Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: rcdooley on January 25, 2007, 10:24:31 AM
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Using
4 AA Alkaline Batteries (internal resistance of .4 ohms)
Tamiya 10168 motor gearbox http://www.pololu.com/products/tamiya/0114/
I need to be able to control the motors to operate seperatley and go in reverse
I am planning on using a spdt relay ( for off and on ) and a dpdt relay (for high speed and low speed)
I do not know what size relay to use or how to wire them.
If I run all the AA batteries together I will have a max of six Volts but three Volts for each motor therefore I need a relay less than 3 Volts to make sure the relay will come on?
Thanks,
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how do you plan to control the relays? if you plan to use a microcontroller, using MOSFETs are better than relays. for the el-cheapo motors in that tamiya product, you can use a simple H-bridge IC or cheap motor driver - this would be the route I would go.
but if you were going to use relays . . .
to operate a single motor in both forward and reverse directions, you will need two dpdt relays wired in a configuration similar to that of an H-bridge:
http://www.societyofrobots.com/schematics_h-bridgedes.shtml
since the motors are small and wont draw much power, just get a really small cheap relay. if you wire 6V to both motors, then both motors will still receive 6V. the current will divide by two, not voltage :P
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Then making a transistor H bridge is better, but more complicated so what do i need to do for it to work for my parameters.
Two NPNs and Two PNP, I know how an H bridge is set up but do not know what to get.
I thought Mabuchi motors where good?
I have 6V total but need two motors too run at once and need a High torque, is there a better motor that i could swap out in the dual motot gearbox.
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If you want to make an H-bridge, go to Digikey.com and do a search for 'MOSFET'
in the Packaging/Case section, select all that have TO-220. This gives you a package that you can easily work with on your circuit board, and heat sink too.
Then select your current and voltage that you need.
But I think making an H-bridge is the hard way. I recommend instead searching for 'motor driver' in Digikey. This will give you a simple one package solution.
If you require higher current for your motors, try http://www.dimensionengineering.com/ for larger motor drivers.