Guest room power automatic controller

The hotel room "card" type power saving controller introduced in this article can be installed at the door of the guest room. The "card" is together with the key. When the guest enters the room, the power is automatically turned on by inserting the "card"; when leaving the room, the "card" is taken out, and the power is automatically cut off after a delay of 30 seconds. This prevents the waste of electricity due to the high mobility of guests who easily forget to turn off the power.

Since the core components of the power-saving controller adopt photoelectric coupler and bidirectional thyristor contactless control, the disadvantage of the old relay structure being easy to be damaged is overcome.

Working principle: The electrical principle is shown in the attached figure. Its circuit structure can be divided into three parts: working power supply, AC path and automatic control. The resistor R9, R10, capacitor C3, voltage regulator D3 and diode D2 form a RC step-down rectifier circuit. The output 9V DC voltage is filtered by electrolytic capacitor C2 as the working power supply. Here R10 prevents the AC power from instantly breaking down the voltage regulator D3. The AC path is composed of photocoupler IC1 and bidirectional thyristor BT139. The electrical appliance provides 220V AC power during the on time. When it is turned off, the AC power is automatically turned off. The 470V varistor is connected in parallel to limit the voltage of the bidirectional thyristor. The automatic control circuit is composed of operational amplifiers A1 and A2 and peripheral resistors R1, R2, R3, R4, R5, etc., and includes the input stage "infrared components" LED1 and BG1 to control the output stage AC path. The resistor R5 and capacitor C1 are delay circuits, and the time is about 30 seconds.

Its working process is as follows: Under normal circumstances, that is, when there is no guest in the room, LED1 transmits an infrared signal to the photoelectric receiving tube BG1, making BG1 conductive. At this time, the non-inverting input terminal ③ of the voltage comparator A1 is at a low level, and its inverting input terminal ② is at the midpoint voltage, so the output terminal ① is also at a low level, that is, Al=0 state: Since the inverting input terminal ⑥ of the subsequent voltage comparator A2 is also at the midpoint voltage, and the non-inverting input terminal (7) is at a low level, that is, A2=0 state, it has no effect on the subsequent output stage AC path. If a guest enters the room and inserts a "card", the infrared signal is blocked, causing the photoelectric transistor BG1 to be cut off, and the voltage of the non-inverting input terminal ③ of the voltage comparator A1 rises, that is, the input voltage is greater than the midpoint voltage of the inverting input terminal ②. The working state is just the opposite of the above: A1=1, A2=1, so the light-emitting diodes on the first and second pins of the photocoupler IC1 are turned on, and the bidirectional thyristor BT139 is triggered to turn on, the mains power is automatically connected, and the electrical appliances in the room can work normally (Editor: Power supply through the bidirectional thyristor has an impact on some electrical appliances with switching power supplies); if the guest leaves the room and takes out the "card", the circuit returns to the starting state, but because the "RC" delay circuit is connected to the output end of the voltage comparator A1, at this time, the charge on the capacitor C1 must be discharged through the resistor R5, and it takes about 30 seconds to be lower than the midpoint voltage, and the circuit starts to work, that is, A1=0, A2=0, and the electrical appliances are automatically turned off when the mains power is on.