Reading engine spark pulses for RPM measurment

[tremblaylaroue]

Hi,
I've done a digital tachometer using a PIC16F877 and an Hall effect sensor wich "sense" a small magnet attached to the engine shaft but I need to make it more "universal".
This tacho. is gonna be used with small gasoline engines wich don't have primary ignition coil signal available. What I'd like to use is to wrap a piece of insulated wire around the spark plug wire to make some kind of induction pickup. Easy and will work with any motor...

The problem is that I don't know how to filter this noisy signal to have some nice pulses for the PIC micro...

Any help will be apreciated !

Dany

 

[IanP]

You may try to put a low-pass filter (L-C) to filter out all HF noise and then a Schmitt Trigger gate or a monostabile to form nice pulses from what is left after LPF ..
Regards,
IanP

 

[david90]

Hi,
I've done a digital tachometer using a PIC16F877 and an Hall effect sensor wich "sense" a small magnet attached to the engine shaft but I need to make it more "universal".
This tacho. is gonna be used with small gasoline engines wich don't have primary ignition coil signal available. What I'd like to use is to wrap a piece of insulated wire around the spark plug wire to make some kind of induction pickup. Easy and will work with any motor...

The problem is that I don't know how to filter this noisy signal to have some nice pulses for the PIC micro...

Any help will be apreciated !

Dany

Is it possible for me to have your circuit? I have been wanting to build a tach for a while now.

 

[tremblaylaroue]

David90,
The code is written in Proton PICBASIC and mostly in French (my first language).
Also RPM measurment is only a part of the software, in fact it's a data aquisition system for an inertia dyno and I didn't have time yet to draw the schematic on some kind of software.
.
If you're not in a hurry, I will eventually translate it in english end draw the shematic, I could post it then...

Dany

Added after 5 minutes:

Ianp,
Thank you for your suggestion, but I'm a kind of newbie in analog circuits, do you have an idea of the components I should use or any link to a working design?
Regards,
Dany

 

[ridelperez34]

Hi trem, did you finished to translate your project in english? i also need your circuit in building tacho. hope you will post you project. Thanks!

Ridel

 

[dark shadow]

hi there
can i get ur cicuit drawings as well as ur program
i also wanted to do a tach using the 16f

cheeerssss

 

[enzo84]

David90,
The code is written in Proton PICBASIC and mostly in French (my first language).
Also RPM measurment is only a part of the software, in fact it's a data aquisition system for an inertia dyno and I didn't have time yet to draw the schematic on some kind of software.
.
If you're not in a hurry, I will eventually translate it in english end draw the shematic, I could post it then...

Dany

Added after 5 minutes:

Ianp,
Thank you for your suggestion, but I'm a kind of newbie in analog circuits, do you have an idea of the components I should use or any link to a working design?
Regards,
Dany

Dany,
I do the same thing, an adquisition system for an inertia dyno, with a hall effect sensor detecting drum rpm, and I want to get pulses from the spark plug wire, what circuit are you using?

Thanks,
Enzo