Doubling the pusle count

[Acetronics2]

Hi, Darrel

Your job is nice ...and I do appreciate !!!

Just understand it is over the requirements ...

But excellent example for further general development !!!

Alain

[Darrel Taylor]

Is it me? Or is everyone going nut's around me.

I got a teddy bear to throw here....
<br>

[mister_e]

don't worry... i feel of some jealousy 'round

[malc-c]

Is it me? Or is everyone going nut's around me.

I got a teddy bear to throw here....
<br>

LOL - (seems my comment stuck )

Well I apreciate your help Darrel.

I have a 12F675 to hand, and I'll compile and burn the HEX to it and post it to my mate so he can try it. What would be the best way to interface the PIC to the signal, assuming it output is at 12v battery levels.

[malc-c]

Darrel,

I've just received a reply from my mate

The pulses appear to be 0-12-0 "square" wave, but not 50/50 duty cycle. the 12 volt pulse is much less than the 0 volt. I've found that a similar unit off a Ford uses a hall effect transistor and a multipole magnet, very similar to a heli throttle govenor.

Frequency...difficult right now to get you an accurate figure for the maximum..minimum is easy, it's 0....LOL. I can't imagine it would be more than 1 khz maximum on the unit I have.

Does this help to determin the adjustments for the code

[mister_e]

o.k. ONCE again

which car model, brand, year?

[malc-c]

o.k. ONCE again

which car model, brand, year?

Probably not going to mean much to you.

Make and Model: Vauxhall Corsa
Year: ? no idea - will ask him.

All I had to go on was:

My wife Jenny has a Vauxhall Corsa that had just a cable driven speedo. I've gotten hold of an insrtumanet cluster that has tacho and speedo, but the speedo isn't cable, it's electrical. The tach works fine, but the rotary encoder I've picked up (which is supposed to be the right one) is giving only half the number of pulses required by the speedo, i.e. the speedo is reading half the actual speed.
The question I have is....."Is there a simple way to double the number of pulses to the speedo...like a frequency doubling circuit" ??

I believe the unit I have works optically...disc with 10 light dark changes per rev. The easy answer would be to put a disc in the unit with twice the number of segments, but it's not able to be disassembled easily.

[mister_e]

Maybe you didn't know it alrady but, i've been a car accessoiries installer (alarm, car starter, radio, gps, etc etc ) for over 12 years and i still do some custom car modification here and there.

Why i asked, is because most cruise control brand have their own application list and hints. Even on some VSS generated cable, some cars may have another source for an optional Cruise control or else. And you was right... i never see any opel/vauxhall here... only few picture here and there over the web.

Anyways, without knowing the exact frequency range, Darrel's example have to work within it's range... no doubt on it!

To interface.. a simple NPN or PNP or simple OP-AMP would do the job pretty well. I don't think 12V amplitude is really needed... maybe 5Volts could work... with a simple resistor in serie.

Hey.. you didn't SIMed it this time ?