cheap AFR indicator - build one for yourself

[arekkocowicz]

I designed small circuit which "steals" signal from lambda sensor and shows if engine runs on lean, stoichiometric or rich mixture. I documented circuit, and PCB project, and soon I will write about two of these circuits which are already mounted in cars.
I would like to hear your opinion about this circuit, I posted a note about it here Notatki: Lambda sensor based Air-fuel ratio indicator [AFR] 1 hope you will enjoy reading. I also hope I didn't make to much spelling mistakes - I am not native english speaker.

[Quezacotl]

Nice
I made same type of circuit, with LM3914, with 20 LEDs, displaying 0,1-1,1 voltages. The circuit can be found all over the net. I have'nt installed it yet though, just calibrated.

[arekkocowicz]

I think I saw your circuit, I even thought about building it, but I think It's easier to find place and drill a hole for one LED than for 20 LED

[Quezacotl]

Yea that's true. I came to this solution because i have a perfect place for 20 LEDs(they are 2x5 square LEDs in tight row)

[Quezacotl]

How does your circuit work? Or did you install it yet?

My circuit bounces a lot from about 0,4V to over 1,1V, most of the time it's rich. Damn narrow-range lambda

[arekkocowicz]

Yes, I've installed it in two cars. I supply my circuits from lambda sensor heater and I noticed that in Fiat heater is continuously on but in Opel heater is supplied with low frequency PWM. I will try to film it and upload somehow. There is also obvious problem that cold lambda sensor doesn't work so first couple of second after engine start it shows constant voltage which in Opel is interpreted as Rich (that's logic, right?) but if Fiat it shows voltage corresponding to lean mixture