Frequency counter is a very important test instrument for Radio Amateurs, especially those who wish to develop or test circuits. There are lots of frequency counters in the market but building one was never so easy & exciting with Microprocessors doing lots of work for us.
I made this project on a single PCB for the reasons that my idea of a counter was to make it a portable and independent of bench supply. (Because I already have a bench frequency counter) In this counter, we have possibility to supply external 12V or have a 9V internal battery.
Two RF inputs are available, switched by a push switch to select "Direct" or "Pre-Scale" Which gives you selection of either Low VHF (to 35MHZ) or VHF/UHF measurement ranges.
Counter software is auto-ranging and drives a 16×1/2 LCD. Counter is designed on a 6 × 19cm PTH Double Sided PCB. I could make this board much smaller but I preferred this size, keeping in mind first time kit builders.
This documents provides schematics & completed pictures of the Frequency Counter.
Picture of the Completed Frequency Counter Top Side View:
Counter Input Section View:
Frequency counter Top View with LCD module removed:
Picture of Frequency Counter - Back Side, where PIC16F84A is installed:
In above picture, PIC16F84A and Pre-scale IC, which is a SMT device, are not fitted.
Four holes on the right hand side, below red push button switch are for 9V battery holder, when internal supply is used.
Schematic of the 35MHZ PIC 16F84A LCD Frequency Counter:
Schematic of 3.5GHZ Pre Scale Section Up-Grade:
Some Design Notes:
Picture of Personalize message at start-up:
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