“How many observe Christ's birthday! How few, His precepts!”
Benjamin Franklin
Bunnings currently sells Solar Lights at $1 a pop, but they throw an insipid light and have a paltry 150 Mah NiMh battery that gives little joy hardly commensurate with the importance of the season. So we felt a little "pimp my light" session coming on, which happily coincides with great success on the joule thief front. A typical joule thief oscillates like mad, producing voltage that is suitable for an LED, in that it flickers so fast that the human observing is convinced it's a solid lamp. Our $20 oscilloscope reports a frequency of around 140KHz:
Crazy oscillations
So recently we've been wondering if we couldn't wring the last out of our batteries in a more productive manner. Obscure Russian web page to the rescue, and our reworked circuit has been tested and found wonderful for producing a solid DC current that is suitable for flickering LEDs (which contain a small IC). Indeed the exciting news is that we are able to sustainably power our favourite Attiny13 microcontroller, which has interesting possibilities for the future (watch this space).
So all is now in order for a retrofit of the Bunnings light - firstly, cut out the existing circuit and change out the anaemic 150 Mah battery with a more respectable 2100 Mah version. Then replace inadequate generic solar garden light circuitry with our modified version based on the QX5252 chip.
Out with the old, in with the new
Before you can say "stable DC current please" we have the new circuitry in it's old housing and ready for lashings of hot glue.
Not dodgy looking at all!
Finally we can close it all up and gaze upon a Christmas landing strip that Old Nick will be no doubt chuffed to visit come late December. Here is the new trace via the oscilloscope...
Stable as, Bro!
And if you are wondering what is the point of all this, here is the result before suturing as well as the view that Santa will get from above.
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