How to modify turn-signal flasher to work with LED bulbs

[hcychang]

Dear all

I want to install some LED turn signal bulbs and lights but the flasher will flash twice as quick because of the burnt-bulb detector.

I have taken the flasher apart and tried all the tricks on the book to isolate each pin on the IC and changed the timing resistor without avail. I do not want to put in load resistor on the bulb end to fool the detection circuit.

Can anyone help me on this one if I want to modify/cut off the detection circuit please?

Many thanks.

[JSM1284]

Purchase a special flasher, or load limiting resister from Superbrightleds.com

[workerant]

Y don't U want to put in the load resister? Maybe the power regulator for the LED will help simulate this load.

[hcychang]

Originally Posted by TTM77

Y don't U want to put in the load resister? Maybe the power regulator for the LED will help simulate this load.

Hi, I don't want to put a resistor in because it will need to consume a large power, which (1) generate a lot of heat and (2) defeats one of the purposes of using LEDs to reduce power consumption.

[JSM1284]

The power consumption between a standard filement bulb, and an LED is extremely minimal. Not even worth it if thats the only reason you switched.

[JSM1284]

You need this:

ELECTRONIC LED FLASHERS

We now offer 2-Pin and 3-Pin (1/4 inch spade lug type) LED compatible Flasher Units in this category
You should definitely use one of these instead of Load Resistors if we have one to fit your vehicle
They operate at the correct flash rate with LED or standard filament bulbs
10~15 Volts DC - Flash Rate: 80 per minute

Note that some of these flashers operate silently, they do not make the familiar clicking sound when operating. One solution is to connect a common automotive relay to the output along with your LED bulbs
Also note that these flashers do not replace all flasher units. Before you order, please see the pin outs of our flashers in the "more info" page below and compare with the one you are replacing. Click the part numbers for complete spec sheets. You can usually find your flasher pin out printed right on your flasher. Failure to check this and installation in an incompatible vehicle can blow your fuse, destroy the flasher and void the flasher warranty

[hcychang]

Well, I finally have it sorted.

After reading a lot of articules on the Internet and applied my long-lost knowledge on electronics, I have figured out that the chip is detecting certain voltage drop across the bulbs (which would now be different because of the low power consumption of the LEDs). I have therefore isolated the detection pin and wired it to a variable resistor taking an adjustable voltage between 12V and the ground, and slowly turning the variable resistor until chip detects the expected voltage drop, and, bingo!

I used a 500K ohm variable resistor so the current drain is minimal and quite a lot less than even the LEDs, thus maintaining my power-saving purpose. This also saves me from buying the special purpose flasher. It is working in the simulated environment (no load, no bulb, no LED) and I will be testing the flasher over the weekend with some home-made LED bulbs. I expect it will just work beautifuly because the variable resistor is now fooling the circuit and it won't matter what I do with the bulb ends.

[hcychang]

Originally Posted by JSM1284

The power consumption between a standard filement bulb, and an LED is extremely minimal. Not even worth it if thats the only reason you switched.

I beg to differ. The standard indicator bulb at the back of the Camry is 8W, drawing 0.66A from the 12V battery. My home-made super-bright LEDs of 9 LEDs is drawing less than 0.1A (1.2W) so there is a huge difference in power consumption in my case.

It's not my main reason of switching over but I'd still like to think that it is also helping to save the power.

[JSM1284]

What do you need the power savings for?

[hcychang]

Originally Posted by JSM1284

What do you need the power savings for?

So that I know I can leave some of these lights on (when the engine is not runngin) longer than normal without the fear that they would drain my battery.

[TRD VVTi]

Originally Posted by hcychang

So that I know I can leave some of these lights on (when the engine is not runngin) longer than normal without the fear that they would drain my battery.

[JSM1284]

[geoff5093]

Originally Posted by TRD VVTi

It's true, probably not so much with the flashers but if you have your 4 ways and taillights on for a few hours, you notice how much harder it is for the battery to turn over. I had just my 4 ways on for about 4-5 hours and I had some serious trouble trying to start my car.

[Tobeit]

...begs the question: Why would you do that in the first place?