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Topic: 12v dc motor control with pot and lm324 (Read 2259 times) previous topic - next topic

miahp

Hi,
Does anyone or has anyone done a dc motor control with a potentiometer
and a lm324 op ic? Is it possible? Looking for basic speed and direction
control with the direction of pot and increase of pot sweep. I know there
are h-bridges out there and motor shields, I am currently not interested
in those. Just would like to know if it's possible and if anyone has schematics
and schetch. Something to get my feet wet. If not the I will be purchasing
a SN754410 H-bridge.
Thank you for any help

CrossRoads

LM324 is good for +/-20 to 30mA of current source/sink.
Are you driving really small motors from split power supply (+/-5V, +/-12V)?
http://www.ti.com/lit/ds/symlink/lm324.pdf

If not, then use a real motor driver chip such as the SN754410 you wrote, or an L293 or L298.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

miahp

I will be driving a 12v motor at 1A. Appreciate the reply any idea on wiring this thing up? Saw plenty of post for the sn754410 but am finding nothing for the lm324.
Best regards

CrossRoads

You could have the op amp make a square wave
http://www.facstaff.bucknell.edu/mastascu/elessonshtml/UsefulCircuits/SqWaveGenerator.htm
and drive the 744410 with that as speed control on input 2.
Use a 2nd op amp as inverter to drive input 7. That will get you motor speed.
Use a 2nd pair of op amps to control which output is enabled, for direction.
I think the L293 datasheet shows the control relationships more clearly.

Pin 2 pulsing with 7 low is motor spin one direction. Pin 7 pulsing with 2 low is motor spin the other direction.
The wider the on-time of the pulses compared to low, the more the motor is on, with full speed when the output is just high.
Both 2 and 7 low or both high and the motor does not spin.
http://www.ti.com/lit/ds/symlink/l293d.pdf

http://www.ti.com/lit/ds/symlink/sn754410.pdf
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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