OlyMEGA Forums

Frequency counter
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Author:  polymorph [ Wed Feb 08, 2017 1:16 pm ]
Post subject:  Frequency counter

Although there are sample projects using Arduinos and Microchip PIC processors, and kits available using them... for ease of build and utility, hard to beat a chip dedicated to the purpose.


Intersil ICM7226
• CMOS Design for Very Low Power
• Output Drivers Directly Drive Both Digits and
Segments of Large 8-Digit LED Displays
• Measures Frequencies from DC to 10MHz; Periods
from 0.5µs to 10s
• Stable High Frequency Oscillator uses either 1MHz or
10MHz Crystal
• Both Common Anode and Common Cathode Available
• Control Signals Available for External Systems
• Multiplexed BCD Outputs
• Frequency Counter
• Period Counter
• Unit Counter
• Frequency Ratio Counter
• Time Interval Counter

The ICM7216 is a little newer, although both are classed as obsolete, they are still available from eBay for under $10 each.

I will look into using a Teensy 3.x as a frequency counter/period timer. An issue is the ability to calibrate, as the clock on the Teensy is not adjustable.

Looks like the FreqCount and FreqMeasure libraries are good from 0.1Hz to 65MHz. Shouldn't use any code that uses interrupts while doing this, though.
FreqCount: best for 1 kHz to 8 MHz (up to 65 MHz with Teensy 3.0 & 3.1)
FreqMeasure: best for 0.1 Hz to 1 kHz

To measure period on a Teensy should just need the use of micros() and an interrupt.

To get higher than 10MHz requires a prescaler. The MC12080 is capable of up to 1.1GHz, dividing 10, 20, 40, or 80.

Only $5 each from Mouser:

Author:  polymorph [ Wed Jun 07, 2017 9:14 am ]
Post subject:  Re: Frequency counter

I'm going to start by trying to build a frequency counter using a Teensy 3.0 with an LCD screen.

Then slowly integrate more functions including period timer, duty cycle measure, Ton/Toff measurement, etc.

Then start integrating control of a DDS like the AD9850/51/33.

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