Radio remote doorbell circuit schematic

Photocoupler

This example presents a radio-operated remote-controlled doorbell system named "Ding Dong," featuring the TWH630/631 remote control module. When a visitor arrives, pressing the doorbell button on the door frame triggers a crisp and melodic bird sound, signaling the arrival of guests. For homeowners returning home, pressing the remote control switch in their pocket will produce a simple "beep" sound. This setup is particularly ideal for families with young children attending elementary school. Kids can leave without carrying keys, simply wearing a compact remote control and pressing it upon reaching their doorstep. Parents will instantly know their child is home safely.

The child has returned home.

Working Principle:

The remote doorbell system comprises two primary components: a remote control transmitter and a receiver. The circuit diagrams are illustrated in Figure a and Figure b, respectively.

The transmitter's main component is the TWH630 miniature radio transmitter, which broadcasts high-frequency signals into the air via its built-in antenna when the transmit button SB1 is pressed. The transmitter's modulation oscillator employs a standard 555 timer integrated circuit connected to a self-excited multivibrator. The output square wave frequency f = 1.44 / (R1 + 2R2)C1, as per the data provided in Figures a and b. Calculated to be approximately 1 kHz, the square wave signal is transmitted to the input terminal IN of TWH630 via resistor R3, modulating the high-frequency signal.

The receiver consists of a TWH631 radio receiver, an LM567 audio decoder, and a KI-156 ASIC. The TWH631 captures the signal emitted by the transmitter module and amplifies it before decoding it with the LM567. The center frequency of the decoder is primarily determined by RRP + R4 and C4, where Opf = 1.1 / (RRP + R4)C4. Adjusting the potentiometer RP ensures the center frequency matches the modulation frequency of the transmitter, which is 1 kHz. At this point, the 8-pin output of the integrated block outputs a low level, which is applied to the low-trigger terminal TG2 of IC5, triggering it to emit a "Ding Dong" signal. This signal is then amplified by transistor VT to drive the speaker BL, producing sound. IC5 is a "Ding Dong-Bird" music integrated circuit, featuring two trigger terminals: one high-level trigger terminal TG1, activated by a high level, with the OUT terminal emitting a bird sound when triggered; the other low-level trigger terminal TG2, which triggers a "Ding Dong" sound when activated by a low level, remaining inactive for high levels. SB2 is a button mounted on the door frame. When touched by a guest, SB2 is pressed, triggering the high-level trigger terminal TG2, causing the speaker BL to emit a "bird" sound.

Component Selection:

IC1 can use NE555, SI555, or similar time-based integrated circuits; IC2 and IC3 should employ TWH630/631 type radio transmission and reception modules; IC4 is the LM567 audio decoder; IC5 is the KD-156 "Ding Dong-Bird" specialized music integrated circuit. The integrated block is packaged in black paste, and resistors R6-R8, capacitor C5, and transistor VT can be soldered onto the small printed circuit board of the chip. VD1 and VD2 are common 1N4148 silicon switching diodes. Their function is to use the forward diode voltage drop to ensure the KD-156 operates under normal voltage.

VT can use a 9013-type silicon NPN transistor, requiring a current amplification factor β > 100.

RP is best suited for WSW organic solid trimmer potentiometers. Other RC components have no specific requirements, except that their size should be smaller.

G1 is best suited for a 12V battery dedicated to electronic lighters. G2 is connected in series by four fifth-dry batteries, providing a voltage of 6V.