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Spark revcounter signal for pic

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lele_75

New Member
Hi ,
i'm studying a solution to build a digital tachometer / Revolution counter with a pic16f877 for my gokart.

i'm a litle bit confused about the input signal: how can i pick up signal for pic?

i've considered two possibility:
1) i can pick up the spark signal form the engine with an inductive sensor (i wire near the spark cable) but in this case i ask you how this signal can be applied to pic? i immagine this is a very noised signal: is there any circuit for filtering / adapt it?

2) i can measure the rpm of the weel with an hall effect sensor but also in this case i need a circuit schema for adapt the sensor output to the pic (as far as i know many hall sensor output signal range is from 2,5 to 5 volt and so it's not ok for a square wave pic cunter input)


thankyou all
 

be80be

Well-Known Member
I would get the signal from the points it only about 12volts some are even 6volts or even better you could use a magnet switch set it so the flywheel trips it and your trigger voltage can be whatever you want like a nice 5 volts.
The part they use for alarms would work easy. Then just count how many time it closes a minute.
 

lele_75

New Member
thankyou,
no need of debounce circuit in case of mechanical contact? and what about robustness?

thankyou
 

binzer

Member
Hi ,
i'm studying a solution to build a digital tachometer / Revolution counter with a pic16f877 for my gokart.

i'm a litle bit confused about the input signal: how can i pick up signal for pic?

i've considered two possibility:
1) i can pick up the spark signal form the engine with an inductive sensor (i wire near the spark cable) but in this case i ask you how this signal can be applied to pic? i immagine this is a very noised signal: is there any circuit for filtering / adapt it?

2) i can measure the rpm of the weel with an hall effect sensor but also in this case i need a circuit schema for adapt the sensor output to the pic (as far as i know many hall sensor output signal range is from 2,5 to 5 volt and so it's not ok for a square wave pic cunter input)


thankyou all
What voltages do you have on your machine?
If you have at least 12v you could get a 3 wire prox switch, with a bracket on the end of the engine you could sense the key on the engine shaft.
Mike..
 

lele_75

New Member
thankyou, let me understand better:

when you say "magnetic sensor" or "prox sensor", are you speaking about hall effect sensor or reed sensor?

Michele
 

binzer

Member
thankyou, let me understand better:

when you say "magnetic sensor" or "prox sensor", are you speaking about hall effect sensor or reed sensor?

Michele
Neither, a 'prox' (proximity) device senses when a object is in it's sensing range, you do not need a magnet like a reed or hall effect sensor, thats why I said you could just use the key in the motor shaft. Try a google. These devices come in a bunch of sizes, they get used where I work on many machines along with reed and hall switches.

mike.
 
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