Hi All

I'm using the K3 version of the Emerald ECU and three switchable maps. The switching for this is as shown below. I'd like to have a tri colour LED to indcate which map is currently enabled.

Anybody got any ideas on how to do this simply? This should be simple but I must be missing something!

Regards

Wyn
Rescued attachment switchable.jpg

There is not way to do it passively, i.e. just the LED and a few resistors, because the amount of current required to light an LED would significantly load the 1k pullup in the ECU (which could cause it to think the wrong map is selected).

However it's certainly doable with relative simplicity and at low cost, using comparators. I'll post a circuit if you would like to have a go.

Hi Mike

If the circuit is relatively simple, I'd have a go - I can solder and there's a local Maplins!

Thanks

Wyn

quote:

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Originally posted by robocog
..unless the 3 way switch you use can be stacked (like wafer jobbies) or has another set of contacts?

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i think this will work, please if there is some problems do let me know, i am still on the noob stage.....




the negative to the comparators is output from the switch and goign to the ecu

[Edited on 17/11/07 by ghuncha]

[Edited on 17/11/07 by ghuncha]

Thanks Guys

The two way, double pole, cenrtre off switch sounds like the option!

ghuncha - I wouldn't have a clue if your circuit worked! Thanks for the efforts though!

Regards

Wyn

Although how do I get a two position switch to operate a three colour LED?

When you say a three colour LED, what I had in mind was a "bicolour" LED that physically contains two LED chips. By driving either one, or both chips together you can get three colours. This makes the wiring very simple indeed.




I made a very simmilar circuit to ghuncha's but using a bicolour LED (only two comparators/one chip) if you still want it.

This is how you would drive a true Tricolour LED from a two position (center off) switch. This relies on the differing forward voltages (Vf) of the LEDs. Putting an LED with a lower Vf voltage in parallel with one with a higher Vf will turn off the one with the higher Vf.

Typical the Vf's of a tricolour package are:
Blue 3.3v
Green 3.3v
Red 2.0v

As you can see the green and blue LEDs in tricolour packages have very similar foward voltages which would make this scheme fail. To work around this problem we use an extra diode (1N4148 or 1N4001 etc will be fine) to increase the Vf of one LED by around 0.6 volts.

MikeRJ

I used your simple option on a bicolour LED - works a treat! Photos of the dash/wiring to follow soon.

Thanks!!!!

Glad it worked ok for you!

And here it is!