gearwheel encoding

Stuart Woolford stuartw at kcbbs.gen.nz
Tue Feb 11 04:20:32 GMT 1997


On Mon, 03 Feb 1997 21:08:09 -0800 (PST), khearn at scuacc.scu.edu wrote:

>
>I seem to recall some discussion on gearwheel encoding some time
>ago, and I'm sorry for bringing it up again but...
>
>I want to put a 60 tooth wheel (with 2 missing) on the crank shaft of
>a motorcycle engine that goes up to 12000 rpm.  My problem is this, I
>don't know what the min. diameter of the wheel should be.  At 3deg. per tooth
>edge, the tooth length gets quite small as the diameter goes down.  

the size of the wheel has no effect.

at 12000rpm, and 60 teeth, you have a fixed time per tooch at and diameter.
the wheel just gets heavier but easier to make accuratly as it gets larger.

if you want slower, you must reduce the number of teeth (or the RPM ;)

>I am using a Siemens hall effect IC to pick up the pulses, which I estimate
>will be fast enough at static speeds.  However, at hard acceleration or 
>deceleration, I assume that there will be more opportunity to miss teeth 
>or add more, if the teeth are very small.

nope, at higher RPM the job gets harder, it does not really care about accel/decel.

>I'm not sure if this will actually be a problem with these sensors.
>There isn't much info on the data sheets that says how small of a 
>ferromagnetic chunck can pass and still be detected...it does say that the 
>frequency is 20MHz. 
>
>Any input would be greatly appreciated.

give it a try, use an osciliscope to watch the output, and just run it up until you see the
waveform faltering. possibly use a high-speed drill or some other machinery to test the
setup on, rather than the bike.. thereever you can get a stable 12000+RPM.
I would test to 15 if you want to go to 12, just paranoia.

----------------------------------------------------------------------
Stuart Woolford, stuartw at kcbbs.gen.nz

               >>>>In VI Where Available<<<<
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