Yes, yet another oxygen sensor meter based on the LM3914 chip. In its current incarnation, it drives two 10 LED bargraph displays.
The following notes were recently posted to the quattro mailing list:
The displays could be mounted on the back of the board if desired, but they stand well clear of the other components.
It has 10 red LEDs for lean and 10 green LEDs for rich. You could mount discrete LEDs instead and use whatever colors you like. I'm not going to do remote displays this time - the new board isn't much different in size to the old remote board. It's approx 1.5 x 2.5".
Note that it's really only a volt meter that reads 0 to 1V, so you could use it for other things, for example battery voltage or a boost meter if you use an appropriate voltage divider on the input.
Grounding is important. It is best to ground the meter at the engine (intake manifold is fine). There tends to be a small voltage between the ECU ground and the manifold, so picking up the ground at the ECU isn't a good idea in my experience.
It would be nice if both displays had the same background color.
No pretty box - in fact, no box at all.
It's 2.5" wide... getting it down to 2" so is a challenge,
so don't count on there being one available that will fit in
a 2" guage in the near future.
If anyone wants more information, let me know. If you are interested in the chips used, look up LM3914 on the National Semiconductor web site. The schematic is available for appropriate bribes (beer/latte).
See Charlie Springer's O2 sensor display for another O2 sensor meter which has some nicer features - brightness control and an enclosure.
A PIC based duty cycle meter (this picture is missing the PIC though). This one was set up for the displays to be mounted remotely, though they can be mounted on the back of the board. The displays are just stuck in some anti-static foam here to keep them upright. Normally, they would be plugged into the end of the cable that goes off to the right. These displays will fit in an Audi 5000 switch blank with some creative use of some drills and an X-acto knife.
This was originally designed for the frequency valve used on the Bosch CIS K-lambda system used on the 10V Audi turbo cars, though it can be used for the wastegate frequency valve too.With slight modifications (and pulling signals from the inside of the MAC11 ECU), it is possible to display ignition timing with this board!
At the moment, the specs are as follows:
Inputs
3 thermocouple inputs, two scaled 0-500C, one 0-1000C
O2 voltage
Coolant sensor voltage
Battery voltage
Ignition timing/RPM
CIS potentiometer (or any other 0-5V signal)
MAP
Acceleration (using ADXL05, one axis)
2 duty cycles
Knock indicator
Outputs correspond to the inputs - ignition timing is per cylinder with a global indicator to indicate that timing is being retarded due to knock (requires a code change in the MAC11, haven't worked out how to do it in the MAC14 yet due to lack of space CPU IO lines). Everything just fits in the 40x2 LCD! It also dumps at 9600 baud to RS-232 serial (9 pin connector, a straight thru 9 pin M-F cable works to a laptop). Format is the same as the LCD except all the data fits on one line. Refresh rate is 10 per second.
The LCD is a generic 2 lines of 40 characters, 14 pin connector. I found some fairly large units for $15 each, green LED backlight.
The ignition timing requires wiring into the MAC11/14 to pick up the RPM and timing reference signals after signal conditioning. I have wired a couple of ECUs using a 15-pin D connector. The MAC14 has been done the same way.
Copyright © 1999-2001, Orin Eman, Revised December 19th, 2001.