Problem with pic-frequency-counter-lcd-tmr1 60Hz when zero signal is input
by martin
(Portão, Brasil)
Hello,
I have assembled the circuit for the pic-frequency-counter-lcd-tmr1 and loaded the hex file into the microcontroller. The frequency-counter works fine, except by the fact that its zero countig point ocurs at 60Hz. In other words, without any frequency sign stimulation, it is all the time showing 60Hz. What I'm doing wrong?
Comments for
Problem with pic-frequency-counter-lcd-tmr1 60Hz when zero signal is input
How to determine 60Hz noise input or PSU? by: John Main
If you are in America then the mains frequency is 60Hz!
That is what is causing the reading - your circuit is receiving 60Hz mains signal noise.
In the UK it would be 50Hz.
Is it caused by the circuit or the power supply.
Method 1 - use a 1k resistor. =============================
Put a 1k resistor from the counter input to ground.
If you have 60Hz reading then the 60Hz noise is getting in from your power supply. So get a better power suppy or apply filtering to the power supply fed to the frequency counter circuit.
If you get zero then the noise is being caused by pickup from the circuit associated with the input. So improve the circuit around the frequency counter input - remove all ground loops and long wires etc.
Note: If the input circuit is complex then move the 1k to ground point along the circuit blocks until the problem area is found.
Alternate method - to prove PSU is at fault ===========================================
Buy a PP3 (square 9V battery) rechargeable is best feed this 9V voltage into a 7805 with appropriate caps and then into your frequency counter 5V supply input.
When you see that the reading is zero you will know that something is wrong with the power supply i.e. it is feeding 60Hz noise into the frequency counter.
So get a better power suppy or apply filtering to the power supply fed to the frequency counter circuit.
