Ultrasonic sensor application

The conductor cable from the HE-US23 has colored leads, RED, BLACK, WHITE/YELLOW, BROWN and GREEN. These wires are connected to a monitoring device (for example a PC with an I/O card). Wires RED and GREEN can be connected to any DC power supply, or a general DC adapter available at your nearest supermarket. Sometimes microcomputer I/O cards provide a power output, which can be applied to the HE-US23. The GREEN wire, is connected to the COMMON or GROUND on your monitoring device. The BLACK wire is connected to a digital output pin on the monitoring device, and the BROWN wire is connected to a digital input pin (preferably an interrupt pin or a time capture pin).

GRAPH A. represents the signal applied to the HE-US’S BLACK wire. The output pin on the monitoring device is set HIGH (5 volts), at time (T0), for a few milliseconds; after which it is cleared to LOW. This action will cause the HE-US23 to transmit 40Khz ultrasonic waves, for the duration of the pulse applied to the BLACK wire.

Assuming there is an object at X distance from the HE-US33, the ECHO caused by the transmitted waves will eventually return, this ECHO is available on the WHITE / YELLOW and BROWN wire. GRAPH B. represents the signals available from the WHITE wire.

At some time T1 following the pulse applied at T0, the signal reflected of the object will be returning. Measuring the time difference between T1 and T0, will help determine the precise distance to the object, causing the reflection. The distance in terms of meters, is calculated X = 344 * (T1-T0). GRAPH C. represents the signal on the BROWN wire. The signals on the BROWN wire are basically the signals on the WHITE / YELLOW wire, conditioned for a microcomputer digital input pin. These are 5V square pulses oscillating at 40Khz. If connected to an interrupt pin, the computer can branch to an interrupt service routine, and freeze a timer when the first wave front of the echo returns.