hi all,
My triggering set-up is 3 2 wire sensors. (single tooth wheel, 6 tooth wheel and 24 tooth wheel)
I am assuming that only 2 wires means they are all VR sensors.
As my vems has only 1 VR chip at the moment and i want to get her running on vems. Am i right in thinking that the 6 tooth wheel is enough for ign and batch fueling and that i'll need the single tooth input for cam sync?
The outputs are like this:
(http://img.photobucket.com/albums/v417/monty_man/vems/positionsensors.jpg)
Looking at that cam sync signal (dark blue) I'd say that you're going to have problems using it, because the voltage oscillation between triggers is too large and will trigger the LM1815 chip. The chip activates at 120mV and triggers when the voltage falls below 0v - that signal will cause regular and irregular trigger problems.
Are these distributors readily available cheaply?
Rob
My inital thought on the signal issue was to pair the engine speed and cam sync (same electronic package) to give a wider peek for the signal of cyl1 so i could get engine position from one sensor.
you would need a whole head, as the only sensor in the distributor is the 6 tooth one, the other 2 are on the cam wheel at the other end of the cam shaft. but i do have a set of sensors and a head off the car if it needed to be play'd with.
In the first instance I think we need to look at getting a clean signal from the distributor
then move onto a syncing pulse after that.
ok the green trace is the signal from the distributor, that does not look to bad to me.
Yes, and if you look at the way the trace trails off it looks as if it will work well with the VR sensor chip that we use.
Did you make that scope trace? If so then we can start doing some experiments with pull-down resistors to see if we can kill that oscillation.
Rob
no it was one i found on the rover v6 yahoo group. however i'll take my scope to work tomorrow and see if the signals are the same. i was thinking of a diac to remove the ripple in the cam sync.
Interesting, can you get a Diac that breaks down as low as 1V?
If you're up for playing you may find that you can condition the signal to give a pulse that the hall sensor will be happy to trigger from.
well I could use 2 normal diodes, that would give 0.7v brake down.
what would the hall signal need to look like?
Quote from: jago on April 18, 2008, 10:28:36 AM
well I could use 2 normal diodes, that would give 0.7v brake down.
what would the hall signal need to look like?
The hall tends to be a 5v or 12v square wave. We have a Zener that clamps the voltage internally.
I'm going to start doing something along these lines myself as I have a Toyota 4A-GE distributor which is effectively the same sort of idea as your 6 tooth trigger (it has 4) and a 24 tooth.
Are you talking about using the diodes:
Signal --->|---->|---- Sensor
Because it might be possible then to use a transistor and a zener to get something like the hall output.
But it might work without.
i see, i think i could just use the diodes to make the 0v and the zenner to make it 5v. would be almost square.
i was thinking of: maybe the 2 1n4007's in "resc1"
signal ---->|-------sensor
\--|<--/
That would keep the signal AC, which is not a bad thing, for some reason I was thinking of using the diode to clamp low voltage AC signal and block the negative voltage.
I've been talking to Jorgen and he reckons that none of this diode stuff will work.
The problem is that the polarities are wrong - the pulse needs to go positive before it goes negative.
Our hope is that the bloke who scoped that used the + probe on the common ground or mixed up the signals somehow.
Can you scope the output making sure that you get the ground spot on?
How many wires are there on the 6 output signal? (Dizzy I think it is)
Rob
i'll measure both lines for the dist, as neither are ground. i'll have to ground out one of them for the vems, i've made a brake out for all 3 sensors with a seperate ground so i can get any info needed. I'm not sure how i copy the scope to the pc so i'll just be able to say if the graphs are right or not.
all the sensors are 2 wire ones, and none of them have ground. here's the circuit showing them.
(http://img.photobucket.com/albums/v417/monty_man/vems/positionsensorsdiag.jpg)
right, i got the same waveform as the orignal picture, except the ripple in the blue trace (i got none) however the peeks and troughs are same. the intresting thing is that auto data states the 1 line has the trace and the other has the reverse, however when i measured them all 3 had a signal and earth. however, i was thinking that they could have got the data by unplugging the sensors, so my plan tomorrow is to unplug the sensors and earth the other wire and see if get the peek then the trough.
oh and is this only for the sync? or the main trigger as well? as that is also low then high.
right i've been playing with help from my dad. if we reverse the wires we get a peek the trough. he had a look at the pcb i have from the donor car, and one of the signal wires is earthed as soon as it gets to the oem ecu.
The signal is put through some diodes, zeners and resisters. to make what would resembe a sqaure ish wave, so i'm just guessing that it was pot luck that got them wired that way as it would seam to only use half of the wave.
this is the same for the 6 tooth signal, but i could not start the car with it unpluged. so only had pcb to look at.
QuoteThe signal is put through some diodes, zeners and resisters. to make what would resembe a sqaure ish wave, so i'm just guessing that it was pot luck that got them wired that way as it would seam to only use half of the wave.
That bit sounds a bit like the conditioning circuit that you had me thinking about.
But if you can get the peak then the trough then you're laughing - and should be able to use these sensors quite happily.
I have little doubt that you'll be needing to use a few pull down resistors to clamp the noise that you'll inevitably get.
Rob
yeah i may well do, i was going to use the scope on the lines at the vems once it's running on the 6 tooth wheel next week some time.
i have finaly got the the time to try the vems in the car. i have decided to post here as i have no rpm on the log i've made and my igniter (oe) went pop :(
My primary trigger is a 6 tooth wheel in the distrobutor so i assume i just need a spark every tdc. i have also set my injection to alt batch fire as i dont yet have the 2nd trigger input chip.
log:
http://www.box.net/shared/fvb7nngo4g (http://www.box.net/shared/fvb7nngo4g)
trigger settings
(http://img.photobucket.com/albums/v417/monty_man/vems/primarytrigger.jpg)
First off I'd try and use the 24 tooth primary trigger and get a sustained RPM reading.
Use 1.1.18: http://www.vems.co.uk/VEMSTech/VemsMT1.1.18Good.zip
Type: coil
Filering: disabled (this does not mean it filters the signal, but means it uses the angular width of tooth settings)
All other options disabled
Number of teeth on wheel: 24
Trigger tooth:1
Next trigger tooth: 4
Crank min period: 640
Make sure that your cam sync is disabled.