Active antenna for the radio

Infrared receiver and motor drive circuit

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The new house was fitted with an aluminum alloy sliding door and finally had the opportunity to design an automatic door for itself. The human body detection part adopts the transmitting and receiving technology of the household appliance remote control, and is not affected by the ambient light.

Figure 1 shows the infrared receiving and motor driving circuit. When no one is in the infrared receiver, the infrared beam from the other side is normally received. The guide tube (Fig. 3), which is inserted into the infrared emission tube with a length of 60 mm, is fixed in parallel on the wall, and the height is appropriate, and is aligned with the opposite receiver, so that the infrared rays emitted are one bundle and do not easily interfere with the other receiver. The specific installation method is shown in Figure 4. After BG6, BG7, CR, etc., the amplifier outputs a low level. At this time, BG5 is turned off, and BG2 and BG3 are turned on to perform the door closing action. When the person walks to the door, the infrared light is blocked. The BG7 output high level drives the BG1 and BG4 to open the door through one limit switch, the other way drives the BG2 through R1 to turn off the BG2. When the door opens to the specified position, the threshold is opened. The position switch is opened so that the motor does not continue to run. When the person leaves, the BG7 no longer outputs a high level, and the door closing action is performed after a delay of three seconds by the capacitor C1.
The transmitting circuit can be modified by the TV remote control (Fig. 2). The original transmitting tube is unloaded and connected to the dedicated transmitter that has been completed. The two transmitters are connected in parallel and pay attention to the polarity. Then find a suitable button to short-circuit it, let it always emit, preferably the "on-screen" button, in order to try not to interfere with the TV set that may be in the radiation zone. The transmit power is adjusted with RW so that it can be received as well.

Main component selection: The four power transistors used in the motor drive circuit are IRF9540/P/100V/19A and IRF540/N/100V/28A FETs because they are voltage-driven and consume almost no drive power. It has a small internal resistance and a small temperature rise. They can be mounted on a small aluminum plate and pay attention to insulation. The motor can go to the auto parts store to buy a 12V wiper motor, remove its force arm, install the gear of a four-stroke motorcycle engine, connect it with several small chains, and then fix it on the door with a steel plate as a bracket. The specific installation method is shown in Figure 5.

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