Summary of Shrieker using PIC16F676 Microcontroller
Summary: A simple PIC16F676-based shrieker generates square-wave tones from 10,000 Hz to about 22,600 Hz selectable by six binary switches. The power button applies Vcc to the PIC to start it; the chosen switch combination (bits 32..1) sets an input value 0–63. Frequency = 10,000 Hz + input*200 Hz. Output drives a speaker through a capacitor; speaker is rated to 7 kHz but worked. Measured personal hearing limits: left ear 14,600 Hz, right ear 13,200 Hz.
Parts used in the Shrieker using PIC16F676:
- PIC16F676 microcontroller
- Momentary power button (provides Vcc to PIC)
- Six SPST switches (binary inputs)
- Speaker
- Series coupling capacitor to speaker
- Power supply/battery
- Wiring/PCB or breadboard
Recently a cell phone ring tone was in the news – it’s 17,000 Hertz and meant to be heard by teenagers, but
inaudible to adults. Really got some people upset for some reason. It got me wondering – what frequencies can I
hear? I made the shrieker. It can generate tones from 10,000 Hz to 22,000 Hz.
It’s a simple project. The program doesn’t do much.
The button actual provides power to the PIC, so
pressing it starts the boot up. Six pins read the inputs of
six switches. This determines the frequency. After that,
the PIC just generates a square wave of that frequency
on one of its pins that goes right to the speaker with a
capacitor to round the edges some.
The speaker was only rated to 7000 Hz, but seems to
work fine.
With all switches in the off position, the frequency is
10,000 Hz. The switches function as binary inputs, most
significant digit on the right: 32, 16, 8, 4, 2, 1, so the
input can vary from 0 to 63.
frequency = 10,000 Hz + input*200 Hz
So the frequency range is 10kHz – 22.6kHz
The results?
My left ear can hear 14,600 Hz, my right 13,200 Hz.
For more detail: Shrieker using PIC16F676 Microcontroller
- What frequency range does the shrieker generate?
The shrieker generates tones from 10,000 Hz up to about 22,600 Hz based on switch input. - How is the frequency selected?
Six binary switches form a value 0 to 63; frequency = 10,000 Hz + input*200 Hz. - How does the button function in the circuit?
The button supplies power to the PIC; pressing it starts the microcontroller boot up. - What output waveform does the PIC produce?
The PIC generates a square wave at the selected frequency on its output pin. - Is the speaker adequate for high frequencies?
The speaker is rated to 7,000 Hz but was reported to work for the higher tones in this project. - Which microcontroller is used?
The project uses a PIC16F676 microcontroller. - How are the switch bits ordered?
The switches represent bits with the most significant bit on the right: 32, 16, 8, 4, 2, 1. - What frequencies could the author personally hear?
The author heard 14,600 Hz in the left ear and 13,200 Hz in the right ear.
