This uses Ultrasonics to monitor a doorway or an area up to 2 metres wide. When an object, human or inanimate, passes the sensors, the counter increases.
Altering VR1 will ensure only one count per detection occurs.
Pressing the PTM switch resets the counter and display to zero.
More dual counters can be connected directly together to increase the count.
Uses 40KHz transducers for the U/S TX and RX
Circuit Voltage: 6 to 9 volts
This can be any push to make switch.
Adjust VR1 with a screwdriver to "tune" the transmitter frequency. Move a hand in front of the sensors while tuning, look for the LED on the detector flashing.
Note Astable is shown upside down.
Set the "Range" to 2, (0.05-2.5s) with VR1 about midway.
IMPORTANT: The transmitter and sensor should be placed in parallel pointing to the area they are monitoring.