Capturing Tachometer signal

[randomvalue]

Hi,
Im wondering on how I should go about capturing a tach signal for use with a Pic micro-controller. I have thought about just rectifying the signal from a pulsed dc (basicaly ac) signal into dc using a diode bridge and just sampling the signal using the on-board adc. Im wondering if this is the correct way or if there is a better way to do this.

My goal is to use the captured value to control a software pwm for a servo.

any input would help

thanks,

Random

 

[florinasdragalas]

More data please
What kind of tachometer?
What kind of servo? position or speed?
I used a washing machine motor with AC tacho for speed servo ; controling high speed in 5000 -13000 rpm range with uc3843 ,no micro.

 

[randomvalue]

Sorry, the tach signal comes from an engine management module. I plan to use a position servo as a kind of govoner. Basicaly I need to hold the engine speed constant over a varying load. The current govoner uses oil pressure to move an arm to control the throttle, this is adequate if the load is fairly constant. unfortunately this is not true in my experiment.

What i have been trying to do so far is to make a servo follow the adc. so far its not working right, but that could be because the code is still sloppy. I do not write in C yet, still tinkering in assembler. And the costs out weigh the benifits that basic provides.

 

[florinasdragalas]

Sorry, the tach signal comes from an engine management module...

This secret "...signal..." is TTL ,CMOS,AC,DC,quadrature,absolute number,sine/cosine or what ? 8O
( I don't dare to ask what's engine management module... )

I plan to use a position servo as a kind of govoner. Basicaly I need to hold the engine speed constant over a varying load. .

"...position servo..." like in RC Servo ?!?. :???:

The current govoner uses oil pressure to move an arm to control the throttle.

Please give us more data ... pretty please ...

Sorry couldn't resist ;-)