maybe i was not fast enough to go over 1hz ? (more than 60 press / second ?)
I will try again...

 

hi,
Ok,
Do you have a 555 that could configure as a 10Hz Astable on a bread board.?
E

 

Yes
I tried with 555 (actually this is how I started my post ) because my intention was to control that 555 using a digital potentiometer.

 

hi,
I realise that you are intending to use a 555 and pot, but I am trying to help you explain why all your Arduino frequencies are giving a doubled count value on the tacho.
I am trying to give you an idea for a simple reference frequency so that you can test the tacho for 'level or edge counting'

Eric
This is a 10Hz Astable.

 

Will do your schematic asap and post results

 

Ok, I don t have that 4u7 capacitor, I have 22u and 47u capacitors
Second thing, where should be output on your schematic?

Btw - I did schematic attached (rpm2.pdf) and is working but is not like I would. In the schematic attached I connected a 10k potentiometer between potm1 and potm2 and out to the device. I am not sure if this is answer your question

 

Update - I changed multiplier values in pwm library and I am close of what I want. So for the moment I will try make this work since is much easier to use only arduino timer
Will post some results after I have a conclusions

 

hi D,
On your circuit what is the purpose of R6,R7 & C10 .?
If you connected components directly to pin #3 you will change the frequency.

If you want a 50/50 square wave on the output, the best way is to add a buffer transistor, on pin #7.
Check this image.
E

 

If there is a stable frequency available in the arduino OS, then you can use a count-down counter to generate precise time intervals for high and low time periods of your square wave signal. But in addition, it is not that complex to use a binary counter IC to generate frequencies dividing down from a stable known crystal oscillator frequency. Probably faster to design than some program to run on that little arduino board, and far easier to understand exactly what is happening.

 

If you need an exact 50% duty cycle then use a flipflop and drive the trigger input at twice the frequency you want.