Infrared automatic door controller principle and circuit

Figure 1 is the infrared receiver and motor drive circuit. When no one is around, the infrared receiver normally receives the infrared beam from the other side. Use a 60mm long guide tube (Figure 3) that is just inserted into the infrared transmitter tube to fix it parallel to the wall at an appropriate height and align it with the receiver on the opposite side. In this way, the infrared rays emitted are one beam and are not easy to interfere with the other receiver. The specific installation method is shown in Figure 4. After being amplified and filtered by BG6, BG7, CR, etc., the output is low level. At this time, BG5 is turned off, and BG2 and BG3 are turned on to perform the door closing action. When a person walks to the door, the infrared light is blocked, and BG7 outputs a high level and drives BG1 and BG4 through one limit switch to perform the door opening action. The other drive BG5 through R1 to turn off BG2. When the door opens to the specified position, the door opening limit switch is disconnected, so that the motor does not continue to run. When a person leaves, BG7 no longer outputs a high level, and the door closing action is performed after a delay of three seconds by capacitor C1.

The transmitting circuit can be modified from a TV remote control product (Figure 2). Remove the original transmitting tube and connect it to the dedicated transmitter that has been prepared with a lead wire. Connect the two transmitters in parallel and pay attention to the polarity. Then find a suitable button to short-circuit it and let it transmit all the time. It is best to use the "screen display" button to try not to interfere with the TV that may be in the radiation area. Use RW to adjust the transmitting power so that it can just be received.

Selection of main components: The four power tubes used in the motor drive circuit are IRF9540/P type/100V/19A and IRF540/N type/100V/28A field effect tubes. Because it is driven by voltage, it consumes almost no driving power. Its internal resistance is small and the temperature rise is very small. They can be installed on a small aluminum plate and pay attention to insulation. The motor can be bought from an auto parts store. A 12V wiper motor, its force arm is removed, and a gear from a four-stroke motorcycle engine is installed. It is connected with several small chains, and then a steel plate is used to make a bracket to fix it on the door. The specific installation method is shown in Figure 5.

In order to prevent power outages from affecting the normal use of the door, I designed a transformer to step down the voltage and use a 12V battery. The main circuit is powered by 12V and isolated from the mains, which improves safety.