using twelve light emitting diodes. The prototype has a CD4040 as counter and a CD4060 as the timebase generator. Gating the signal is by a resistor - diode gate. CMOS ics used here allow the instrument to be powered by any voltage in the range of 5 to 15 volts, but the maximum frequency is limited to about 4 MHz.
The 4040 is a twelve stage binary counter in a 16 pin package. The 4060 is a fourteen stage binary counter and oscillator, in the same 16 pin package.
The 74HC or 74HCT versions of these chips may be used for a higher frequency range, but the supply voltage range is then limited to a maximum of 5.5 volts or so.
In order to use this in order to display the frequency of a typical HAM transmitter, some sort of a prescaler and a preamplifier will be needed. Hopefully these shall be the subject of a subsequent instructable.
Step 1: Twelve LED Array
I started on this project in order to have a simple frequency counter which would work with the minimum of hassle, using the fewest number of components and NO programming. I settled on this "two chip frequency counter" design because its simplicity was appealing.
The first step was to wire the counter and make it work. I rounded up a number of red 3mm leds from my junk box and various boards and soldered them up in line on a sliver of circuit board - the result is shown here next to the counter chip. This particular ic was extracted from another half-finished project, with the fervent hope that at least this one will end up finished.
The 74HC4040 will be a better choice if you are planning on building this. It can count to a higher frequency.