# 5hz to 500 Khz Frequency-Meter

Posted on Feb 5, 2014

Based on the famous AT89C52 microcontroller, this 500 Khz frequency-Meter will be enough to trace and debug most of your circuits, to adjust 555 timers frequency and perform all kind of frequency measurements in Digital circuits. And once you have this tool between your hand, you will get used to it to the point of no-return! and you will say rem

ember the days we adjusted the frequency by trial and error till we get it. ! To understand the block diagram below, you should recall the simplest definition of frequency: the number of occurrences within a given time period . What we are trying to do is to count the number of electric pulses during a time of one second. To do this we need a counter, to count the pulses, and a timer so that every 1000 milliseconds, the processor stop counting, calculate the frequency and display it, then start counting again from zero. Below (figure 1) this is the principle of operation of a frequency meter, however, to build a reliable frequency meter, we will need to do some more mathematical operations. For example: Some operations will accurately predict the frequency before waiting for a whole second to elapse, which will also increase the refresh rate. Another minor upgrade is to to display the average of the last 5 reading rather than displaying the frequency instantaneously (which can cause lot of display flickering if the frequency being measured is not very stable). Lets start by this easy part, to make the project look far-or-less like a profession lab equipment, well I simply built it in an old Avo-Meter, one of those you find in stores for less than \$5! (god bless china!), and then painted it all in black. (it was originally yellow!) and by the way, after I hacked that poor Avo-Meter, I also used the same leads for our...

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