Wireless remote doorbell

During the school's electronic technology interest group activities and voluntary home appliance repair activities, we came across a large number of damaged remote control doorbells, and found that almost all of them were caused by overheating of the current limiting resistor in the doorbell receiving part. After analysis, we learned that the receiving parts of these remote control doorbells are all powered by 220V AC. When the doorbell plays music, there is a current of about tens to one hundred milliamperes, and the capacity of the step-down capacitor used is 1 to 2 microfarads. As a result, not only does it waste power most of the time, but the current limiting resistor in series heats up seriously, which greatly affects the service life of the remote control doorbell. For this reason, we thought about how to design a long-life remote control doorbell that consumes almost no power.

1. Working Principle

The core of this remote control doorbell that consumes almost no power is a new type of green energy storage component - supercapacitor, which is designed through DC/DC conversion technology.

By using micro-power wireless transmitting and receiving modules and supercapacitors to store electricity, the problems existing in existing remote control doorbells are completely solved. The problem of the continuous drop in voltage at both ends of the supercapacitor during the discharge process is solved by using DC/DC converters; and the problem of electromagnetic interference and the mutual influence of doorbells between neighbors is solved by using encoding and decoding technology.

Figure 1 is the transmitting circuit. In addition to the button AN, there are only three electronic components, namely the micro-power transmitting module F05P, the coding integrated circuit HX2262 and the resistor R. The transmitting circuit does not consume power at ordinary times. After pressing the doorbell normally open button AN, the data signal encoded by the coding integrated circuit HX2262 is sent to the micro-power transmitting module F050P and then transmitted into the air. During the signal transmission period, the working current is also very small. The total current measured under the action of a 6V battery is only 6mA. The battery voltage used can be selected between 3~12V.

Figure 2 is the receiving circuit. The core components are super capacitor C2, DC/DC converter BL8530, micro-power remote control receiving module J04V, decoding integrated circuit HX2272 and music integrated circuit TR95. The AC mains charges the super capacitor C2 after passing through the extremely small 0.033μF step-down capacitor C1, low-power current limiting resistor R2, bridge rectifier diodes D1~D4, voltage regulator diode DW, and light-emitting diode LED. The current is usually very small, only more than 2 milliamperes. The energy stored in the super capacitor is converted by the BL8530 integrated circuit, inductor L, Schottky diode D5 and capacitor C3, and a stable 3V DC power is output to supply the micro-power remote control receiving module J04V, decoding integrated circuit HX2272 and music integrated circuit. When the transmitting circuit sends out an electromagnetic wave signal, the receiving module J042 can receive the signal and send it to the input pin of the decoder through pin ②. Only when the decoding setting in the decoder is consistent with the encoding setting in the encoder, the decoder pin has a high level output. This high level is added to the trigger end of the music integrated block through resistor R4, capacitor C4, and music selection switch K2, and the speaker emits the corresponding music sound. When the doorbell emits music, the required current of several tens of milliamperes is provided by supercapacitor C2. Since BL8530 can convert a voltage as low as 0.8V into a stable 3V output, after calculation and actual use, a 2F supercapacitor can ensure that the doorbell continues to sound for more than 20 seconds, which is equivalent to pressing the doorbell ten times, which can meet the needs of general family use. After the supercapacitor continues to sound for more than 20 seconds, it only takes more than ten minutes to charge back to a voltage of about 3V. When not in use, the entire doorbell can be unplugged from the AC socket and the power switch K1 is disconnected at the same time.

2. Component Selection

The micro-power transmitting module in the transmitting circuit uses F05P produced by the New Century Electronics Research Institute in Anyang City, Henan Province. This module has two operating frequencies of 315MHz and 433MHz, an operating voltage of 3~12V, a current of 2~10mA, and only four pins, pin 1 connected to the positive pole of the power supply, pin 2 to ground, pin 3 to data input, and pin 4 to the antenna. The encoding integrated circuit uses the micro-power HX2262, which has 18 pins and the pin is the encoding output. The oscillation resistor R is 3.3M.

The supercapacitor C2 in the receiving circuit uses 2F, with a withstand voltage of 5.5V. You can also choose a larger capacity, so that the music emitted by the corresponding doorbell can last longer. The DC/DC converter uses BL8530, with an output voltage of 3V. This is a switching boost voltage regulator chip with an efficiency of 85%. The minimum input voltage is only 0.8V, the maximum output current is 200mA, and the static current is less than 5.5μA. The micro-power remote control receiving module uses the J04V from the same manufacturer, with an operating voltage of 2.6~3.5V and an operating current of 0.15~0.3 mA. It has 6 pins, ① for antenna, ② and ③ for data output, ④ for testing, ⑤ for grounding, and ⑥ for the positive pole of the power supply. The remote control distance can reach 100m.

The decoding integrated circuit uses the micro-power consumption HX2272, which has 18 pins and the oscillation resistor R3 is 680kΩ. The music integrated block is TR95. The transistor is 9011. The step-down capacitor is 33nF, i.e. 0.033μF, and the withstand voltage is above 400V. The current limiting resistor R2 is 100Ω, the discharge resistor R1 is 22MΩ, the four rectifier diodes are 1N4007, the voltage regulator diode is 5V, the light-emitting diode is a small ordinary one, the inductor is 47μH, D5 is 1N5819, the capacitor C3 is 220μ16V electrolytic, and the anti-interference capacitors C5 and C6 are 0.01μF ceramic chips.

3. Circuit characteristics

1. The doorbell receiving part consumes almost no electricity. It has been calculated that it consumes only 1 kWh of electricity in about 9 years.

2. The service life is very long, which completely solves the problems of heating of resistors and voltage regulator tubes.

3. The supercapacitor used can be charged and discharged hundreds of thousands of times, with a service life of more than 30 years. It does not pollute the environment like batteries.

4. The transmitting and receiving circuits are very simple and the performance is very reliable.

5. The problem of the continuous drop in voltage across the supercapacitor during the discharge process is solved by using a DC/DC converter.

6. Solve the problem of electromagnetic interference and mutual influence between doorbells of neighbors by using encoding and decoding technology

7. Small size and low cost.

8. It can be used in various wireless remote control situations where the normal working current is not large but a large current is required for a short time, such as wireless remote control operation controlled by relays in industrial and mining enterprises.