Our houses already use electricity to carry signals besides just power.
This post shows you how to build a remote control that uses the electricity in your walls 220V to send signals.
It works for short distances inside your house or apartment because the signal is at a much higher frequency 5 kHz than the regular electricity 50 Hz.
This makes it easy to separate the signal from the regular electricity.
WARNING: Building circuits that connect to the mains electricity can be dangerous.
Only do this with adult supervision.
What is a Power Line Communication Remote Control Circuit:
A Power Line Communication PLC Remote Control Circuit is an electronic circuit that allows for communication and control signals to be transmitted over existing power lines.
This technology enables remote control of devices or systems through the electrical wiring infrastructure within a building or a power distribution network.
Transmitter Circuit Operation:
Parts list for transmitter circuit:
| Component | Description | Quantity |
|---|---|---|
| Resistors | 1/4 W MFR | |
| 4.7k | 1 | |
| 56k | 1 | |
| 220Ω | 1 | |
| 1M | 1 | |
| Capacitors | ||
| PPC | 2.2nF | 1 |
| PPC | 100nF | 1 |
| PPC | 0.47μF / 400V | 1 |
| Electrolytic | 220μF 25V | 1 |
| Semiconductors | ||
| Diodes | 1N4007 | 2 |
| Transistors | BC547 | 1 |
| BC557 | 1 | |
| IC | 555 | 1 |
The chosen frequency for the transmitter, in this case 5kHz ensures effective separation from the 50Hz power line frequency.
The IC 555 integrated circuit serves as the oscillator generating the desired frequency.
The power amplifier, comprising two transistors amplifies the signal for transmission.
The output is linked to the phase voltage through a capacitor, which allows the high frequency signal to pass while blocking the lower frequency mains.
The transmitter can be powered by a battery AC/DC adapter, or a simple supply utilizing capacitor reactance to reduce voltage.
Control is achieved by either switching the power supply or applying a logical 1 to the 4th pin of the IC 555 determining when the transmitter is active.
Formulas:
Transmitter circuit for the 555 IC astable circuit with the following component values:
R1 = 4.7 k (resistance 1)
R2 = 56 k (resistance 2)
C1 = 2.2 nF (capacitance)
We can calculate the following:
Time Constant 1 (Charge Time):
T₁ = R₁ * C₁
T₁ = 4700Ω * 2.2nF
T₁ ≈ 10.34 ns (nanoseconds)
Time Constant 2 (Discharge Time):
T₂ = R₂ * C₁
T₂ = 56000Ω * 2.2nF
T₂ = 123.2 ns (nanoseconds)
We can calculate the frequency (f) using the following formula:
f = 1 / (ln(2) * (T₁ + T₂))
where,
- ln(2) is the natural logarithm of 2 (approximately 0.693).
- f = 1 / (0.693 * (10.34 ns + 123.2 ns))
- f = 1 / (0.693 * 133.54 ns)
- f = 7.49 kHz (kilohertz)
Duty Cycle D:
D = (T₁ / (T₁ + T₂)) * 100%
D = (10.34 ns / (10.34 ns + 123.2 ns)) * 100%
D = 7.7% (Due to the dominance of R2, the charge time is significantly smaller than the discharge time, resulting in a low duty cycle)
Summary:
- Oscillation Frequency (f) = 7.49 kHz
- Duty Cycle (D) = 7.7%
Receiver Circuit Operation:
Parts list for receiver circuit:
| Component | Description | Quantity |
|---|---|---|
| Resistors | 1/4 W MFR | |
| 4.7k | 1 | |
| 1k | 1 | |
| 220k | 1 | |
| 470Ω | 1 | |
| 330k | 1 | |
| 820Ω | 2 | |
| Capacitors | ||
| PPC | 15nF 250V | 1 |
| PPC | 330nF 250V | 1 |
| PPC | 22nF | 2 |
| Electrolytic | ||
| 220μF 25V | 1 | |
| 470μF 16V | 1 | |
| Semiconductors | ||
| Diodes | 1N4007 | 3 |
| Transistor | BC557 | 1 |
| Triac | BT136 | 1 |
| Bulb | 220V | 1 |
The high pass filter at the receivers input separates the transmitted signal from the mains voltage ensuring only the desired signal enters the circuit.
The transistor with a base resistance of 220k regulates the current to the triac gate.
When open the triac is closed, when closed intermittently (during signal reception) the triac opens.
The triac operates in the II. and III. quadrants enabling it to control loads with a maximum current of 4A.
Signal reception triggers the triac to open allowing power to flow to the connected load.
The receiver is directly powered from the mains through a 330n capacitor.
The 330k discharging resistor and the 470 ohm limiting resistor manage the current during power on preventing spike.
Transmitter Construction:
For short distance transmission a frequency range of 1 to 25kHz is suitable.
In this design a transmitter frequency of 5kHz is chosen providing a 100x difference from the power line frequency for effective separation.
ftransmitter = 5 kHz
The oscillator is constructed using an integrated circuit 555 combined with a power amplifier featuring two transistors.
Diodes are employed to protect the transistors from voltage surges.
The output is connected to the phase voltage through a capacitor with a capacity ranging from 220nF to 470nF, rated for 250V AC, Class X2.
Ccapacitor = 220n to 470n
Vrated = 250V
The transmitter can be powered by a battery AC/DC adapter or a simple supply using capacitor reactance to reduce voltage.
The transmitter is controlled by either switching its power supply or applying logical 1 to the 4th pin of the 555.
Receiver Construction:
The power line receiver incorporates a high pass filter at the input to separate the signal from the mains voltage.
This ensures effective signal detection.
A transistor maintained in an open state by a base resistance of 220k regulates the current flow to the triac gate.
The triac is closed when the transistor is open.
Signal reception causes the transistor to close intermittently charging the capacitor through two resistors (820 ohm) and subsequently opening the triac.
Rbase = 220k
Rresistor = 820R
The triac operates in the II. and III. quadrants allowing connection to loads with a maximum current of 4A.
Imax = 4A
The receiver is powered directly from the mains through a 330nF capacitor.
It includes a 330k discharging resistor and a 470 ohm resistor to limit the current peak at power on.
Cpower = 330n
Rdischarging = 330k
Rlimiting = 470R
Signal Range Considerations:
The coil of the electricity meter naturally attenuates higher frequencies eliminating the need for additional filters within an apartment or house.
Classic fluorescent lamps may pose an issue due to power factor capacitors.
Disconnection or the addition of serial RF chokes are suggested solutions.
Safety Precautions:
- Both the transmitter and receiver are electrically connected to the network.
- Utilize suitable fuses in power inputs to ensure safety.
- The construction and use of the 220V power line communication remote control circuit is at the individuals own risk.
- The author does not assume responsibility for any injuries or harm incurred.
Conclusion:
Power Line Communication is commonly used for applications such as home automation smart grid systems, and industrial control, where the existing power lines provide a convenient medium for communication between devices.
Commercially available PLC modules and integrated circuits simplify the implementation of PLC remote control circuits.
References
Design of Power-Line Communication System (PLC) Using a PIC Micro-controller