Historical hardware setup subpage of InputTrigger/AudiTrigger - also some advanced "insider" info for the curious

For v3.0 .. v3.2:

For v3.3 shipped in 2005:

For v3.3 shipped after 2006: - done at assembly if requested in shop order note

Idea never applied: possible elmination of RPM trigger shadow from the crankhome-VR signal (also called magnetic shadow, or magnetic ghost). '''Was solved with 1k pulldown and sectrig LM1815 pin5=+5V)

An idea was to connect both the crankhome-VR and crank135-VR signal via appr 33k (best resistor value needs some experimentation and tuning with scope) to a +-700mV clamped point (fast diodes towards GND, eg with a BAV99 or 2 1n4148). The crank135-VR might need to be reversed for this to work (in the elimination direction, not to amplify the unwanted ghost signal).

The crankhome-VR polarity is fixed, of course (because LM1815 senses negative going edge). If the magnetic pulse is not near 0 or 180 degree phase, this is no big use.

Jorgen's SwCAD? simulations: two 1n4148 switch diodes connected antiparallel to each other and in series with the incomming VR signal from the TDC sensor. I have no Audi here to test it on but logic, some scope plots I have taken earlier and the CAD software say that it will totally eliminate all signals smaller then 0.5-0.6v or so while also dampening the TDC pulse with 0.5-0.6v. The TDC signal should be over 0.7v at all cranking rpms and the RPM shadow should be lower then 0.5v at most critical rpms. At higher rpm the RPM signal should be eliminated properly by the arm level logic in the LM1815. -Jörgen Karlsson

Some changes needed when compared to standard VEMS ECU:

The Audi trigger is very different compared to most other triggers and they require a few modifications. -Jörgen

  • The signal qualiy of the secondary trigger signal is very low. A 1k resistor to ground between the sensor input wire and ground improves the signal quality greatly and dampen the high frequency electrical noise and the low frequency magnetic noise from the 135 tooth trigger. -Jörgen
  • We also configure the minimum adaptive threshold for the secondary VR, there is a jumper at pin5 of the secondary VR that let you connect pin5 to VCC. After this is done the typical min threshold for arming the chip is 200mV instead of 30mV. That means that the chip will always ignore signals under these thresholds in each respective mode. With a stronger signal both modes are adaptive. -Jörgen
  • In some ecu's a resistor is populated in the R182 position, it must be shorted with a 0ohm resistor (as in recent ECU's) or with a solder bridge. -Jörgen
  • The diode circuit I mentioned in the section above is not needed to get a reliable trigger signal. -Jörgen
  • With the primary trigger we have a different problem. At high rpm the trigger frequency get extremely high. The LM1815 VR interface chip has a RC configurable output pulse. A standard ECU has R57=75k resistor and C31=1n. For Auditrigger you should use R57=33k and C31=1n which give us a pulse of around 30uS. As an example we only have 1/9000rpm*135teeth/60s=49uS between each trigger event at 9000rpm. The pulse with R57=75k would be around 70uS. -Jörgen
  • R56 and C30 create a low pass filter with a theoretical -3dB frequency of 8841Hz. In real life it's common that the capacitors are of a bit higher capacitance then specified. 8841Hz correspond to 3930rpm. This may cause concern at first but when considering that the signal amplitude on the input increase with rpm and that we clamp the input below 2v it should not be a problem. -Jörgen
  • There is no real signal quality problem with the primary trigger, but as the signal is very strong so we want to load it a bit to protect the input filter for the LM1815 and the input clamp in the LM1815, a 1k resistor should be suitable for this as well but note that it may need a higher power rating. We need to measure the signal amplitude at high rpm to know. -Jörgen