Simple Outdoor Garden Solar Lights Circuit

Imagine tiny suns that light up your garden at night.

This outdoor garden solar lights circuit is like a mini power plant for your flowers.

It uses a solar panel to soak up the suns rays during the day and stores that energy in a rechargeable battery.

Then, when the sun goes down a clever circuit uses that stored energy to power LED lights, keeping your garden glowing all night long.

Circuit Working:

Parts List:

This project involves creating a hobby circuit for automatic garden lights using an LDR and a 9V 10W solar panel.

During the day a rechargeable 6V 4Ah battery charges from the solar panel through a polarity protection diode and a current limiting resistor.

If the ambient light is sufficient, a transistor T1 is turned off by an IC LM555.

This IC is set up as a medium current inverting line driver, controlled by a light detector 10mm LDR.

A multi turn trimpot adjusts the sensitivity of the detection.

When the ambient light decreases, transistor T1 turns on activating a string of white 3.3V straw hat type LEDs D1 to D8.

Resistors R1 to R8 control the current to the LEDs.

When the ambient light increases again the circuit returns to its idle state and switches off the lights.

To assemble the circuit, place it on a general purpose PCB and enclose it in a transparent plastic box.

Drill holes in the top of the enclosure for mounting the solar panel and light sensor and in the front for fitting the power switch and sensitivity controller.

Secure the battery inside the cabinet using double sided tape or pads.

Ensure that the LDR is not directly exposed to sunlight, mount it at the top of the enclosure facing southwards.

This circuit is basic, allowing hobbyists to modify it easily e.g. by adding a 6V relay with T1 to drive more LED strings.

Formulas:

We will combine a solar panel, a battery, LEDs, LDR and a few other parts to create an outdoor garden solar light circuit using the parts you mentioned.

The idea is to build a circuit that uses the LM555 timer IC to regulate the operation based on light levels measured by the LDR, so that LEDs light up when it becomes dark.

LED Current Limiting Resistor:

To get the resistor value required to restrict the current for each LED when connecting them in parallel, use the formula below:

R = V_battery​−V_LED​​ / I_LED​

where,

• Vbattery​ is 6V
• VLED is 3.3V forward voltage of the LED
• ILED is desired current around 20mA per LED

With this configuration, an automated garden lighting system will be available, which will turn on the LEDs when the light level drops below a predetermined point.

How to Build:

To build a Simple Outdoor Garden Solar Lights Circuit you need to follow the below mentioned connections steps:

Solar Panel and Battery Connection:

• Connect the positive terminal of the solar panel to the positive terminal of the battery.
• Connect the negative terminal of the solar panel to the cathode striped side of diode D9.
• Connect the anode of D9 to the negative terminal of the battery.

IC and Transistor Connections:

• Wire the LM555 timer IC as an inverting line driver.
• Refer to the LM555 datasheet for the pinout and configuration.
• Connect the output of the LM555 IC to the base of transistor T1.
• Connect the emitter of T1 to the negative terminal of the battery.
• Connect the collector of T1 to the LED string D1 to D8.

LDR and Sensitivity Adjustment:

• Mount the LDR on the top of the enclosure, facing southwards.
• Connect one end of the LDR to the positive terminal of the battery.
• Connect the other end of the LDR to the inverting input of the LM555 IC.
• Connect trimpot P1 between the positive terminal of the battery and the inverting input of the LM555 IC.
• Adjust P1 to set the detection sensitivity.

LED Connections:

• Connect the anodes of the white LEDs D1 to D8 to the collector of T1.
• Connect the cathodes of the LEDs to resistors R1-R8.
• Connect the other end of R1 to R8 to the negative terminal of the battery.

Enclosure and Final Assembly:

• Place the circuit on a general purpose PCB and secure it inside the transparent plastic box.
• Drill holes in the top for mounting the solar panel and LDR and in the front for fitting the power switch S1 and sensitivity controller P1.
• Use double sided tape or pads to fix the battery inside the enclosure.

Testing:

• Test the circuit by placing it in an area with varying light conditions.
• Ensure that the LEDs turn on when the ambient light decreases and turn off when it increases.

Note:

• Please note that the specific values of resistors, the type of transistor and the number of LEDs in the string will depend on the desired brightness and power consumption of the lights.
• Adjust these components as needed for your application.

Conclusion:

An outdoor garden solar lights circuit harnesses solar energy to power LED lights offering a sustainable and efficient lighting solution for outdoor spaces.

This circuit includes components like a solar panel, rechargeable battery, charge controller, inverter or driver circuit and LED lights all enclosed in a weatherproof housing.

It provides illumination during the night while reducing energy costs and environmental impact.

References:

Solar Garden Lights

Datasheet IC LM555