Hi there
I am building a prototype project, similar to a frequency counter with a mega 2560 and want to display a frequency of as high as 75 Mhz
does anybody have a circuit for a pre-scaler that will bring down the frequency to something the arduino can actually decode at a good accuracy ?
Diagrams and advice would be appreciated
Thank you
There are lots of ways to make a Frequency to something converter.
That something can be a voltage, which the arduino can read and convert into a number from 0 to 1023. A low-pass filter will smooth the 75MHz out to a DC kind of level that is easily measured.
That something can be a time. If you take the 75 MHz and divide it down thru a counter, you can slow it down enough so that the high time and low time of a square wave can be measured. A divide by 10 counter will get you down to 7.5MHz.
Or you count the number of pulses in a time period and determine the frequency from there.
A low-pass filter will smooth the 75MHz out to a DC kind of level that is easily measured.
Before you do that you need to trigger a monostable with the signal to give a fixed width pulse. Just smoothing a frequency is not going to give you a different voltage output for diffrent frequencies.
Thank you for the replies
After going through some of my schematics i found this prescaler that was used on a bs-2sx basic stamp few years back ,it has a buffer then two divide by 10 chips bringing down the frequency to 750 Khz . Would i be able to get a resolution of 9 digits (eg 74.675.999.1)?
I have also seen a newer programmable prescaler chip using MC 12080- which i am trying to not use as there a 3 bcd inputs to the prescaler which determine the divide by range .As i would prefer it to be a fixed range and then do all the calculations via software.
Attached is a diagram of the circuit would it be suitable for the arduino mega ?
Would i be able to get a resolution of 9 digits
No.
You only have a 16MHz processor so that defines you fundamental accuracy. Any measurement is going to be subject to a + / - 1 clock cycle error. Work out what that gives you on a scaled down 75MHz signal but it is no decimal places at all.
