红外门电路2例(Infraredgate2)

红外门电路2例 (Infrared gate 2)

This is an infrared gate with two sensors planned to use in the wall in the way behind a door. It can be applied in a toilet to keep track of that someone is inside exceeding a certain amount of time. After that time elapsed, the circuit triggers the digital output wich can turn border=0>

Schematics

The device consists of several parts, the most critical width=479 border=0>

To start testing the infra LED panel, you wil need the infragate amplifier panel and the small transmiter driver. The TX driver will generate the digital signal for the LED driver width=531 border=0>

It is also important to protect the receiver diodes from direct light as natural light will weaken the sensitivity of the diodes, and lamps will transform the 50/60 Hz modulation present in the line power. Small noise is not problem, but the received signal from the TX generator should be stronger to be able to detect it. After the ST adjustments, connect LEDs to the 74123's TTL outputs through proper value resistors. The 74123 here is used as a demodulator. If there is a periodic signal change width=456 border=0>

If still everything is correctly working at this point, the remaining digital circuit is the easy part of the work. The outputs of the previous circuit (LEFT, RIGHT) directly connect to the remaining part. The RS memory built from two NAND gates remembers the way of the last movement direction, so if someone is in or not. If you experience problems, connect another LED to pin 10 of the RS and check if this part does what it should. If there was any activity in the past minutes, the first timer is running, but it can only trigger the second timer part, if someone is still inside. The diode from the second timer output prevents resetting itself before the timing period is over in case of another movement. For a 1 minute timing (first timer) R=470k C=100u can be used, the second part would use R=1.5M C=470u for about a 15 minute timing (t=1.1RC). The output of the second timer (pin 9) can drive a relay activating the ventillator.