Converting a DPDT switch

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  #1  
Old 04-03-15, 12:00 AM
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Converting a DPDT switch

Hi guys,

I'm kind of poking around in the dark here, but hopefully someone can help me out. Here's the deal:

I have a DPDT rocker momentary switch that controls a 12V motor. Press and hold the switch one direction, the motor opens a door until it's all the way open. Vice versa, door closes until all the way closed. Opening/closing takes about 3 seconds.

If the switch is kept depressed in either direction, the motor will continue to receive power and would most likely burn out eventually.

My goal is to convert the momentary rocker switch to a single push-button switch. For example, the switch is pushed and the motor operates until the door is all the way open. Press it again, motor closes the door all the way.

I'd like to accomplish this without having to modify the motor or door.

Is there a way to use relays to accomplish this? Something else? I'm somewhat familiar with the standard 5-pin relay but that's it.

If this is possible, what type of switch should I use?

Thank you in advance!
 
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  #2  
Old 04-03-15, 01:07 AM
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What is the door you are talking about and what type of motor, especially amperage, are you using ?

The perfect part for your application is a window roll module. One touch up or down. The module monitors the current draw of the motor. When the motor stalls.... the current peaks and the module shuts off the power.

The Directed unit below is a good unit to use for your project. It's available from many places. It's called a two window unit which means it controls two windows with one button auto down only or one window with one button auto down or up.

Directed 529T (dei-529t) Window Control Modules
 
  #3  
Old 04-03-15, 03:26 AM
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I don't see any specifications on that 529T module. It looks like it still needs the cars window roll module. Also not listed is the current draw in standby mode which would be important if your running off a battery.

What you want to do would be real tricky to do with relays. You really need some electronics to do the logic and shutdown timing.
 
  #4  
Old 04-03-15, 08:39 AM
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It's a small motor about the size of 4 AA batteries packed together. Unsure of amperage because it's not listed anywhere. It opens a butterfly valve on an electric cutout on a vehicle's exhaust.
 
  #5  
Old 04-03-15, 08:55 AM
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The 529T is self contained with relay. You supply it with power, connect it to the buttons and it has direct relay switching. However, it needs to work with a motor that draws better than 5A.

We're going to need to check further.
 
  #6  
Old 04-03-15, 12:34 PM
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It's a small motor about the size of 4 AA batteries packed together. Unsure of amperage because it's not listed anywhere. It opens a butterfly valve on an electric cutout on a vehicle's exhaust.
What you are attempting to accomplish was done about 70 years ago in a two speed rear axle switch for a straight truck. Basically a 2 position 3 pole switch on gear stick controlling a motor with threaded shaft that rotated one direction until it encountered internal stop for end of travel, and then when you flipped the gear stick switch the actuator rotated the other direction running the screw the other way until it encountered internal stop in that direction. The stops are contact points that open that direction circuit and stop motor.
A little research on two speed axle electric shift will yield what you are searching for.

Good luck!

RR
 

Last edited by Rough Rooster; 04-03-15 at 02:38 PM.
  #7  
Old 04-03-15, 12:53 PM
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The problem is knowing when it has reached end of travel. Most likely is a current switch using a PLC this is easy by not so sure with relays on how you would latch the relay likely using a JK flip flop would be the hard ware method.
 
  #8  
Old 04-03-15, 02:19 PM
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Or a timer set a little longer than the time it takes his door to fully open or close. That timer could shut off the motor power. I have done these things with microprocessors and MOSFETs.
 
  #9  
Old 04-03-15, 04:18 PM
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You need to set up a circuit that monitors current draw. It will detect when the motor has stalled. The easiest way to detect current flow is to put a resistor in series with one the motor leads and then monitor the voltage across the resistor. When the voltage rises xx amount it means the motor is stalled.

This type of circuit would require you to know the current draw of the motor in the normal running state. You would probably end up using somewhere around a 1 ohm resistor maybe at 5 watts.
 
  #10  
Old 04-03-15, 05:14 PM
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http://www2.dana.com/pdf/AXSM-0029.pdf

Here it is and it is currently available through Spicer.

RR
 
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