Development of an Automatic Room Population Monitor

Abstract

The paper presents the design, construction and testing of an Automatic Room Population Monitor. It is used to determine the number of people in a room or other enclosure. It has both logistic and security applications. The design is realized using digital circuitry and light emitting diode (LED) light sources. When the light beams are broken in the entry direction, the counter increments. When broken in the exit direction, the counter decrements. The number showing on the display unit at any point in time is the number of people currently remaining in the enclosure. The design uses latches to clock the Up/Down counters in the circuit and hence determine the direction of motion. It has an alarm that produces a high tone for forward crossing (entry) and a low tone for exit, as well as LED directional indicators. For some security purposes, the alarm can be switched off. A control oscillator is used to reset the circuit after a reasonable time to prevent the circuit from responding in the event of someone crossing halfway. It also has a ‘zero detector’ to prevent the circuit from responding when the count is already at zero and a reset button in case the counting has to be restarted.