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Simple motor and relay help

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dbtoutfit

Member
Hi,

I have a dc motor from a power drill that I am using to drive all thread to move a plexi glass window that slides and hide into the wall up and down.

What I am hoping is I can drive this motor by one momentary switch.
I would like to push the button and it drive the window up out of the wall untill it hits a limit switch which in turn switches the motor into reverse and the next time the button is pressed the motor drives down and stops when it hits the limit switch and the cycle continues up and down.

I will be driving the motor with 12v cd from a computer power supply.
I think the motor might be spinning a little fast when powered straight from the power supply and so I may need some type of speed controller.

Eric
 

ke5frf

New Member
A relay H-bridge set-up with your limits would work.

Follow the link that I quickly found here:
Untitled Normal Page

And a modified , application specific implimentation of this basic design will work if I understand your need.

As far as speed goes, you might just consider a gearbox or even the variable speed circuits from the drill you salvaged.
 

MikeMl

Well-Known Member
Most Helpful Member
Motor reversing and limit switching
 

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KMoffett

Well-Known Member
Mike,

Very simple! Is there a mechanical linkage you envision for the single limit switch? As in some sort of toggle?

Toggle switches always makes reversers easy. Two pushbuttons...a little more complicated. One pushbutton...even more complicated...mine.

Then again...a push-on/push-off SPDT with you circuit....Mini SPDT 3-Amp Push On/Push Off Switch - RadioShack.com :)

dbtoutfit,

What was the normal voltage for the drill motor, and did it come with a variable speed trigger?

Ken
 

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  • MotorPushUpPushDownReverser.gif
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dbtoutfit

Member
Hi,

It was an 18volt drill and does still have everything attached.

when I apply power to it the trigger doesn't work.
I have to go straight to the motor.

My guess is the transistor, mosfet or whatever it is inline has gone bad. I dont know how to test them but I only have continuity through the center leg and the two outside legs ive got nothing.

Eric
 
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KMoffett

Well-Known Member
Best way to reduce the speed depends on what's convenient and works for you. An 18V cordless drill draws quite a bit (pun intended) of current. The most torque at slower speed is developed with an external gear or pulley/belt mechanical speed reduction. A series resistor or linear voltage regulator might do the speed reduction job, but dissipates a lot of heat. The best electronic way is a PWM (pulse width modulation) controller. There a lot of simple (relatively) circuits that use a LM555 IC and MOSFET transistor.

Ken
 

tblo163

New Member
polarity reversing & speed control.

For dc motor reversing,you will need to use relays,simple reversing switches can't cope with the ampage,two 5 pin CO relays (16 amp)& a 3 position switch,is all you need.a good source for them is the local car breakers'
For speed control,a PWM is far the best choice,but don't buy one from China (ebay) they will fail because the heat sinks are too small.Build your own.A simple PWM can be populated on a small piece of strip board quite cheaply.
But you must never run it without a heat-sink.Use a LM324N for the driver,& a high powered mosfet,it can be controlled by remote with a pot.
I'VE BEEN TRYING TO UPLOAD PDF DATA SHEETS TO HELP,BUT THEY HAVE FAILED,I WILL KEEP TRYING!
 

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  • polarity rev.pdf
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tblo163

New Member
Speed control

Here's 2 more hope they get through
 

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  • PWM.jpg
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  • LM324N.pdf
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tblo163

New Member
Volage regulator

IT'S very strange,but I HAVE TO UPLOAD FILES seperately,never had this problem before!
 

Attachments

  • VOLTAGE REG.pdf
    1.7 MB · Views: 114
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