Re: [DML] #5939 at DCS'12
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Re: [DML] #5939 at DCS'12


LM317 needs the input voltage to be at least 2.5V higher than the output. If 
you use it as a current limiter then the difference is a bit lower at about 
2V. That will mean the LEDs will be pretty dim but they will last forever. 
That is why I mentioned a simple resistor. The LED strips are wired in 
groups of 3 LEDs with resistors to make them run off of 12V. The resistor 
needed to make them work in a car depends on the number of LEDs (number of 
groups of 3 LEDs each). Each group needs 20mA of current so you can 
calculate the required resistance. You should calculate the resistance 
needed for the highest voltage expected. I would say 14.5V is a safe number. 
So, we need a drop of 2.5V at 20mA. R=U/I. 2.5V divided by 0.02A is 125 
Ohms. So, you should use a 125 Ohm resistor for each 3 LED group. If your 
strip has 10 groups (30 LEDs) you will need a 1250 Ohm 1Watt resistor. If 
you can't find a resistor of the exact value go with the next one UP. A 
little higher will be ok. You will not really see a difference in brightness 
but it will extend the life of the LEDs significantly.
LED strips are not designed electrically to be used directly in the 
automotive environment. They can be used if you provide a proper power 
supply. When they said that they can be used in a car they meant their 
mechanical characteristic and light output, ie. water resistant, wide 
temperature resistance and correct color temperature for automotive use. 
Besides, never believe a sales person when they are trying to sell you 
something ;)
Instead of getting angry you could do a little research on the net or just 
ask someone. It's ok not to know everything Bill. Really.

Greetings from Poland!
Tom Niemczewski
Vin 6149 plus 2418, 3633, 5030, 16473, 17086
Google earth: 52°25'17.66"N, 21° 1'58.40"E

From: "DarkStar Media" <darkstarmedia@xxxxxxxxxxx>
Sent: Tuesday, June 12, 2012 7:10 PM
To: <dmcnews@xxxxxxxxxxxxxxx>
Subject: RE: [DML] #5939 at DCS'12

> A really simple circuit using a linear regulator (LM317 should work iirc)
> configured for 12V should help increase your LED lifespan significantly...
> assuming the LEDs have a resistor that are set for 12V.
> Here is a neat little calculator for getting the right resistor for 
> LEDs...
> Note that different color LEDs have different specs for the forward
> voltage... here is a general guide...
> Richard
> -----Original Message-----
> From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf 
> Of
> content22207
> Sent: Tuesday, June 12, 2012 9:10 AM
> To: dmcnews@xxxxxxxxxxxxxxx
> Subject: [DML] #5939 at DCS'12
> It finally stopped raining long enough for me to get #5939's door panels
> back on, so it looks like I may make it to DCS after all (I had to remove
> the panels to dye their carpets black, and to modify my door edge LED's to
> be more easily replaceable:
> .jpg )
> Speaking of which: anyone who tells you that LED's never burn out is full 
> of
> shit. I am bringing one of my old strips so anyone interested can see what
> eventually happens to even high dollar SuperBright brand LED's (#5939's 
> new
> door edge lights:
> jpg )
> I also am driving down on a home made manifold this time rather than my
> usual sand cast manifold:
> jpg
> I have to drive a bus Friday morning/afternoon, but should be in Orlando
> shortly after midnight. #5939 will be indoors this year. I am competing in
> the World's Dirtiest DeLorean category.
> Bill Robertson
> #5939
> ------------------------------------
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