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post #1 of 12 (permalink) Old 08-27-2007, 11:41 AM Thread Starter
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need electrical engineer help :)

I want to do the garage door opener mod to my bike so that I can ride in without having to get out and hit the keypad.

I'm using this how-to:http://kawiforums.com/forum/topic.asp?TOPIC_ID=22049

Basically you hardwire the opener as on, and then use the high beam to turn it on or off by giving it power.

I'm pretty sure my garage door opener is 9v tho. Since the opener will be powered by the 12v high beam line... it needs to be changed in some way down to 9, rite?

So from what I remember in my basic ECE course, I can use a resistor to make sure the voltage across the garage opener is only 9V. problem solved... but finding the right resistor is the problem, since it depends on how much current is going through it. for example if I want to dissipate 3V thru a resistor and the current is 1 amp I use a 3 ohm resistor (Voltage=Current*Resistance)... but how do I figure out what the current is going to be?

hopefully I can do this without frying the electricals on my bike... maybe I should put an inline fuse in there...

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post #2 of 12 (permalink) Old 08-27-2007, 12:18 PM
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I have a different link on a how to. I'll have to check when I get home though...




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post #3 of 12 (permalink) Old 08-27-2007, 04:00 PM
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Originally Posted by Crazy250 View Post
I want to do the garage door opener mod to my bike so that I can ride in without having to get out and hit the keypad.

I'm using this how-to:http://kawiforums.com/forum/topic.asp?TOPIC_ID=22049

Basically you hardwire the opener as on, and then use the high beam to turn it on or off by giving it power.

I'm pretty sure my garage door opener is 9v tho. Since the opener will be powered by the 12v high beam line... it needs to be changed in some way down to 9, rite?

So from what I remember in my basic ECE course, I can use a resistor to make sure the voltage across the garage opener is only 9V. problem solved... but finding the right resistor is the problem, since it depends on how much current is going through it. for example if I want to dissipate 3V thru a resistor and the current is 1 amp I use a 3 ohm resistor (Voltage=Current*Resistance)... but how do I figure out what the current is going to be?

hopefully I can do this without frying the electricals on my bike... maybe I should put an inline fuse in there...
I haven't had a chance to dig into it, but your current drop should be proportional to the voltage drop. To properly size the resistor, you will need to know the amperage on the wire you are planning on using. If you know two of the three (V,I, or r), the last one is easy.

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post #4 of 12 (permalink) Old 08-27-2007, 04:13 PM
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Scratch that, just get you a regulator to take it down to 9v maybe something like LM7809

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Last edited by Trip; 08-27-2007 at 04:25 PM.
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post #5 of 12 (permalink) Old 08-30-2007, 08:16 AM
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After a lenghty discussion with a colleague, we have decided that you need the pop off the postive terminal of your battery and get a total resistance from positive lead to ground, or negative lead. 12 V divided by your measurement of resistance will give you your current. You need a complete circuit resistance measurement because most of the circuits on a bike are in parallel so that you will have no voltage loss to equipment that needs 12 V. Now to figure out what resistor you will need, divide your resistance measurement by 4. whatever that is is the size of the resistor you need to drop it down to 9V.
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post #6 of 12 (permalink) Old 09-01-2007, 06:39 PM Thread Starter
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It turns out, I'm a moron and my opener is actually on a 12V battery.

okay... I got it all wired up, and surprisingly, it works. AWESOME!

I know its a really lame mod ... but its cool to get something like that working and knowing you did it yourself. It only took me like 4 hours, a lot of swearing, a lot of pacing around going "WTF is wrong with you?!?!?"... but w/e ...

I originally wired in a fuse (another retard move on my part)... but that was getting to be a pain because the fuse wire was too big for the wire tap. so i could only put a few strands in... leaving exposed wire. being the retard that I am, I managed to short the headlight wires. so after a 5 minute trip to the hardware store to get a new fuse, thats fixed. Then I said "wait a minute... why the hell am I wiring in a fuse, if the bike already has a fuse for the headlight wires??" so I got rid of the fuse, put the wires in the taps, and boom it works.

here's a thought tho: Say I'm riding along somewhere, and I want to use my hi beams. So I flick it on. Say I'm pretty far away from my garage, so no problem of the door opening or closing on accident. Is it a huge problem that the opener is still transmitting? (would it drain a lot of power??) I would think that it would definitely not drain less than the headlight would, seeing as it uses a tiny battery. right?

I'll post up some video later of how it works.

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Last edited by Crazy250; 09-01-2007 at 06:43 PM.
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post #7 of 12 (permalink) Old 09-04-2007, 09:05 AM
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I am pretty sure you'll be fine. that tiny opener wont drain much if any. A test you could do is disconnect it, turn on high beams than reconnect and see if it has any affect on the brightness of your head light. But that shouldn't be necessary. I just wonder how many other peoples garages you may open riding by with your high beams on!!
glad you got it sorted

Sincerely Your "Squidly" VA rider
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post #8 of 12 (permalink) Old 09-04-2007, 09:47 PM
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Yeah I'm sure it won't drain anything worth talking about. Now you may open a garage or two if you start rollin thru sub divisions with your high beam on.




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post #9 of 12 (permalink) Old 09-05-2007, 04:48 PM Thread Starter
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I don't normally ride with my high beam on during the day anyways, and I don't usually drive at night. so hopefully noones garage will randomly open or close while i ride by

Thats why originally I had the switch inline with the opener, so that if I wanted to I could disconnect the opener from the high beam. (say I was gonna go for a night ride I would turn it off) I might still put it in...

I've been using it for the past week and its very nice. I can just pull right into the garage and close the door behind me. The best part is I dont have to take my hands off the bars. If I had made it a pushbutton thing on the dash it wouldn't have been as nice.

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post #10 of 12 (permalink) Old 09-05-2007, 04:51 PM
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so hopefully noones garage will randomly open or close while i ride by
And if they do maybe you can score yourself some free chit!
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post #11 of 12 (permalink) Old 09-05-2007, 05:07 PM Thread Starter
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post #12 of 12 (permalink) Old 09-06-2007, 12:49 AM
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Or you could do what I want to do on my chop... hook it to the horn.




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