearing with an rpm of circa 100.

e.g. http://www.ebay.co.uk/itm/25mm-12V-120R ... 0673226474

http://www.ebay.co.uk/itm/6V-DC-100RPM- ... 0656700703

Thinking about it I might well buy a magician chassis http://www.hobbytronics.co.uk/robotics/ ... ot-chassis simply for the motors. Not the best but certainly adequate. It was on sale somewhere for under £10.

benzeman
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Re: Motors

Sun Oct 28, 2012 7:50 am

What's the voltage on the motor output? I thought it was only 3.3v?

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Gert van Loo
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Re: Motors

Sun Oct 28, 2012 8:33 am

The Gertboard has only one motor controller. So it is not ideal for a robot.
But the controller works up to 48V and 4A so the motor you use can be a rather powerful one.

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joan
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Re: Motors

Sun Oct 28, 2012 10:07 am

benzeman wrote:What's the voltage on the motor output? I thought it was only 3.3v?
The 3.3V is probably the logic level voltage of the Gertboard, i.e. the level at which signals will be sent to control the motor controller on the Gertboard. The motor controller will switch the probably higher voltage required by the motor itself.

benzeman
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Re: Motors

Sun Oct 28, 2012 10:49 pm

Gert van Loo wrote:The Gertboard has only one motor controller. So it is not ideal for a robot.
But the controller works up to 48V and 4A so the motor you use can be a rather powerful one.
And there's no clever way of running two motors off one controller? Shame...

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mahjongg
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Re: Motors

Mon Oct 29, 2012 12:02 am

benzeman wrote:
Gert van Loo wrote:The Gertboard has only one motor controller. So it is not ideal for a robot.
But the controller works up to 48V and 4A so the motor you use can be a rather powerful one.
And there's no clever way of running two motors off one controller? Shame...
The gertboard is used to teach principles, (the PI is about for education, remember) you can take any section of the gertboard and replicate it for your own use. The PI also has just one hardware PWM output, if you need more you need software PWM if your application is suitable, or use extra hardware to generate PWM signals, or control a microcontroller with extra I/O, as on the gertboard.

nr.
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Re: Motors

Tue Oct 30, 2012 3:38 pm

Completely ignoring the original question, but this may be of peripheral interest. I made a small desk fan using a pair of EDF-55 fans with GWS motors and a 3s1p Li-Po pack. Well, I say small, but it was enough to clear my desk, and most of the floor of any loose paper. I blew the 2A fuse when I ramped it straight up to full power rather than a slow start, so I replaced that with a 5A fuse (sorry Gert! I didn't have a 4A to hand). I stopped using it in the end when I noticed how hot the motor controller was getting, and that combined with the unrecommended fuse made me stop in the interests of preserving the Gertboard.

Good fun though. I also had it controlled from a DS18B20 temperature sensor, so when the temperature got above 22 degrees the fan automagically came on. This is, of course, spectacularly pointless in a shed where the most efficient form of heating is when I leave my soldering iron on for too long. Maybe next summer I'll resurrect the project.
--
nr.

stuartcullen730
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Re: Motors

Thu Nov 01, 2012 5:09 pm

Have you checked out the MAGPI. (Raspberry Pi magazine)?
There is an story about making a PiBot.
Basically it says the use of motors and gears put together by a common user is a wate of time and money.
So CHEAT.
Pick up and old (Yard sale, goodwill, whatever) Toy tank or car.
This not only provides mounted motors and correct gears, sometimes a compatible battery compartment.
The October issue starts the story with, hopefully, more in the November issue.

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