LED/ electrical ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72chevyLWB · 07-01-2002, 08:02 PM

I have an LED bar from a 98 S-10 3rd brake light. Now, these lights are in series right? So can I just cut off which ones I don't need because its too tall. I am going to do 2 or 3 rows of LED's in each tail light going up and down. I just need to find out how to trim them down. Heres a pic of the printed circuit.

72chevyLWB · 07-01-2002, 08:03 PM

and

my new 72 · 07-01-2002, 08:17 PM

They should be in series. You could also get a bare board with no cicuitryor holes in it and cut it to fit, and build your own. Not that hard. That way you could integrate an led turn signal with a split in the board, and different colored lights.

72chevyLWB · 07-01-2002, 08:22 PM

But I'm a cheap A#$ and this looks like a cheaper alternative. I have this one plus one more coming off one of our builders. I would wire up just the outside one to blink and all of them for the brake. Figure something out.

CE20934 · 07-01-2002, 08:36 PM

They should be in parallel, not series. If they were in series, they'd go from very bright to very dim since each light would eat a bit more voltage as the electricity moved down the line.

Series is like the small Christmas lights (the infamous, "If one goes out, they all go out!"). Parallel is like the big lights (the bulbs screw in). Your dash lights are in parallel.

72chevyLWB · 07-01-2002, 08:42 PM

okay, so now what

RipMeyer · 07-01-2002, 09:57 PM

series is for constant current and parallel is for constant voltage.

my new 72 · 07-01-2002, 10:00 PM

If you place resistors and small capicitors in the beginning and the end of the series like ford has done on there LED's then it keeps a constant rate of energy to all the bulbs.

CE20934 · 07-01-2002, 11:02 PM

Why? If they're in parallel, you already have constant voltage. Adding resistance is just going...

Wait a minute. Do those LEDs take a full 12V (I would think so, but then again I think in incandescent bulbs) or do they take 5V like an ECM & all its sensors? If they took 5V, I could see why resistors would help.

Benrs86 · 07-01-2002, 11:05 PM

i THINK most LEDs take 9 volts.

BubbaGreen · 07-01-2002, 11:52 PM

They are in parallel...
Most LEDs take 2~4 volts, too much voltage and they will
burn out quickly. I am not familiar with the circuit shown,
but when removing extra LEDs, for each LED removed you
can count on approx 20mA extra going to each LED left.
There may be a voltage regulator, and/or resistors mounted
on the back, ie, surface mount compontents. Most likey,
removing one or two, no problem, more than that and you
may end up with all the LED failing rather quickly depending
upon the design. Best way to determine the current draw
is to use an ammeter on the entire unit, then divide the amps
by number of LEDs. If you remove quite a few of the LEDs,
you may have to install resistors to make up to the current
flow that those LEDs provided for, or else, you'll experience
the entire unit failing to light...If you need more help, just
e-mail me offline, will be glad to help you make it work.

CE20934 · 07-02-2002, 12:12 AM

Ahhh! Makes sense now.

70 Jimmy · 07-02-2002, 09:05 AM

Yeah but they sound really cool when they blow up. Like a little firecracker!
They may actually be both series and parrallel in groups. Remember, all 12+ volts must be consumed by the components in the series portion of the curcuit (ie, 6 LEDs divided into 12 equals 2vdc each LED. 4 LEDs divided into 12 equals 3vdc). If you cut some LED's out, either eliminate the entire series (if it's one of several groups) or add a resistor to replace the drop from the LED's. Hope this helps.

07-01-2002, 08:02 PM	#1
72chevyLWB Got 20's???? Join Date: Oct 2001 Location: Aberdeen SD Posts: 1,451	LED/ electrical ? I have an LED bar from a 98 S-10 3rd brake light. Now, these lights are in series right? So can I just cut off which ones I don't need because its too tall. I am going to do 2 or 3 rows of LED's in each tail light going up and down. I just need to find out how to trim them down. Heres a pic of the printed circuit. Attached Images __________________ 99 Silverado Ex-Cab 2wd, Bagged&WhippleCharged 02 Sierra Ex-Cab 4wd 2500 HD The 72 went down the road.

07-01-2002, 08:03 PM	#2
72chevyLWB Got 20's???? Join Date: Oct 2001 Location: Aberdeen SD Posts: 1,451	and Attached Images __________________ 99 Silverado Ex-Cab 2wd, Bagged&WhippleCharged 02 Sierra Ex-Cab 4wd 2500 HD The 72 went down the road.

07-01-2002, 08:17 PM	#3
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	They should be in series. You could also get a bare board with no cicuitryor holes in it and cut it to fit, and build your own. Not that hard. That way you could integrate an led turn signal with a split in the board, and different colored lights. __________________ I'm going to Law School, wanna debate? It's good practice.

07-01-2002, 08:22 PM	#4
72chevyLWB Got 20's???? Join Date: Oct 2001 Location: Aberdeen SD Posts: 1,451	But I'm a cheap A#$ and this looks like a cheaper alternative. I have this one plus one more coming off one of our builders. I would wire up just the outside one to blink and all of them for the brake. Figure something out. __________________ 99 Silverado Ex-Cab 2wd, Bagged&WhippleCharged 02 Sierra Ex-Cab 4wd 2500 HD The 72 went down the road.

07-01-2002, 08:36 PM	#5
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	They should be in parallel, not series. If they were in series, they'd go from very bright to very dim since each light would eat a bit more voltage as the electricity moved down the line. Series is like the small Christmas lights (the infamous, "If one goes out, they all go out!"). Parallel is like the big lights (the bulbs screw in). Your dash lights are in parallel. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

07-01-2002, 08:42 PM	#6
72chevyLWB Got 20's???? Join Date: Oct 2001 Location: Aberdeen SD Posts: 1,451	okay, so now what __________________ 99 Silverado Ex-Cab 2wd, Bagged&WhippleCharged 02 Sierra Ex-Cab 4wd 2500 HD The 72 went down the road.

07-01-2002, 09:57 PM	#7
RipMeyer Registered User Join Date: Oct 2001 Location: Southern New Mexico Posts: 649	series is for constant current and parallel is for constant voltage.

07-01-2002, 10:00 PM	#8
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	If you place resistors and small capicitors in the beginning and the end of the series like ford has done on there LED's then it keeps a constant rate of energy to all the bulbs. __________________ I'm going to Law School, wanna debate? It's good practice.

07-01-2002, 11:02 PM	#9
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	Why? If they're in parallel, you already have constant voltage. Adding resistance is just going... Wait a minute. Do those LEDs take a full 12V (I would think so, but then again I think in incandescent bulbs) or do they take 5V like an ECM & all its sensors? If they took 5V, I could see why resistors would help. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

07-01-2002, 11:05 PM	#10
Benrs86 Registered User Join Date: Feb 2000 Location: Brandon, SD, USA Posts: 1,292	i THINK most LEDs take 9 volts. __________________ Brandon, SD 69 GMC 1/2 ton 2wd wide long bed with wood 3 on the tree 350 engine 4 bolt main rv cam AIM = Alphray04

07-01-2002, 11:52 PM	#11
BubbaGreen Senior Member Join Date: Mar 2001 Location: Cedar Park, TX Posts: 686	They are in parallel... Most LEDs take 2~4 volts, too much voltage and they will burn out quickly. I am not familiar with the circuit shown, but when removing extra LEDs, for each LED removed you can count on approx 20mA extra going to each LED left. There may be a voltage regulator, and/or resistors mounted on the back, ie, surface mount compontents. Most likey, removing one or two, no problem, more than that and you may end up with all the LED failing rather quickly depending upon the design. Best way to determine the current draw is to use an ammeter on the entire unit, then divide the amps by number of LEDs. If you remove quite a few of the LEDs, you may have to install resistors to make up to the current flow that those LEDs provided for, or else, you'll experience the entire unit failing to light...If you need more help, just e-mail me offline, will be glad to help you make it work. __________________ 71 Chevy C-10 SWB Fleetside RamJet-350/4L60e & Compushift/3.73Posi See it at www.prismnet.com/~grzanich

07-02-2002, 12:12 AM	#12
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	Ahhh! Makes sense now. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

07-02-2002, 09:05 AM	#13
70 Jimmy aka Crusher, Crushergmc Join Date: Mar 2000 Location: Oregon Posts: 1,834	Yeah but they sound really cool when they blow up. Like a little firecracker! They may actually be both series and parrallel in groups. Remember, all 12+ volts must be consumed by the components in the series portion of the curcuit (ie, 6 LEDs divided into 12 equals 2vdc each LED. 4 LEDs divided into 12 equals 3vdc). If you cut some LED's out, either eliminate the entire series (if it's one of several groups) or add a resistor to replace the drop from the LED's. Hope this helps. __________________ "KEEP IT DOWN!" 70 Jimmy 454 2wd 56 GMC Big Window "It's funny till someone gets hurt, then it's freakin' hilarious"

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