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Constant to Momentary circuit for windows

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Old 10-12-2002, 12:49 PM   #1
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Constant to Momentary circuit for windows

I'm trying to wire a ground output from my alarm (.8 sec, 10 sec, or 30 sec) to make my windows go down. I have already wired the relays in the door, so I can hit the wire (that I ran to the cabin) to ground and the window goes down.
I've been trying to use this circuit from the12volt.com:


Found Here
Only instead of constant fused +12v and momentary 12v output, I'm using ground on pins 87 and 30.

With the 1K uF cap, it's supposed to put out 1/2 sec. output, but I need 3 sec. for my windows so I am using 5.9K uF worth of caps, but I still get only about half a second. Anyone have any experience with this? Is it not a linear increase for time vs. capacity? Is there an easier way?

-Smitty
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Old 10-13-2002, 06:59 AM   #2
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Re: Constant to Momentary circuit for windows

Quote:
Originally posted by DJSmitty
I'm trying to wire a ground output from my alarm (.8 sec, 10 sec, or 30 sec) to make my windows go down. I have already wired the relays in the door, so I can hit the wire (that I ran to the cabin) to ground and the window goes down.
I've been trying to use this circuit from the12volt.com:


Found Here
Only instead of constant fused +12v and momentary 12v output, I'm using ground on pins 87 and 30.

With the 1K uF cap, it's supposed to put out 1/2 sec. output, but I need 3 sec. for my windows so I am using 5.9K uF worth of caps, but I still get only about half a second. Anyone have any experience with this? Is it not a linear increase for time vs. capacity? Is there an easier way?

-Smitty
In all honesty...invest into a DEI module, 530T. It will save you alot of time and frustration.

My $.02

--Don
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Old 10-13-2002, 08:29 AM   #3
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You might be right, but MSRP on dei.com is $147.00, and that's a little too expensive to have the windows go up and down. I got to college, so I'll ask one of the EE professors this week I guess.

-Smitty
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Old 10-14-2002, 04:18 AM   #4
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I can provide the module for you..for alot less than that.

There are several other features as well though. Like windows up when you arm your alarm,one touch windows up and down. roll windows down either all the way, or in increments via your remote.

--Don
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Old 10-14-2002, 01:42 PM   #5
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Ok looks like you are going about it backwards. You need to get a circuit that will keep a momentary ground low for a few seconds instead of limiting a high to a few seconds. Your diagram will take a 12v permanant or switched source and limit it to 1/2 sec tops. The source side will stay at 12v and the rc time constant side (resistor and capacitor side) will start at ground , activating the relay, and charge to 12volts in 1/2 sec. Once it reaches about 9 volts the relay deenergizes because both of its coil contacts are near the same potential.
You need a timer circuit that keeps ground potential for 3 seconds and then floats. You can do this by a similar rc circuit with 1 capacitor and two resistor but it will leave your alarm output vulnerable. I would simply go to radio shack and buy a 555 timer ic. The ic's instructions show you how to build a circuit for under five dollars. And give you values for different durations if you need the output shorter or longer.
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Old 10-14-2002, 10:39 PM   #6
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If the relay switch point will be at around 9V you need to come up with a RC combination that will be at least 3s for one time constant, since 1 time constant will be between 8-9V.

You should be able to increase both R and C to come up with the necessary value. Unless the relay is opening up sooner than with a difference in 3V. You might need to test the relay or at least look at the data sheet for it and determine how much voltage is needed to maintain contact. If it is more than like 3 or 4V you might need to go with a different circuit.
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Old 10-14-2002, 11:30 PM   #7
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Re: Re: Constant to Momentary circuit for windows

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Originally posted by Pearl96Max


In all honesty...invest into a DEI module, 530T. It will save you alot of time and frustration.

My $.02

--Don
Yep, I installed this module last week. Works like a charm. Must choose particular options of what you want the power windows to do. Great option for summertime months. Look on Ebay, they usually have these and the 529T also. I won mine for $56.00!
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