Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: cooldog on January 03, 2009, 07:45:17 PM
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okay guys i was wondering if i have a simple circut of a 12v motor and a car battery (12v) with a switch and i put a 12v variable slide resistor in the circut would i be able to control the motors speed?
if what i am saying is true does anyone know where to get a 12v variable slide resistor?
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yes there is....
Google for LM317 speed controller
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http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-3466-5-ND
do you think this is will work?
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Depends on how many amps your 12v motor will pull. The one you listed is good to 5 amps
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would that be max 5 amps from the battery or that my motors draw
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Hi,
The LD1585 will only do for a small('ish) motor.
It can handle around 2W un-sinked and with a large heat sink around 25W tops.
Regulating it to eg. 6V will make it drop 6V (actually a bit more, since the terminal voltage is more than 12V).
Un-sinked this equates to 2W/6V=333 mA
With perfect heat sinking it will be 25W/6V = 4,17A
Regulating the output further down will only worsen this to around 166 mA and 2,1A respectively.
(It's all in the datasheet).
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would that be max 5 amps from the battery or that my motors draw
That your motors draw.
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Here is something far better http://www.dprg.org/tutorials/2005-11a/index.html (http://www.dprg.org/tutorials/2005-11a/index.html)
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Here is something far better http://www.dprg.org/tutorials/2005-11a/index.html (http://www.dprg.org/tutorials/2005-11a/index.html)
that looks like a good circut however i looks like it need a lot of external parts
i would prefer just a off the shelf ready made circut
would that be max 5 amps from the battery or that my motors draw
That your motors draw.
i think that i am moving more toward this option
The LD1585 will only do for a small('ish) motor.
thanks anyway but i would like to use something for a bigger motor so i can use it in future projects
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Hi,
The LD1585 will only do for a small('ish) motor.
thanks anyway but i would like to use something for a bigger motor so i can use it in future projects
Then you really need a PWM circuit, as a linear solution has too much loss (i.e. heat).
You should be able to buy a ready assembled PWM solution, although it might be a bit expensive - perhaps you can advertise for someone here to build the circuit for you, so that you just have to connect power, motor and a potentiometer (eg. your variable slide resistor).
If you want to take that route, stating where in the world you live is not a bad idea.
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well i live near toronto canada