Tired of the feeble light from your Solar-rechargeable Garden lights? You can more than triple the light output with this new circuit. Works even with red or orange lights - as long as it runs off a single AA rechargeable battery!
Step 1: Remove the Old Circuit Board.
Cut the wires as close to the board as possible. We'll need the wires from the solar cell and the battery holder, so cut them as close to the circuit board as possible. If there are wires from a light sensor (colored Green here) we can cut those too - it's not needed anymore.
The board can go and join the others we removed from other projects.
Step 2: The New Turbo Circuit.
The new circuit uses fewer parts than the original but can deliver over 80mA, almost 4-times the current to a White or Blue LED while using about 250mA, which is double the efficiency of the original design.
We will need to use 1/2W LED, which are readily available on eBay:
here, or here. They each have slightly different products, but I've used both and they're both reliable.
The real star of this circuit is the driver transistor, FJN965, from Fairchild Semi. Capable of handling up to 5-amps of current in a TO-92 case, it will start at .9v and run the light until the battery drops to under 0.3-volts. You can get them from http://fairchildsemi.com
Resistors, capacitors and inductors can be obtained from your local supply houses (eg Radio Shack, The Source), Sure Electronics, or at online surplus stores, like http://AllElectronics.com
The second image shows the layout using a Perfboard. S+ and S- indicate the wires from the Solar cell.
Step 3: Perfboard? or Try Just Winging It Freehand...
We will be using a 100mA white LED with a 140-degree spread. Start by slipping the leads through a scrap piece of perfboard to keep it upright.
If you want to follow the perfboard assembly, do that now, then solder the leads to the finished board.
The circuit is simple enough that the whole thing can be assembled freehand, which I will show you here.
Start by flipping the case over and bend the shorter (-) lead of the LED flat against the plastic. Then push it INTO the plastic by holding a hot soldering iron against the end of the lead until it melts it. Now it's SOLID!
Step 4: What IS This Sh*t???
Making our many legged creature.
Start by holding the 'C' lead of the 2N3906 to the 'B' lead of the FPN965 and soldering them together.
When you have attached the 2 capacitors and the diode to the transistors, this section is done.
Let me emphasize the need to COOL the parts after applying solder. The rule-of-thumb is to blow on the solder for TWICE as long as you apply heat. So if the joint took 2 seconds, cool it for 4 seconds. Heat is the second highest cause of failed circuits. (Number one is operator/designer stupidity.)
A few more images of the process of building our amorphous creature. Fine needle nose pliers are a must-have for little circuits like this. As is a GOOD soldering iron with a 1/16" or 1/32" tip.
Step 5: Attaching to the LED
I've trimmed and cleaned up all the little solder joints and I've bent into small hooks the 3 leads which require attachments.
Step 6: A Quick Test, And...
The green wires from the Light Sensor is left unconnected.
A 'feature' of this circuit is that once on, it will not be 'distracted' by flashes of light, from passing cars etc.
Here's another approach to make your garden light more effective - by adding Bling to the Oomph!
If you like this, see other LED ideas on my website: http://Quantsuff.com
Step 7: Another Option.
I have a light which sits on a gate surrounded by tall trees, with perhaps a max of 3 hours of sunlight in the afternoon. I added a small 2v, 30mA solar cell which is glued on facing West. It is simply added in series with the existing one. I also put a 2000mAH Sanyo battery in. Now even on overcast and rainy days, I get a good light showing the gate.