There are a lot of videos on Youtube about repairing solar garden lights; extending the battery life of a solar garden light so they run longer at night, and a myriad of other hacks.
This Instructable is a little different than the ones you find on Youtub. This is on up cycling garden lights from bright white to chip RGB or strobe LEDs.
Step 1: First Circuit
Now this is not about solar garden lights you just change the bright white LED to a chip RGB LED and they work like this first circuit.
With this circuit you can just replace the bright white LED with a chip LED, RGB or Strobe and the circuit works.
Step 2: Tools & Supplies
Diodes 1N4148 or 1N5817
LEDs Chip RGB or Strobe
Capacitors 0.1 uf to 10 uf
Screwdriver to open solar lights
Needle Nose Pliers
Step 3: Easy to Build Circuit
If you want to build your own circuit, this is the simplest and easy circuit to build.
4 volt solar cell
Chip RGB LED
5.6 kΩ resistor
100 Ω resistor
S8550 or any general purpose PNP transistor
3 x 1.2 volt batteries
How this circuit works is simple; when the sun is up a positive charge is applied to the base of the transistor opening the PNP transistor. This turns off the RGB LED allowing all the current to pass through the 1N5817 diode to charge the batteries.
When the sun goes down; the solar cell allows the current to flow the other way applying a negative charge to the PNP transistors base. This closes the PNP transistor and allows current from the batteries to flow through the RGB LED. The 1N5817 diode prevents the batteries from applying a positive charge to the base of the PNP transistor.
Step 4: Up Cycling a Solar Light With a Joule Thief
The 5252F joule thief is a simple device; it converts the 1.2 volts from the rechargeable batteries, to a voltage capable of powering the LED. Using the properties of the inductor, the joule thief turns the current on and off increasing the voltage and decreasing the current. You can see the switching current on an oscilloscope.
Step 5: Changing the LED
If you just change the LED it may not light up. The reason for this is the chip LED uses 10 more milliamps current than the white LED.
Looking at the 5252F data sheet you can see that the 270 uH inductor supplies 14.5 milliamps and the chip LED needs over 20 milliamps. From the 5252F data sheet you find you need to change the inductor to a 150 uH inductor.
Now the chip LED lights up however it doesn’t cycle through red green blue. When you connect the oscilloscope to the LED you can see what wasn’t in the data sheets. The chip LED needs DC current. The chip in the LED starts to count to the color change every time the power comes on, so every signal from the joule thief is start count and it never gets to the next color.
To fix this you need to add a buffer to the LED.
Step 6: The Buffer Circuit
The buffer circuit is just s diode and a capacitor added to the circuit between the joule thief and the chip LED.
The diode keeps the capacitor charged when the joule thief signal goes to 0 volts, now when you connect the oscilloscope to the chip LED there is just a little ripple in the DC current and the chip LED cycles through the different colors.
Step 7: Assemble and Set Up
Now that you have the RGB or Strobe garden lights working assemble them and place them outside in a spot where they can get full sun.
This is an entry in the
Colors of the Rainbow Contest