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### Topic: RPM calclater (Read 6565 times)previous topic - next topic

#### AWOL

#30
##### Jul 19, 2011, 10:34 am
One technique I sometimes use is to turn on a 50% duty cycle PWM pin, and hook that to the input I'm testing.
May be a bit fast for this application, but at least it will show transitions.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
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#### Techone

#31
##### Jul 19, 2011, 06:29 pm
@ AWOL
Quote
One technique I sometimes use is to turn on a 50% duty cycle PWM pin, and hook that to the input I'm testing.
May be a bit fast for this application, but at least it will show transitions.

That is  a good idea AWOL, use the Arduino to generate a pulse. Or a 555 astable circuit set the the frequency you want. Or a second Ardiuno.  That way, it will check the "counter program""

@ robtillart

I am interest in this topic because it can be use a way to measure RPM ( ex : on a fan - using LED, Laser LED , IFR LEd ) or frequency counter. I will look at the "Sampling Routine" how you do it.

PS : This Forum is an exellent place to share ideas.

#### gshubham96

#32
##### Jul 19, 2011, 06:51 pmLast Edit: Jul 19, 2011, 07:12 pm by gshubham96 Reason: 1
Quote
A. Check the sensor with voltage to check if it have a 0 V for LOW and a 5 V for HIGH.
If not well the system will not work.

The output voltage of the sensor is 2.5V.
Is that the problem?? :~ :~

#### robtillaart

#33
##### Jul 19, 2011, 07:58 pm
Quote
The output voltage of the sensor is 2.5V.
Is that the problem?? smiley-confuse smiley-confuse

yes, there should at least be 2 voltages one for LOW and one for HIGH. and if 2.5V is the HIGH it might be well too LOW.

amplify the signal with a transistor ...
Rob Tillaart

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#### retrolefty

#34
##### Jul 19, 2011, 08:01 pm
Quote
The output voltage of the sensor is 2.5V.
Is that the problem??

How are you measuring that, while the signal is actively changing and using a DVM meter? If so that's not a true representation of the signal, use of a scope would be the only method to determine the active low and high voltage levels if the signal is changing.

Lefty

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