LEAP#439 QX5252 Solar Night Light
Inside most solar-powered garden lights is an ingenious little circuit comprising a rechargeable battery, solar cell, inductor, LED and a little IC that does all the magic:
- when voltage is detected from the solar cell, the LED is off and the battery will charge
- as the solar cell voltage drops off (gets dark), the chip runs a switching converter (using the inductor) to boost the voltage from the 1.x V battery sufficient to drive the LED
- when the battery voltage falls too low, it tuens off the boost converter to prevent over-discharge
The chips that do the work are typically 4-pin TO-94 packages and come from various sources. Some of the most common are the QX5252 and YX805. I’m using a QX5252 here as it is the one I found a reasonable datasheet for.
There are DIP versions of these chips that have an additional light control pin that can either be used as a simple on-off, or to adjust the PVC voltage at which the LED cuts-off. I’m not using this as I have the TO-94 package version.
This project is a simple demonstration build of the standard solar-powered LED circuit. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
A quick demo of the switching based on light conditions:
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LEAP#437 QX5252 Joule Thief
I recently “discovered” solar LED driver ICs, such as the QX5252 and YX805. They are mainly designed to drive LED lights from a low-voltage rechargeable battery, with solar powered charging.
A core function is a boost converter circuit (similar to a joule thief) that allows LEDs with a forward voltage of over 2V to be driven from a 0.9V-1.5V battery.
As a test and demonstration, I’m ignoring the solar charging aspect here, and using the chip to drive an LED from a 1.55V coin cell. It just needs an external inductor to work.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
Here’s a quick demo:
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LEAP#436 Vivian the Vibrating BEAM Bot
Whatever happened to BEAM robotics? Perhaps it was just a 90’s fad, now rendered irrelevant by cheap microprocessors. But just as we still enjoy tinkering with 7400-series logic, old and irrelevant technology has a special attraction for some;-)
And it turns out that these days there are some new tricks - such as using the QX5252/YX805 solar LED driver to boost the output of the photovoltaic cell (it’s like a joule thief in a TO-94 package).
“Vivian” is the result of my first experiments: a solar-powered jumping vibrobot that employs a classic FLED solar engine circuit with a QX5252 boost converter.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.
Here’s quick video of my first bench-top test:
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LEAP#434 Boldport Krell
The Krell is a handheld DSP synthesiser, with Buttons and potentiometers dial up a range of sounds. The Boldport project is a typically beautiful remix of a soldering project by James Hutchby of MadLab.
At the core of the circuit is a Microchip dsPIC33EP128MC202-I/SP. It’s an interesting choice - a digital signal controller that is really designed for precision motor control, now put in service of creating music (or at least weird sounds).
This project also features Snaptron buttons preset on adhesive backing. Instead of soldering, they just stick down as a single array. I can imagine this being a very efficient approach for small batch assembly.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
My first sounds of Krell..
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