Mains Remote Tranciever Alarm

Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic to cellar, simply plugging transmitter and receiver in the wall mains sockets. Transmission range can be very good, provided both units are connected to the mains supply within the control of the same light-meter. More: The 135KHz sinewave generated by the transmitter is picked-up from mains wiring by C1 and selected by the tuned circuit L1-C3. Q1 greatly amplifies the incoming sinewave and converts it in a 12V-peak squarewave. D4 & D5 limit the input voltage at Q1 base.

The described system operates as a wireless alert mechanism utilizing the existing mains power lines to transmit signals between a transmitter and a receiver. The transmitter is equipped with a pushbutton that, when pressed, generates a signal that activates an alert in the receiver, which can be either a sound or a light indicator.

The transmitter generates a 135 kHz sinewave signal that is injected into the mains supply line. This signal is coupled to the receiver through the electrical wiring without the need for additional radio frequencies or dedicated wiring. The receiver is designed to be plugged directly into a wall socket, allowing it to operate in various locations within a building, from the attic to the cellar. The effective transmission range is contingent upon both the transmitter and receiver being connected to the same electrical circuit, ensuring that the signal can be adequately conveyed.

In the receiver circuit, the incoming mains signal is first picked up by a capacitor (C1), which acts as a coupling component to filter and allow the desired frequency to pass through. This signal is then selected by a tuned circuit composed of an inductor (L1) and another capacitor (C3), which is tuned to resonate at the frequency of the transmitted signal. The resonance amplifies the 135 kHz signal, making it more detectable.

The amplified signal is then fed into a transistor (Q1), which serves as an amplifier. This component significantly increases the amplitude of the incoming sinewave, converting it into a 12V peak square wave output. This square wave is suitable for driving alert mechanisms such as buzzers or LEDs within the receiver.

To protect the transistor from voltage spikes, diodes (D4 and D5) are used to limit the input voltage at the base of the transistor (Q1). This ensures that the transistor operates within safe limits, enhancing the reliability and longevity of the circuit.

Overall, this system provides a practical solution for alerting users without the need for complex wiring or dedicated radio frequency equipment, leveraging the existing electrical infrastructure for effective communication between devices.Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic to cellar, simply plugging transmitter and receiver in the wall mains sockets.

Transmission range can be very good, provided both units are connected to the mains supply within the control of the same light-meter. The 135KHz sinewave generated by the transmitter is picked-up from mains wiring by C1 and selected by the tuned circuit L1-C3. Q1 greatly amplifies the incoming sinewave and converts it in a 12V-peak squarewave. D4 & D5 limit the input voltage at Q1 b 🔗 External reference