# Electronic circuit help



## Lee L (Aug 15, 2002)

So, I had a garage door opener rigged to a swtich I installed in an open spot in my wifes Jeep. The remote ran on 12 volts so it was a dead simple thing to hook up. Now, we have a new opener and it uses 6 volt remotes and no 12 volt are available for that kind of system.

I took some electronics classes in high school and college but that was a while back and only rememebr enough to be dangerous here. Can I measure the resistance of the remote and use a resistor in parallel with it to get the voltage from the car down to close to the 6 volts the remote needs? I'm assuing that halving it would be OK though I suppose I could go a little under on the resistor to account for the potential higher 14 ish volts when the car is charging.

The other alternative is to buy a converter which is sold ready made, but they are $20 bucks or so and made to plus into the lighter so are huge (I suppose I could take it apart though) and it seems like a giant waste to stick an actual power supply under the dash if I don't have to since it will be used twice a day for 2 seconds.

Am I smoking crack here?


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## P Smith (Jul 25, 2002)

Parallel resistor is wrong idea. You'll need 7806 and couple electrolytic capacitors.

"7806 employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If proper heat sinking is provided, it can deliver over 1 ampere output current."


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## Marlin Guy (Apr 8, 2009)

I assume that the remote originally runs off of batteries, like 4xAA?
I'd just keep it simple and buy the batteries.


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## matt (Jan 12, 2010)

You could use a resistor _similar_ to what you are talking about but I would use a more formal design with a voltage regulator.

This:
http://www.radioshack.com/product/index.jsp?productId=2062601

and the proper resistors/caps.


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## P Smith (Jul 25, 2002)

He can't use a resistor in that manner what he talked. 
Why he need to build something from RS, when he could use just one linear regulator 7806 ?


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## matt (Jan 12, 2010)

Similar was the key word there. Of course you can't do it in parallel, you would just put 12v across the resistor and 12v on the remote.

I suggested the LM317 because he can get it locally and have it all done tonight. 7806 would be fine too.


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## P Smith (Jul 25, 2002)

7806 would be best and easiest solution.

A word "Similar" cannot be used here: 'in parallel' is not similar to 'in series'. Ohm's law !


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## matt (Jan 12, 2010)

Similar in simplicity and parts. What are ya, the impedance police? :rolling: 

EDIT: Yeah, I know impedance is frequency based...


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## Nick (Apr 23, 2002)

If I recall my basic PI/E electronics from 50+ years ago*, a resistor of adequate value wired in series to drop voltage will do the trick.

* _yes, dammit, we had electrons back then!_ :ramblinon


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## matt (Jan 12, 2010)

Whatever Ben Franklin, with your electron flow...


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## Lee L (Aug 15, 2002)

OK, I was thinking series maybe. Good thing I checked before doing anything. Plus, I have no idea how to hook up a voltage regulator correctly. Will it have a pinout if I buy it from Rat Shack?

The remote actually takes 2 CR2032 batteries stacked together for 6 volts. The reason I want to wire it into the car is for a couple of reasons. One, it is a Jeep, so its never secure and as long as it is not actually raining, my wife will usually have the top at least partially down pretty much from the first warm day in March till sometime in November. The low was 45 this AM and she drove with the sunrider part (the front couple of feet fold back)and back window open. So, theft is a real possiblity, even if just from some punk kid being funny grabbing it off the visor. Also, it can just fall off as the Jeep visors are not very think and even with kinking th eclip, it is not that tight.

Plus, she just likes having it with a button in the dash. I bought a Jeep switch so it snaps right in and looks factory and no one would ever know it is the grage remote unless they saw her push it so even leaving it in the driveway at night it is pretty secure.


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## jerry downing (Mar 7, 2004)

Nick said:


> If I recall my basic PI/E electronics from 50+ years ago*, a resistor of adequate value wired in series to drop voltage will do the trick.
> 
> * _yes, dammit, we had electrons back then!_ :ramblinon


That may cause trouble because there is little or no current flow when the device is not being used. As much as 14 volts will appear across the device. It is likely that the electrolytic capacitors in the device are rated at less than that.


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## matt (Jan 12, 2010)

The back of the package at radio shack has a diagram and little formula for figuring out your voltage. Just get the two capacitors indicated, the resistor (I beleive 240 ohm or something close to that, it will say) and a 5k or 10k potentiometer. Connect it as shown in the diagram and dial it in with a volt meter.


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## P Smith (Jul 25, 2002)

Sounds like RS salesman ...


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## houskamp (Sep 14, 2006)

7805 is a standard part at radioshack http://www.radioshack.com/product/index.jsp?productId=2062599

5 is close enough to run that remote.. very simple part.. in/out/ground.. and pinout is on the back of the package.. won't even need any heatsink for your use..


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## Lee L (Aug 15, 2002)

Thanks for all the help.

I was able to get it up and running using the 7805 regulator from Radio Shack. A little more difficult than the previous one as the Genie remotes we used to have not only use a 12 v battery, you can just jump accross the switch and when you apply power, it works fine. The new remote was a Chamberlain and it would not work that way. I had to run seperate lines out for the switch and power leads.


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