Mirror reflectors turned into turn signals how to w/pics
Senior Member
Joined: Feb 2004
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Wouldn't the holding current drop below spec when the flasher drops out?
My basic train of thought here was there would be a constant voltage at say 9v for the running lights, inside the mirror housing there would be an SCR to block the 9v from reaching the rear l.e.d.'s. When you have the turn signals on the pulse that flashes the led's would be say 14.4v, so if the scr trigger is say 12v, then the scr would latch in when the turn signal pulse is present, but in that moment when the flasher drops out the voltage will drop to 9v, therefor dropping out or unlatching the scr. Then when the flasher closes and sends 14.4v to the leds the whole cycle repeats itself, and would continue until you turn off the turn signal. In effect you would be running two separate circuits thru one wire at the same time and each would work independently.
If my thinking is wrong, please enlighten me.
BTW after my nice holiday meal I'm sitting here enjoying an MGD (I can't stand buttwiper or the rocky mountain moose **** from colorado) while I type this.
cheers
My basic train of thought here was there would be a constant voltage at say 9v for the running lights, inside the mirror housing there would be an SCR to block the 9v from reaching the rear l.e.d.'s. When you have the turn signals on the pulse that flashes the led's would be say 14.4v, so if the scr trigger is say 12v, then the scr would latch in when the turn signal pulse is present, but in that moment when the flasher drops out the voltage will drop to 9v, therefor dropping out or unlatching the scr. Then when the flasher closes and sends 14.4v to the leds the whole cycle repeats itself, and would continue until you turn off the turn signal. In effect you would be running two separate circuits thru one wire at the same time and each would work independently.
If my thinking is wrong, please enlighten me.
BTW after my nice holiday meal I'm sitting here enjoying an MGD (I can't stand buttwiper or the rocky mountain moose **** from colorado) while I type this.
cheersLet's see if this follows:
Initial conditions - given the circuit exact arrangement you described above:
- running lights on (say 9v)
- turn signal / SCR not triggered
Front LEDS = ON ( reduced )
Rear LEDS = OFF
Now - apply turnsignal input:
SCR Latches on positive rising edge
Front LEDS = ON full, flashing
Rear LEDS = ON , alternating from reduced to full brightness
Now - remove turnsignal input:
SCR remains Latched due to continued presence of 9V @ the anode, and the +30ma draw of the rear LEDS (sufficient holding current still present)
Front LEDS = ON (reduced)
Rear LEDS - ON (reduced).
BUT - it gets worse. For any suitable low-current SCR that one would choose for this application, you'll quickly note that the specs for gate triggering are in microamps and fractions of a volt, AND the holding currents are in single-digit milliamps. Both of which kill the deal for the aforementioned suggested design as it currently stands.
Examples: http://www.jameco.com/Jameco/Products/ProdDS/14736.pdf
Even larger higher current SCR's still have inappropriate specs:
http://www.jameco.com/webapp/wcs/sto...0001_160135_-1
At the very least, you'd need to construct a signal-conditioning network to provide a suitable trigger to match the gate characteristics, and you'd still need to deal with the persistent holding current.
IMHO - for the proposed Single-wire design goal, an SCR is the wrong component for the job. You could, I suppose, consider either a Triac or possibly an SCS - again, with added ancillary circuity required. Haven't looked at either closely in many moons though.
Frankly this is best accomplished with an adjustable dual-channel/ dual brightness PWM driver -(regardless of the single-wire goal - I hate diodes and dropping resistors, lol)
Example: http://www.hidplanet.com/forums/show...hback-NOT-gate
Plus many more freely available 555-based designs on the Web.
..... OR - run separate wires to the mirror.
Make any sense?
MGD
Last edited by MGDfan; Dec 26, 2014 at 08:43 AM.
Technical Article Contributor
Joined: Mar 2005
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From: OH-IO
I guess I was wrong. I thought the scr would drop out when the voltage dropped below the trigger voltage. I don't even know what an SCS is, never heard of it.
Oh well, back to the drawing board.
Oh well, back to the drawing board.
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Joined: Mar 2015
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man o man, its finally here, found me a weekend project! i only have one question and thats where did u buy the l.e.d strip at.. what are the specs on it? Very nice write up, if we all lived up to this can of how-to, we'd all be 
some pretty tricked out trucks.
Technical Article Contributor
Joined: Mar 2005
Posts: 4,387
Likes: 9
From: OH-IO
I was out in the garage organizing my tool box and found the led strips I bought last year for this mod and never put in due to the weather. So today I put them in. I didn't get any pics, there is plenty of them in this thread already. I did solder the wires and heat shrink them when I was done.
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Joined: Aug 2015
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If you have power mirrors, the turn signal wires are there. if you don't have power mirrors, no wires are there, and you'll have to rig it up yourself.
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Joined: Jan 2016
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From: Oklahoma
Can you tell me what size connecters you used? Does it matter? Would it be better to put the lights into the lens and seal it together? What type of led do you recommend? What length do you use? Lots of questions, just trying to save allot of trips to the parts store. Are yours sill working?
Member
Joined: Mar 2015
Posts: 29
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From: NE Iowa
Hi all you electronics whiz kids or not so kids.
Without searching or going through all of this thread how about a sequential turn in the reflector and say three smd, cob. Cob and smd is about all I know about LED terminology so make it simple please for the old dog who knew generators, points type voltage regulators and other ancient technology such as when a transistor radio was an expensive new tech gadget!
Without searching or going through all of this thread how about a sequential turn in the reflector and say three smd, cob. Cob and smd is about all I know about LED terminology so make it simple please for the old dog who knew generators, points type voltage regulators and other ancient technology such as when a transistor radio was an expensive new tech gadget!