Ultrasonic range finder
From emboxit
The hardware described here is built up on a single sided PCB, size 49 mm x 50 mm. An Atmel AVR ATtiny26 microcontroller handles all the needed tasks:
I2C slave operation: communication to the I2C master
Stimulation of a resonant circuit embedding the ultrasonic sender Murata MA40B8S by 40 kHz PWM signal with defined duty cycle ratio
Adjusting the amplification (from 200 to 3500 in 16 steps) during echo measurement according to a fixed time schedule
(change of effective resistors in the OpAmp feedback circuit)
Time measurement until the ultrasonic echo is received by the Murata MA40B8R
