How to Build a Frequency Counter

Written by leena kudalkar
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How to Build a Frequency Counter
A frequency counter helps design electronic equipment with accuracy. (counter image by Franc Podgor...¡ek from

An electronic instrument works on a steady clock in the background. The clock is a digital signal of ones and zeros at a uniform interval. A frequency counter is a small electronic instrument that detects the frequency of clock cycles of another electronic gadget. Without a frequency counter, the designer of the gadget has to guess and estimate the frequency and adjust it accordingly. The frequency counter counts each clock pulse of a device and calculates frequency as number of pulses in a unit of time. A timer is usually fed to the system to restart or synchronise with the clock pulse.

Skill level:

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Things you need

  • Frequency Counter Kit from Sparkfun Electronics

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  1. 1

    Pull out the FunCount printed circuit board (PCB) from your FunCount Frequency Counter kit. Study all the components provided in the kit and what they are called.

  2. 2

    Solder in the four resistors on the blank FunCount PCB. R1 and R4 are 10 ohms and have the colour strips "brown black red brown." R3 and R5 are 390 ohms and have the colour strips "orange white black brown."

  3. 3

    Solder in the following on the PDB: the 0.1 uF capacitor C2, 22 pF capacitors C3 and C4, the 20 Megahertz quartz crystal Q1 (clock) and the light emitting diode (LED). Arrange the positive long lead on the LED to the right and closer to the screw terminal.

  4. 4

    Solder in the vertical cylindrical pot R2, 16-pin female header, 100 uF capacitor C1, and the 3-pin screw terminal. Keep the 16-pin female header as vertical as possible.

  5. 5

    Place the ATmega328 microprocessor, the central and main piece of the puzzle, in the 20-pin Integrated Circuit (IC) socket keeping the notch to the left. Bend the legs (pins) of the microprocessor gently, to fit it in. Solder the IC socket on the PCB at the marked place. You may solder the IC socket either before or after inserting the ATTiny2313, as both ways are safe.

  6. 6

    Solder in the 16-pin male header to the liquid crystal display (LCD). Keep the male header as vertical as possible, exactly like the female header.

  7. 7

    Attach a regulated five-volt input power supply to the circuit at the labels marked "+5V" and "Ground," on the screw terminal. Find the JST cable in the kit for this purpose. Your circuit is complete with a 5V current, and the LED should light up, blinking about every second.

  8. 8

    Turn the power off and insert the LCD into the female header. Turn the power back on. You should see the LCD light up with a frequency reading that comes gradually on the screen. If you do not see any text on the LCD screen, adjust the backlight pot R2 or turn it clockwise.

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  • Sparkfun Electronics provides tutorials on soldering, board assembly, programming firmware on the boards and many other electronics skills.

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