What kind of protection have the rpm input pin?
Can I put on signal from the ignition coil primary side, or just 0-12v rpm signal from ecu or from ignition module?
Thanks
I'm not sure about the protection, never having seen the schematics for the gauge.
As a matter of course I would use a Zener diode to block any spikes from the ignition coil.
The webshop 18V unidirectional transient diode will be good? How put am I into the circuit?
I think a plain 18v Zener would be best - mounted with the stripe facing the coil
Coil(-) -------|<----- RPM input
Thanx
I have a bit different problem about rpm input, but I thought I won't start a new thread for it. The problem is that the rpm signal is very bumpy at both Megatune and in the gauge. I took the rpm signal form the coil directly to pin 10 on the 15 pin connector. But on idle the rpm gauge jumps a great deal (from 500-2000rpm, occasionally higer and lower too). It's jumping while cruising too.
That's how the rpm signal shows in the logviewer.
(http://i313.photobucket.com/albums/ll373/kristjanl/log.jpg)
What could be causing this problem? I have the RPM settings set to 8 (4 teeth per camrot, stock distributar hall sensor on mk2 golf) teeth and the multiplier is 229. I don't know what firmware is on the gauge, it's borrowed from a friend.
Edit: My stock tacho is working in perfect order from the same source.
Anybody?? Got the multimeter and measerd the values from pin 10 (RPM input) and 11 (RPM reference). The RPM input measures around 12.2V and the RPM reference 2.80-2.87V. It's a cheap multimeter so there might be some variations in the measurements. AFAIK the 2.8V in the reference pin is ok and no pull-up nor pull-down resistor is needed. Why is the RPM reading so bumpy then?
Take the signal to the gauge from cable to original tacho. I had almoust the same problem, I taked the signal directly from RMP sensor and the signal was jumpy, now I connected it to the cable from ECU to tacho and the reading is almoust OK (it has some random spikes, but I have not seen anybody finding cure for that).
Well, I don't have an ecu and I have already tried to take the signal from the tacho, but it has the same problem because it's the same signal. I quess I'll just have to live without the tacho reading.
Tnx for your reply though.