This solar garden light circuit uses just one special switch a transistor and the power of the sun to light up an LED at night.
It works like magic when the sun goes down, the light automatically turns on and when the sun comes back up the light turns off.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | 1k, 47Ω, 470Ω (1/4 watt each) | 1 each |
| Semiconductors | Transistor BC547 | 1 |
| Diode 1N4001 | 1 | |
| LEDs | White straw hat 5mm, 20mA | 5 |
| Power Sources | Solar panel 6V | 1 |
| Battery 4.5V to 6V | 1 |
This project builds a night light that automatically turn on LEDs when it is dark and turn them off during the day.
The circuit uses the voltage from the solar panel to control the LEDs.
During the day, sunlight hitting the panel keeps the LEDs off.
At night, with no sunlight, the circuit turns on the LEDs.
Do not connect LEDs in parallel unless they are precisely matched for brightness.
Use a separate circuit for any LEDs that are dimmer.
Charging time depends on battery size and solar panel wattage.
Expect 6 to 8 hours for a 600mAh battery with a 0.5w panel and up to 2 days for a 1800mAh battery with a 1w panel.
The 47 ohm resistor might need adjustment based on the battery voltage and the number of LEDs.
This explanation assumes the battery is completely drained overnight.
Formulas:
Ohms Law formula is used to determine the resistor R2 value that regulates the current flowing through the LEDs in the above circuit:
R = V / I
where,
- In ohms Ω, R represents the resistance.
- The voltage across the resistor is denoted by V.
- I represents the current flowing via resistor A
To get the value of resistor R2, the following information must be known:
LED Forward Voltage Vf: The LED datasheet usually contains this information.
A white LED, for instance, may have a forward voltage of about 3.3V.
Number of LEDs in Series Ns: The Vf of a single LED must be multiplied by Ns if there are several LEDs in series.
Desired LED Current Id: The datasheet for the LED has this information as well.
A white LED may typically draw 20 milliampers (mA), or 0.02 amps A.
How to Build:
To build a Simple Solar Garden Light Circuit using One Transistor follow the below mentioned steps for components connections:
- Connect the positive supply to one end of 6V solar panel, and negative supply to other end.
- Connect the collector of transistor Q1 to resistor R2.
- Connect base of transistor Q1 to resistor R3.
- Connect emitter of transistor Q1 to ground.
- Connect positive supply to positive side of 4.5V to 6V battery and negative supply to negative side of battery.
- Connect 5 straw hat white LEDs one end to positive supply and other end to resistor R2 connected through transistor Q1 collector.
- Connect a D1 diode to negative supply from negative side of battery to to negative side of solar panel.
Safety Note:
- Avoid accidentally shorting circuit components.
- This can damage them or cause overheating.
- Double check connections before powering the circuit.
Conclusion:
A Solar Garden Light Circuit using One Transistor offers a simple and cost effective way to create an automatic night light powered by the sun.
Remember to prioritize safety while building and enjoy your sustainable garden light.
References:
Can you explain how the following garden solar light circuit works?
Good afternoon firstly thank you for the above Simple Solar Garden Light Circuit using One Transistor. As a first timer to electronics i have been looking for something like this. I have a solar garden light that my daughter bought me but it is not solar and has 3 candles that are each lit by x3 1.5v batteries. As you can guess this has become quite expensive buying batteries so i’d like to convert it to a solar light that i can run all 3 candles (one LED per candle) off of the above circuit. However i have all of the components but i’m confused how the circuit diagram would look on a homemade circuit board. Could you help me with this please. Accept if this is to much to ask?
Hi Kevan, thanks for your question.
Are you looking for the complete schematic that would integrate all the 3 candles with the above circuit?
If yes, then I can certainly help you…