New v3.8 does not see trigger signals

[SPatrickB]

I changed the resistor but still no signal which I kind of expected since I should have seen at least some sort of signal with the original resistor.
I'm at a loss as what to do next.

[Kamuto]

have you soldered solder joint near lm1815?

[SPatrickB]

Yes, I had soldered SJ6.

[SPatrickB]

This has popped up on VEMS.hu about v3.8 changes:

Input-trigger circuits unchanged (input-trigger circuits component layout same as v3.6). By default primary trigger VR pullup resistor slightly weaker than before: R30=27k (not 18k) which allows signal detection for those VR sensors that have high resistance and low input signal (an otherwise unfortunate combination). Easy to apply stronger pullup when needed (eg a 47k pullup resistor to +5V: internally or externally), eg. for strong, but somewhat noisy VR signal.

The more I read this, the less it makes sense.  It suggests increasing resistance from 18K to 27K to weaken pullup, which seems correct. But then it say to increase resistance more to 47K for stronger pullup. I don't get it. Instead, decreasing to perhaps 4.7K would make the pullup stronger, IMO, right? 

[fphil]

You may have look to the LM1815 datasheet. I understand that the chip operates depending on the input peak to peak levels and thus on the mean value of the signal as given by the voltage divider R30 | R37 // internal sensor resistance.
For the signal detection problem, you may need a (cheap) scope to solve it (I use bitscope)
Philippe

[mattias]

It suggests increasing resistance from 18K to 27K to weaken pullup, which seems correct. But then it say to increase resistance more to 47K for stronger pullup. I don't get it. Instead, decreasing to perhaps 4.7K would make the pullup stronger, IMO, right?

It doesn't say replace 27K, it says add 47K.
If there is already 27K, adding 47K in in parallel makes 27||47 = 17 K = stronger current = stronger pull-up.

[SPatrickB]

OK, I swapped out the 75K I had put in for a 2.7K to give a combined 12.7K (R30 + R56 in series). Still no signal.

[SPatrickB]

You may have look to the LM1815 datasheet. I understand that the chip operates depending on the input peak to peak levels and thus on the mean value of the signal as given by the voltage divider R30 | R37 // internal sensor resistance.

On both my boards R37 is not populated so there is no voltage dividing happening.

[SPatrickB]

Discovered that VCC for LM1815 is 1.4V, not 5.x.  VEMS.hu said that P259 could be pulling it down but I have not used P259 for anything on this new v3.8 board.
What else could cause this?

[Kamuto]

Discovered that VCC for LM1815 is 1.4V, not 5.x.  VEMS.hu said that P259 could be pulling it down but I have not used P259 for anything on this new v3.8 board.
What else could cause this?

p259 will be dead so remove it and it will start working, or cut p259 power supply leg off

[SPatrickB]

Removed P259 and now nothing works! I have a spare so I will replace it.

[VEMS]

Hello SPatrickB,

If nothing works after removing the p259 then you have found the root cause of your problem, GND connections. Do not replace the p259 before checking all GND's i suspect you do not have GND connected on ec36-pin26 and/or the power grounds available on ec36-pin5/21/22/32 the GND's are not mutually exclusive ALL need to be connected.

If confirmed this is also the reason the p259 broke in the first place.

For suggested wiring of your grounds please follow this diagram as guideline:



Best regards, Dave

[SPatrickB]

Right on. I don't know how and I'm not going to pull the loom out and then apart to find out; but somehow sensor ground was no longer connected to ground, only the power grounds were connected. 
It's worth noting that I had used the old ground design with the single 20mm long wire between the two. ...Single point of failure....never a good thing in any design.

It's also interesting to note that v3.6 kept running, sans killing P259 and having other weird problems.
v3.8 would not even run the fuel priming on power up but I am now shocked at how quickly it fires when cranking. 

I'm looking forward to driving and more tuning as it seems a whole different animal now.