InputTrigger/AudiTrigger/TestLM (2005-12-27 09:30:02)

What to measure and what to think about when running secondary trigger VR on a 3.2 or 3.3

Make a report of your measurements. All pins.


Report reasonably please

If you start to write these few things systematically, it's very likely the problem is revealed in no time. Rumbling on irc you waste much time, without result. This is very important. Reports without the most basic info, or to the wrong place is useless.


Emil's board - reply after the report requirements stressed on irc

v3.2, standard, Earlier trigged by primary trigger VR in a car.

Miska's board

Magnus board (aka 944_Driver on msnordic)

The problem is that interference from the starter gear sensor is triggering the secondary LM1815 circuit too. Cranking on the starter with the plugs removed and I get about 15 Vpp from the starter gear (quite high for cranking speed) sensor and 1.5 Vpp from the crankhome sensor. The interference found in crankhome signal is about 200 mVpp. Shielded cables are used all the way from sensors to the board.

So you are sure, that

I tried to decrease the starter gear senor output by applying a 1.5 kOhm resistor in parallel with it, but that didn't do much good. The interference got smaller but not much.

Is it possible to modify the circuit around the second LM1815 chip in such a way that the interference is ignored at all engine speeds? Just connecting the U12.5 pin to VCC will probably not fix it for all rpm I am afraid since the interference will get bigger with increasing rpm.

Does anyone know how Bosch solved the problem since it works fine with the stock motronic box?