AC drill motor question...

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toothless
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AC drill motor question...

Post by toothless » Sat Mar 12, 2005 9:34 pm

Hello, I'm hoping someone can give me a little direction.<p>I am trying to build a wall system that can change its shape. I'm using AC-powered drills to turn a threaded rod that ultimately pushes or pulls on a tube--kind of in a linear actuator type action. The tube is connected to the wall membrane. The motors are activated by push buttons in the floor.<p>The problem I'm running into is that I would like certain floor buttons to have the motor run one direction and other buttons to run the motor in the other direction. The drill's forward/reverse switch is manually toggled on the outer casing. My attempts at taking the drill apart and wiring to the contacts have been unsuccessful.<p>Does anyone have any input on getting the drill to run in reverse without cracking into the motor itself? If you reverse the current in a DC motor it will run backwards, is the same true for an AC motor? Thanks.<p>[ March 12, 2005: Message edited by: toothless ]</p>

rshayes
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Re: AC drill motor question...

Post by rshayes » Sun Mar 13, 2005 4:28 am

You probably can't change the direction on your AC drill without opening the case. The AC line normally changes polarity 60 times per second and the drill runs in the same direction with both polarities.<p>Older drills used a universal motor. This is a motor with both armature and field windings and a commutator with brushes. Usually the field winding was in series with the commutator and armature windings. This will rotate in the same direction with either polarity of supply voltage since the field polarity will be reversed at the same time as the armature polarity. This type of motor can be reversed by reversing the field winding connections. This would require opening the drill.<p>If the drill uses a rectifier and a DC permanent magnet motor, the rectifier will apply the same polarity to the motor with either polarity of supply voltage. This arrangement san be reversed by reversing the motor connections after the rectifier. Again, this would require opening the drill.

josmith
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Re: AC drill motor question...

Post by josmith » Sun Mar 13, 2005 7:12 am

If it has a reversing switch you should be able to extend the wires and use a relay to reverse the motor. A universal motor is similar to a shunt wound dc motor. You have to reverse the field in relation to the armature to get it to run in reverse. The switch on the case is a dpdt switch wired to do just that. Remove the wires and mark them. Ring out the switch function with an ohm meter and duplicate it with the control you are trying to interface.

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jwax
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Re: AC drill motor question...

Post by jwax » Sun Mar 13, 2005 7:57 am

Simplest: Use dedicated drills for the different run directions. :D

toothless
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Re: AC drill motor question...

Post by toothless » Sun Mar 13, 2005 10:48 pm

Thanks for all the replies. I'm sure there is a way to do this properly, but it's just beyond my knowledge. So I'm keeping it simple.<p>I decided to switch to cordless drills, so simply reversing the current makes the motor turn in reverse. I was having problems with shorting when two switces were spliced in, one reversed, so I removed the trigger switch (which only regulates the positive) for a spring loaded physical contact. It's only activated by stepping on it.<p>[ March 13, 2005: Message edited by: toothless ]</p>

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