0
\$\begingroup\$

I'm trying to build a frequency measurement circuit using NE555P and Atmega328P. The circuit is the following : enter image description here

I use this library https://www.pjrc.com/teensy/td_libs_FreqCount.html

Always, The system works fine at the beginning (3 to 4 minutes) and then the frequency values start to drop until reaching 0.

Does anyone knows what causes this strange behaviour ? Thanks in advance.

\$\endgroup\$
5
\$\begingroup\$

It is very difficult to see, but as far as I can tell it looks like you have the wrong pinout for the 555 timer. The pins on the right-hand side should be numbered 5-8 from the bottom up, not from the top down:

enter image description here

If you have it connected the way the picture shows, I expect that's why it's giving you problems.

\$\endgroup\$
  • 2
    \$\begingroup\$ +1 for eagle eyes... I did not spot that. \$\endgroup\$ – Trevor_G Mar 30 '17 at 16:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.