TEMS LEDs... need some info.

CRE

CRE

7M-GE + MAFT Pro + T = :D
Oct 24, 2005
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Denver, CO
Hey guys, I'm swapping the LEDs on the electronics for another member and the one thing I need to know is how much voltge does the cluster feed the TEMS display? is it ~12-14v?

I don't have TEMS otherwise I'd check it myself.

Thanks!
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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0
Redacted per Title 18 USC Section 798
A little basic electronic theory for youa:

LEDs are not lamps, they're diodes. As such current through them must be limited when they're connected across a power source. The good news is you can run them on any voltage you'd like as long as the current limiting resistor is sized properly. Most LEDs (but not all) are speced to run at around 20 milliamps of forward current. The formula is LED forward voltage minus applied voltage divided by desired current equals the resistance needed.

I realize that doesn't answer you're but the odds are very good the TEMs output is 5 volt. You can measure across the LEDs to check but any LED with a nominal forward voltage rating of 2.8 volts (most, but not all, LEDS) should work in place of the stock ones. If you use LEDs with something other than this rating you'll have to calculate the resistance needed to limit the forward current to spec and then change the resistors.
 
CRE

CRE

7M-GE + MAFT Pro + T = :D
Oct 24, 2005
3,485
0
0
Denver, CO
jetjock said:
A little basic electronic theory for youa:

LEDs are not lamps, they're diodes. As such current through them must be limited when they're connected across a power source. The good news is you can run them on any voltage you'd like as long as the current limiting resistor is sized properly. Most LEDs (but not all) are speced to run at around 20 milliamps of forward current. The formula is LED forward voltage minus applied voltage divided by desired current equals the resistance needed.

I realize that doesn't answer you're but the odds are very good the TEMs output is 5 volt. You can measure across the LEDs to check but any LED with a nominal forward voltage rating of 2.8 volts (most, but not all, LEDS) should work in place of the stock ones. If you use LEDs with something other than this rating you'll have to calculate the resistance needed to limit the forward current to spec and then change the resistors.
Click to expand...

I'm aware, to a degree. But when I tested them using a variable power supply the original LEDs were *extremely* dim. So if figure there's either something wrong with my power supply (it's just a hacked PSU) or the TEMS LEDs require a lot more voltage than I'd expected. So I figured I'd work on the safe side and ask for a known number. With 5v the replacement LEDs are VERY bright.... enough to make me think they're running a bit past their mcd rating. I don't want to mail this back and have them all pop the minute he installs them simply because my estimate was off.

JetJock, the existing reistors are 820Ω. Pretty big for the former LEDs to be rated for anything near 2.8v @ 20mA.... now if they were .5v @ 15mA I could see it. They are original LEDs aren't in any package either, just a die epoxied in place.

I just want to eliminate the need to haphazardly guess. So, anyone have a known voltage?
 
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