Introduction: Solar and Battery Powered Timed Shed LED Light
In this Instructable I will show you how I made a LED light in my shed. Since I don't have a connection to mains, I made it battery powered.
The battery is charged via solar panel.
The LED light is switched on via a pulse switch and switches off after a preset time. Since it is battery powered, I tried to make the quiescent current low.
The power is stored in a 18650 LiPo battery, the voltage of the battery is increased via a step-up boost converter to power the 12V LED strip. The power and timing is controlled via a TPL5111 and a IRLB8721PbF Mosfet.
Step 1: Step 1: the Circuit
There are many ways to make a timed light. I used the TPL5111 chip, because I had it in stock and I like its features and low power.
See the attached circuit which I will explain here.
Solar charging circuit
I used a solar panel with a female USB connector. Therefor I added a male USB connector to my circuit, to connected and detach the solar panel. The solar panel is connected to the input of the TP4056 charger via a 1N5819 diode. I used this schottky diode, because it has a low forward voltage. I added a jumper in the solar circuit so I could easily measure the charge voltage at this position. I also added a connection to charge the battery via a normal LiPo charger, since in advance I did not know whether the solar panel does deliver enough energy.
The 18650 battery is connected to the TP4056 charger module. It is important to use a TP4056 charger board with battery protection (charge, power and drain), since the 18650 cell is not protected itself. The power to the rest of the circuit is switched via a power switch.
See the TPL5111 datasheet for its specification and its pin description. Most important features are described here.
The EN/1SHOT is connected to ground, so the TPL5111 only enables the DRV pin once when activated.
The DONE pin is pulled low, it is important to not let this pin floating. I added an optional push button to manually switch the LEDs off before the timer ended.
The MDRIVE pin is connected to ground via resistor. The value of the resistor determines the on-time off the DRV-pin. In my case I used 18 k Ohm which results in an on-time of abouw 40 seconds. The MDRIVE pin is also connected to the LED switch. This is the switch to switch on the LEDs.
I used a normal cheap mains voltage switch. I glued a spring from a ballpoint at one side to make it a pulse switch. This switches the LEDs on for the preset time to get my bike out of the shed. However, I also added a slide switch to keep the LEDs on as long as the switch is on.
Step 2: Step 2: Build the Circuit
The building consists of three parts
- The PCB
- The charger circuit
- The switch modification
- Prepare the LED strip
See the attached pictures and captions for explanation.
For the LED strip: My step up boost converter can deliver max 2A, but voltage was reduced at 1.8 A. I cut 3 pieces of LED strip and interconnected them.
Step 3: Step 3: Assembly
Assemble all parts according to the circuit.
I had a nice enclosure in which I could fit the parts. I used a waterproof connector to feed in the wires.
The solar panel is mounted on the shed roof at a slight angle towards the South.
Step 4: Step 4: Test It!
Finally test the setup.
In bright daylight I measured 0.2 A of power from the solar panel, which is ok with me. When the solar panel is in the shade, this reduced to 25 mA.
In my setup the light works great and switches of after 40 seconds, according to the datasheet of the TPL5111.