Author Topic: FAQ: Various LED How-To's & Info!  (Read 9398 times)

Offline pandy

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FAQ: Various LED How-To's & Info!
« on: February 22, 2006, 03:59:05 PM »;topicseen;topicseen

This is one of the topics that keeps coming back. It is another item that needs to be in a FAQ with some how-to and theory to help those troubleshooting a, usually self-induced, problem.

Changing the turn signals (blinkers) to LED probably requires modifying the dash indicator lamp circuit. Why? The dash indicator lamp is the path for the ground (earth) of the used lamps via the un-used lamps.  Confused?

If you can read schematics, the above pic tells the entire story. Stay with me a bit and read on. Then it may become clear why this is not a fast swap.

Here's the order of operation:
Assumptions - The bike is running and powered up & you decide to turn LEFT.

1) The turn signal switch (TSS) connects the light blue wire to the black wire. This applies power to the Left Front, Left Rear, and Indicator lamps. The Left Front and Rear lamps have their own ground (earth) to make them get HOT and light up. The Indicator lamp ground (earth) is made via the RIGHT front and rear lamps! You are actually warming up the Right Front and Rear lamps to light up the Indicator lamp!

2) The turn signal relay (TSR) operates and OPENS the +12V feeding the LEFT circuit. The lamps go COLD and turn off.

3) The TSR closes and the cycle continues until YOU turn off the TSS permanently opening the circuit.

4) The operation of the RIGHT side is identical in theory, but with the other components. The Left signal lamps become the ground path for the indicator lamp.

As accurately mentioned above, LEDs use far, far LESS current to illuminate than our filament lamps. A filament lamp uses AMPS. An LED uses MILLIAMPS.

This poses two problems.
1 - The TSR is designed to operate with HIGH current (AMPS). The lower requirements of the LEDs can/could cause the fast blink "feature" or no blink at all.
2 - Another possibility is all four indicators coming on at once! This has been reported here also and is evident when you look at the schematic. All 5 lamps are passing some current when blinking. 3 have enough current to light up. The other two providing ground (earth) do not.

Adding a resistor in series or parallel will not increase the current the LED uses, it will decrease the current if in series or shunt the current in parallel. Others have used resistors in a shunt path to force extra current around the LED and trick the TSR into seeing the same load. Others have removed the indicator lamp completely to eliminate the "5 LED flash" that can happen. Any resistor will have to be a very low value to draw enough current to fool the TSR. As I hope you can see, it is not a plug-and-blink operation.

Well, at least I can see it is not a simple thing.  :laugh:

How would I do this? I would design a special LED lamp that draws the same current as a filament lamp. This would require a shunt resistor path and a path for the LED inside the device (LED-lamp hybrid).

This is counter-intuitive for selecting an LED in the first place - lower current demand!

Another option is modifying the stock GS wiring to use a different TSR and a bi-directional LED for the TS indicator. The stock lamps are cheap, they work, and frankly I don't mind them. The modifications needed to make up for the basic design are a lot of trouble for the weekend wrencher (or the black tape crowd  :icon_mrgreen:).

LEDs are an attractive option IF designed for in the first place, i.e. SV650, etc. If adapted to the GS, they are forced to work in a circuit not designed for them.
« Last Edit: April 24, 2007, 04:41:15 AM by pandy »
'06 SV650s (1 past Gixxer; 3 past GS500s)
I get blamed for EVERYTHING around here!