[TR] Red LEDs?

David Massey dave1massey at cs.com
Tue May 1 05:50:12 MDT 2018

The red lens will allow red light to pass and filter out other wavelengths.  You can use white LED's and it will work just fine.  That is what happens with the incandescent bulbs in there now.  But red LED's produce only red light so no energy is wasted.

Seriously, there are a couple of reasons to use red over white.  One is that red LED's have a silicon die that produces red light.  White LED's have a silicon die that produces blue light and they have a lens that fluoresces white, much like a florescent tube.  This lens can loose its efficiency over time and put out less light.  Red LED's have no such limitation.  The other is that the red LED's are slightly cheaper.

Another point of trivia.  If you install the Audiovox cruise control with LED brake lights the cruise control will not work.  It took me a day of troubleshooting to figure out why.  The cruise control has tiny solenoid valves that control the vacuum to the operator and the ground return path is through the brake light bulb filaments.  The theory is that when the brakes are applied ground suddenly becomes 12 volts and the solenoids switch off and the operator releases the throttle.  But, with LED bulbs there is no reliable ground path.  Depending on the configuration, voltage across the bulbs can be as high as 9 volts with no current draw.  

I fixed this problem with a relay across the brake light bulbs and used the NC contacts to ground that connection. 



Dave Massey



-----Original Message-----
From: wbeech <wbeech at flash.net>
To: 'Triumphs at Autox Team. Net' <triumphs at autox.team.net>
Sent: Mon, Apr 30, 2018 3:30 pm
Subject: Re: [TR] Red LEDs?

Finally decided to switch to LED bulbs for the TR3 stop/running lights. ISTR
that LED bulbs for the rear should be red to go behind the red lenses.  

Am I correct in this thinking?

Bill B

Sent from my Apple II+

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