C h a z

Couldn't get the thing to work at all. I was trying to build the bar (10 led) version. I just can't seem to get it to work. I started by using Scotts diagram and then realised that this was for 5 single leds, but i thought that I would be able to wire up just half of the bar. Very pi55ed off with myself. I wish I had never bothered. (storms off out of the room)

john banks

If you want to get it to work, please advise what voltages you see at each pin relative to ground.

C h a z

Calmed down now. Rewired the whole thing on a new bit of board. I am assuming the wire that I'm using at the ECU is the correct one. It seems to wander about around 0-700mV during idle and then float about the 800's at WOT. When I connect the battery now the first LED is allways lit. Voltages at the pin outs seemed to vary. However I have not measured them on the second build. I could only get this first LED to light. Thanks in advance for any further help.

john banks

The behaviour you describe of the voltage is as expected from a lambda sensor.

You need to make sure that the reference pins (4 and 6) on the LM3914N are set correctly. What voltage do they have relative to ground.

C h a z

700mV and 900mV relative to the - on the 9V batt
Output are as follows:


[Edited by C h a z - 3/24/2002 8:46:00 PM]

C h a z

Seem to have made a little progress. I am using the layout on the breadboard as described by scott, but with the 10 bar led display. So it looks the same as the diagram except that pins 1& 10-18 are connected directly to the led display. The far pins on the display are connected togeter to pin 3. On testing in the car I got an occasional flicker right across the display when at idle.(note to self: do not do this in the garage again, nearly gassed myself.) However when testing with the voltmeter I accidently connected pin4 to ground, the display went bananas! Flicking up and down all the time. I will try the AFR tomorrow at WOT to see what it does.

john banks

It should work fine. Note it needs to warm up for a few minute at idle before you get Knight Rider effects, but if you are lighting some LEDs, since your references are corret it should be working fine!

C h a z

I must be doing something wrong. I notice on Scotts diagram that one of the VR's pins is not connected to anything. If I ground this to the car I get the knight rider effect. I will try it later to see if it gives a proper reading at WOT. PS it's my birthday today!

john banks

Happy birthday!

C h a z

I tried it and it works! How did I manage to miss this extra earth that was required? Seems odd that when I earth it to the 9V batt it does not work, but when I earth it to the car it does. I wonder if the whole thing will still work when I run it of the car 12V supply, ie when it is using the same earth as the rest of the circuit.

john banks

The 9V battery earth would need to be tied to the vehicle ground for it to work.