Trigger off of hole in cam gear?

[bpsims]

Trying to sort out a cam trigger. My cam gear has a very convenient hole in it that would lend itself to being detected w/o much modification. Is it possible to use a gear tooth sensor to trigger off this hole? I'd like to avoid trying to source a magnet that would fit in there for a hall sensor or adding material to make a tooth. It seems like an opposite acting gear tooth sensor would be ideal here - open when in the presence of metal and then closing when the hole appears.

[dontz125]

Don't see why not. The R6 cam sensor triggers off of a radial drilling in the cam shaft.

[24c]

Ditto... YZF1000 & FZR1000 both do this with seven holes and a bigger milled slot in the crank web, but using a VR sensor too.

I have experimented with different tooth patterns on my test rig, and using a car type Hall sensor, a drilled hole works very well.
Are you using this a a sole trigger, or to get a cam signal?
I only ask, because you could machine the sprocket to give more "teeth" if required.

Mike

[bpsims]

Thanks, this is reassuring.

24c - This is just for a cam signal.

I'm still curious as to how the signal will work. I'll be using a Cherry GS100701 sensor. Normally, the sensor would pulse on a raised piece of metal and send a signal. Using a hole as the trigger, it seems like the sensor would constantly be sending a signal and then briefly stop as the hole passes by. Can the microsquirt pick up this "inverted" pattern and use it? Also, the end of the sensor might be a too big for the little hole in the cam gear. The hole is a little smaller than a pencil's eraser. Looking at pictures of this sensor, it's impossible to tell how big of a hole is required to get the sensor to do its thing.

I also ran across someone using the rocker arm to trigger. This might be another way to go.

[dontz125]

The uS will trigger off the rising or falling edge, depending which you select.

The only way I can think of to test whether the drilling will properly trigger the sensor is to try it.

[bpsims]

Great - the rising/falling edge setting makes sense. The sensor should get here this weekend.

Thanks for your help, guys. Much appreciated.

[24c]

You could always test this trigger by making a replica disc, and chucking it a cordless drill. That way working off the bench, you get to see first hand how close, what size hole was required. Ignore that it's a cam trigger just create a different tooth pattern project, so the Microsquirt will trigger off a single tooth trigger. Later combine it with the crank set up on your engine.

You'll learn something along the way, as well as knowing that the cam trigger side of things is OK.

Mike

[bpsims]

The Cherry GS100701 sensor seems to work fine with the hole in the cam gear. I spun the cam gear up on my lathe and got a nice signal from it.
I did notice a powerup issue with the sensor where the output is the same whether it's in the presence of metal or not. It's not until the first edge detection until it gets it right. Basically validating this thread: http://www.msextra.com/forums/viewtopic ... 69&start=0 . I'm hoping this won't cause an issue

I wanted to confirm cam sensor positioning before I start any drilling. I'm using a 36-1 crank trigger wheel with the 9th tooth on the crank sensor at TDC. I was under the impression that the location of the cam sensor trigger wasn't very specific as long as it was before the tooth gap by a couple of teeth. But then I started coming across some information regarding dual spark and autotrigger that got me questioning things.


http://www.megamanual.com/seq/autotrig.htm
M-N Crank Wheel
For 2, 4, 6, 8 cylinders:
Cam synch must fall between Cam_Tooth and Tooth 1, where Cam_Tooth is defined in Fig. 4.
For 3, 5 cylinders: Cam synch must fall in missing tooth gap.
Cam_Tooth = 0

No mention of 1 cylinder here. But it looks like odd cylindered engines want the cam synch to take place in the gap.


http://www.useasydocs.com/details/dualspark.htm
c. M-N toothed wheel on input 1. The cam synch on input 2 must be placed so that it occurs during the missing teeth.

So, where's the ideal location to trigger a cam signal for a single cylinder? During the crank tooth gap? The optimal place in my valve cover get's me close to that (actually it's closer to tooth #1, but I can adjust a bit).

Thanks!

[dontz125]

I'm not familiar enough with the B&G code to comment intelligently on that, but I can say that - now that I know you're working with a single - the Extra code allows 'cam' sync of singles using the MAP sensor. No fussing with cam sensors required ...

[24c]

So, where's the ideal location to trigger a cam signal for a single cylinder? During the crank tooth gap?

It is during the crank tooth gap, as I understand it. The manual reiterates this several times for "dual spark" modes.
You've read the bit about "tying" IGN1 & IGN2 to get a sequential or wasted ignition event?

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