[Healeys] Now LED's

[Bob Spidell]

Here's an excellent explanation of diodes: http://www.faqs.org/docs/electric/Semi/SEMI_3.html 

It notes LEDs may have a lower breakdown voltage when reverse-biased, but this won't necessarily fry the diode, just allow current to pass when you don't want it to (like in an AC circuit). 

Have reversed a few LEDs, and never seen one smoke. Anyway, the fact you tried and it ruined the unit is sufficient for me--there is probably other supporting circuitry that didn't like reversed polarity and may have given up their smoke. It appears at least one other maker has constructed a polarity insensitive unit. AFAIK, LEDs will only light when properly forward-biased, these units must have some sort of circuitry--DC-DC conversion maybe--that allows this, but it's beyond my knowledge. 


bs 

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Bob Spidell - San Jose, CA 

----- Original Message ----- 
From: "Mr. Bill" <bn1 at pacbell.net> 


Hi Bob Larson, Bob Spindell and List, 

First, I know absolutely nothing about the electrics and doubt I could 
hold a decent conversation with either of you to Bob's! :-( 

I use a homemade display case with three Lucas bulb sockets for my "show 
and tell". The sockets hold a tungsten, halogen and LED bulb for 
comparison. It's powered by my 12V battery charger. I had no problems 
leaving the bulbs on both low and high brightness for extended periods. 
When asked about the positive ground, I sacrificed one bulb by putting 
the charger's positive clamp on the outer (ground) section and touched 
the bottom electrode with the negative clamp. It went puff and let the 
smoke out. 

I anticipate being told that my charger was putting out more than 12V. 
OK, if that's the case, why didn't it blow the LED in the comparison? I 
don't have too many friends with Healeys that are still positive ground 
but I'll try to quickly find one for a true test. Until such time I 
will stand by my negative ground only warning. 

I hope everyone's turkey is/was moist and tasty! 

Bill 
Red Car Enterprises