Using FrequencyMeasure with 555l pulse generator

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Bignige

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Hi There!,

I'm very interested in using the FrequencyMeasure library to measure low frequency light waves. Up to now I just have an Adruino Uno but if the project develops I can see I would be better to get a Teensy.

To test the frequency measuring part of the project I am using a 555 timer ic pulse generator set at 100Hz approx. see circuit

https://drive.google.com/file/d/0B7pY4dDKKRISWUxtZmxieUlmMG8/edit?usp=sharing

I have connected the output to digital pin 8 on the uno and grounded the circuit to digital gnd on the board. The problem is that the output is not working. When I connect the signal to pin8 I get a random frequency in the results (either serial monitor or LCD) when I take the signal off the pin the value changes to another random frequency and if I touch the pins again another value is output etc.

I am just a beginner really with electronics and have little experiance with these microcontroller platforms so I would be greatful of some help and advice.

My questions are firstly:-

Can I use that circuit 'as is' to provide the signal. or is it inadequate in some way?

Should I be using the digital ground as a common ground for the external circuit?

What is likely to be the issue causing the failure to measure the frequency correctly?

my gut feeling (not very scientific) is a problem with the signal i.e. strength, waveform, voltage etc.

Cheers

Nigel
 
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No, I've put a voltage divider in to bring the output to less than 5v. Measured it to around 3v . Is there a way to test the pin to make sure it hasn't been blown?
 
After further investigation with the help of an oscilloscope I determined that the output if the signal was the cause. For some reason the circuit us not providing a pulsed signal. By using a basic astable 555 timer circuit I got the desired square wave signal. Hooked it to the arduino with frequencymeasure running and it works fine. I just need to find out why the original circuit didn't produce pulses.
 
The circuit as drawn is fine. I just had a wiring mistake. So circuit and frequency measure work together on the arduino uno. Measured frequencies from 12Hz to 1200Hz in tests.

Now to plan my project!
 
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