Wireless charging is everywhere these days, from your phone to fancy medical devices.
This post shows you how to build a simple wireless LED light circuit using a common chip called the IC 555.
It will let you see how wireless charging works by lighting up an LED without any wires!
What is a Wireless LED Light Circuit:
A Wireless LED Light Circuit refers to an electronic circuit that enables the control or operation of LED lights without the need for physical connections like wires.
This wireless control can be achieved through various technologies such as radio frequency RF, infrared IR, Bluetooth or Wi-Fi.
The purpose of such circuits is to provide flexibility and convenience in controlling LED lights making them suitable for applications like remote control lighting systems.
Circuit Diagram
Parts List:
| Component | Description | Quantity |
|---|---|---|
| Resistors | 1k CFR 1/4 W | 1 |
| 10k CFR 1/4 W | 1 | |
| 10Ω CFR 1/4 W | 2 | |
| 10Ω 1W | 1 | |
| Capacitors | Ceramic 3.3nF | 1 |
| Ceramic 0.1µF | 1 | |
| Electrolytic | 1000µF 16V | 2 |
| Semiconductors | Diode 1N4007 | 2 |
| MOSFET IRF540 | 1 | |
| IC 555 | 1 | |
| LEDs | 5mm White High Bright, 20mA | 12 |
| Coil | As specified in the text | 2 |
Transmitter Circuit Working:
The 555 IC is configured as an astable multivibrator to produce a continuous 20KHz square pulse.
Resistor R1 and R2 along with capacitor C1 determine the timing of charging and discharging cycles.
As capacitor C1 charges through resistor R1 and discharges through resistor R2 it creates a continuous cycle of oscillation.
When the voltage across capacitor C1 reaches 2/3 of the power supply VCC the internal flip flop of the 555 IC changes its state.
This causes the discharge pin 7 to go low initiating the discharge of capacitor C1 through resistor R2 and the discharge pin.
As the voltage across the capacitor decreases to 1/3 of VCC, the flip flop changes its state again and the discharge pin goes high.
This cycle of charging and discharging repeats generating a continuous square pulse at the output pin pin 3 of the 555 IC.
The square pulse generated at the output pin is fed into the Gate terminal of the IRF540 N Channel MOSFET.
The MOSFET acts as a switch turning ON during positive pulses and turning OFF during negative pulses.
The switching of the MOSFET results in discrete ON and OFF states for coil L1 connected to the Drain terminal.
This generates a strong fluctuating electromagnetic field around Coil L1.
Receiver Circuit Working:
The Receiver Coil L2 is placed in the proximity of the transmitter Coil L1 to capture the fluctuating electromagnetic field.
The fluctuating electromagnetic field induces a current in the Receiver coil L2 according to faradays law of electromagnetic induction.
Diode D1 connected to one end of the Receiver Coil acts as a rectifier.
It converts the pulsating AC induced in the coil into a unidirectional DC signal.
The rectified signal is then passed through a voltage doubler circuit increasing the potential difference enough to drive 12 LEDs.
The potential difference generated is used to illuminate the connected LEDs in the circuit.
Formulas and Calculations:
Here we can calculate the following formulas for astable 555 IC:
Flashing Frequency:
We can use the formula:
Frequency = 1 / (1.1 * R1 * C1)
where,
- Frequency (f) is in hertz Hz
- R1 is the resistance of resistor R1 in ohms Ω 1k
- C1 is the capacitance of capacitor C1 in farads F (3.3nF = 3.3 x 10-9 F)
Calculation:
f = 1 / (1.1 * 1000Ω * 3.3 x 10-9 F)
f = 294.1 Hz (rounded to one decimal place)
As a result, the circuits flashing frequency is roughly 294.1 Hz.
This indicates that there will be around 294.1 flashes of the LEDs every second.
The duty cycle is the percentage of the whole cycle time (on and off time) that the 555 IC output is high (LEDs on).
The following formula can be applied:
Duty Cycle = R2 / (R1 + R2) * 100%
where,
- Duty Cycle is a percentage (%)
- R1 is the resistance of resistor R1 in ohms Ω 1k
- R2 is the resistance of resistor R2 in ohms Ω 10k
Calculation:
Duty Cycle = 10kΩ / (1kΩ + 10kΩ) * 100%
Duty Cycle = 90.9% (rounded to one decimal place)
This indicates that the LEDs will be illuminated for about 90.9% of the cycle and off for the remaining 9.1%.
Summary:
The circuit will provide a duty cycle of about 90.9% and a flashing frequency of about 294.1 Hz with the component values provided.
This indicates that the LEDs will flash for a longer period of time while they are on than when they are off.
Remember:
These computations are predicated on the 555 IC operating flawlessly and having exact component values.
In practice, there may be small differences because of component tolerances and other issues.
Construction:
- Place the IC 555 on the PCB.
- Connect the VCC and reset pins to the positive supply on the PCB.
- Connect resistor R1 between the discharge pin 7 and the positive supply.
- Connect resistor R2 between the discharge pin and the shorted threshold and trigger pins.
- Connect capacitor C1 between the threshold and ground pins.
- Connect the trigger and threshold pins together.
- Connect resistor R2 between the shorted trigger and threshold pins and the discharge pin.
- Connect the gate terminal of the IRF540 MOSFET to the output pin of the IC 555 pin 3.
- Connect the drain terminal to the Transmitter Coil L1.
- Connect the source terminal to the ground supply on the PCB.
- Connect the positive terminal of the power supply to the VCC pin.
- Connect the negative terminal to the ground.
Transmitter Coil L1 Winding Details:
- Use Insulated Copper Wire 18 SWG
- Ferrite Core optional
- Use 18 SWG insulated copper wire for winding.
- Wind 25 turns of the insulated copper wire.
- Wind the wire around a suitable form, such as a cylindrical object to maintain uniformity.
- Connect one end of the coil to the drain terminal of the IRF540 MOSFET in the transmitter circuit.
- Optionally, you can use a ferrite core to enhance the performance of the coil.
- Wind the copper wire around the ferrite core for better coupling.
Receiver Coil L2 Winding Details:
- Insulated Copper Wire 22 SWG
- Use 22 SWG insulated copper wire for winding.
- Wind 100 turns of the insulated copper wire.
- Construct the coil by winding the wire carefully to avoid overlapping turns.
- Connect one end of the coil to the anode of diode D1 in the receiver circuit.
- The other end of the coil is typically connected to the ground or reference point in the circuit.
Additional Note:
- Ferrite Core for Receiver Coil optional
- Similar to the transmitter, you may optionally use a ferrite core for the receiver coil to improve performance.
- Wind the copper wire around the ferrite core.
Safety:
- Remember to maintain the integrity of the winding and avoid any short circuits between turns.
- The choice of the core material and the number of turns can impact the efficiency of the coils in transferring power wirelessly.
- Adjustments may be necessary for this simple wireless LED light circuit based on experimentation and specific project requirements.
Conclusion:
With both the Transmitter and Receiver circuits constructed, you can observe the wireless power transmission causing the LEDs to glow.
Ensure safety precautions while working with power supplies and electronic components.