LED warning light

[ejenner]

I have a knock sensing box connected to my engine to detect knock. It's actually a Saab APC boost controller but I have just the minimum wires connected to make it detect knock. It works very well. But as I fine tune the maps more I'm feeling the need to have a dash mounted LED to flash as a warning when knock is happening.

At the moment the output wire from the Saab APC box is connected to AT3 on my M800. It swings low when knock is detected. The M800 is set to register a valid input when the voltage drops below 3.0v - any lower and the event will be out of range and not detected.

To show me when knock is detected I have a 'Status light' configured on my Motec virtual dash on my laptop. This is perfect for monitoring knock during tuning but I can't see it when I'm driving.

So I need to configure an output from the M800 that can turn on a dash mounted LED. I have a 12v LED mounted on my dash. The positive leg is connected currently to AUX6. When the engine is running the LED glows at half-brightness. Nothing I do seems to change that. Have tried reversing the polarity so the ground leg is connected to the M800 instead. Strangely this seems to produce the same response - the LED glows dimly.

Now it wouldn't be so much of a problem if it always glowed like this and fully illuminated when active. But it does not do this either! Have also tried connecting the positive leg of the LED to 12v source and the ground leg to the motec. That gives me a fully illuminated LED.

So a bit stuck with this quite simple task. Any help much appreciated.

[RossB]

Without seeing your configuration it is hard to say why this isn't working. What function are you using on your output? Are you using the Status output?

To stop the LED from glowing all the time wire one side of the LED to your output and the other side to earth or 0V. In the parameters for the output set the Logic Polarity to 1 and the Output Mode to 2.