Larger Motor

Nov 05, 2014 3 Replies
O

Device with a DC output to a small variable speed DC motor. Output drives the small motor from zero RPM to max RPM (not sure what max is right now) with full speed range control. Other than a larger PS, what would I need to allow replacing the small motor with a motor with more power? Suggested circuits would be very helpful. Something more than an emitter follower. Something with a little output protection for motor stall etc.


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M

You need a current limiting PS..

How much HP/ (Volt x amps) are we talking about ?

Jamie

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O

Output is 0 to 3v. New motor is 5v 200 ma.

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M

looks like you're after a very simple solution.. Use a LM317 in current limit mode..

.-------------------------. | | | | | | 8..35volts | LM317 Out Pin| +++-------+ +----+--+ | | | | | | | .-. | | Adjust pin | | | 6.3 ohms 1/2 W | '-----------+-------------' | | + | '-' /+\ | + ( ) | | Output \-/ | | + +---------------------+--------------+ | | === GND

About as simple as it gets for such a small current at ~200 mA.

You can also employ another LM317 as a variable output attached to the current limited output shown here. Or, you can use that simple emitter follower circuit attached to the output of this circuit, it's your choice. This is a 1.5 amp part. If you don't use too high of input voltage you should be able to operate it at 200mA with no sink.

P.S. I didn't include it in the above schematic but it maybe wise in your case to have a feed back diode to the input, in case output voltage for some reason exceeds input voltage.

Jamie

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