# DIY Solar Birdhouse Light

This solar birdhouse light is an economical circuit of a mini solar lighting system circuit is presented here. At the heart of the circuit is a mini 6V/2W solar panel. Here, this solar panel is used to charge a 4V/800mAh rechargeable battery through a charge current limiter circuit built around an adjustable 3-pin regulator LM317T (IC1).

Resistor R1 sets the output current. The lighting circuit comprising 20 white LEDs are directly powered the battery. Swich S1 is a simple on/off switch. Assemble the circuit on a small PCB and enclose in a suitable cabinet. Fix the solar panel on the top of the cabinet and power switch and LEDs on the front side.

Specification of a typical 6V/2W solar panel:

• Maximum Power (Pm) :2W
• Working Voltage (Vmp):9V
• Working Current (Imp) :220mA
• Open Circuit Voltage (Voc) :10.5V
• Power Tolerance:-3% to +5%

Assuming a 6 hour sunlit day, a 2 watt panel (near 150mA current set by the regulator IC1+R1) will pump about 900mAh into the battery. Solar charging current can be reduced by increasing the value of R1 ,say from 8.2 Ohm to 10 Ohm.

## Related Tutorials

• Colin Mitchell

The 6v solar panel needs to develop 5.5v to overcome the back-voltage developed by the battery when charging. The LM317T needs 1.5v across it and if the charging current is 100mA, the 8R2 develops 820mV across it. This is a total of 7.8v. The 6v panel will not develop 7.8v.

• Colin Mitchell

This circuit DOES NOT WORK.
There is no current limiting resistor for the LEDs and the battery can NEVER charge. It has a 3.6v ZENER across it !!!! That’s what a LED is.

• Darktempt

excuse me sir…. what is the value of R2? is it 8ohms or 8k ohms?

thx..

• P. Marian

If you are talking about R1, then is 8.2Ω with 1 Watt of power dissipation.

• sebastian

Without the Diode there will be reverse flow from the battery to the panel destroying the panel .

Its essential to add a diode

• N.SARVESH

May i know what will be the cost estimation for this project:)

• N.SARVESH

This is really a good site for the best projects:)

• Udhaya Raj

sir,
may i know how much will be the output voltage of LM317

• Ian

The common or adjust lead of the IC1 regulator LM317 should be connected to the NEGATIVE lead of the battery NOT the POSITIVE end, and then the circuit will work.

• T.K.Hareendran

Theoritically u r right.Just load 20 LEDs as shown in the ckt and recheck ur circuit.My prototype is still working well without any LED burnout!I am wtng for your reply based on “PRACTICAL” experiment.

• vimal

Hello,
The charging circuit part is OK 150mA is quite sufficient to charge the battery in about 5 hours or so also no worries of overcharging since the 317 is going to trickle the battery once its fully charged.
Problem is with the led circuit, since its not having any current limiting resistor!
white led drops around 3.2 typically and are rated for 25mA MAX and without the current limiting resistor for the (4-3.2) extra 0.8V the battery is going to pump more current and your leds are gonna die sooner.

• Sebastian Kushero

To Charge a battery the current MUST never exceed 10% of the rated Battery capacity . ideally it should be 80mA . If you want to prolong the life of your battery to give you the promised cycles of charging.

This is not an efficient circuit .and shurely it does not need the 317 which drops 1.25 volt . It need something that automatic in switching on and off .

Have sent a solar Garden Light schematic and PCB drawing for the same all you need is 2 Resistors, 1 Diode, 1 transistor and 20 LED lights and you can use a mobile battery 3.7V/1500mAh Solar panel Rated 5.5V/360mAh. (2W).

We also sel kits that use 2V/250mA Solar panels to charge 3.7V/1500mAh battery

• chandrugdcs

hallo sir iam prepare a solar panel sir college project sir please help me sir contact thankyou sir….

Looking for the latest from TI?