Joule thief are small, fun circuits which exploit a few characteristics of electronics and LEDs in order to “steal” virtually all of the energy stored in a battery. They can operate at incredibly small voltages and are fairly simple to make. With a few modifications to this basic circuit it’s possible to drive other things than an LED, though, like this joule thief that lights up a neon bulb.
The circuit from [suedbunker] aka [fuselage] is based on a pin from the Chaos Communication Camp which had a standard LED. To get a neon light to illuminate a few modifications to the standard joule thief are needed.
First, the windings have to be changed from 10:10 to 10:80 to increase the voltage across the bulb. Second, a transistor with slightly different characteristics was used than the original design. The capacitor was also replaced with a larger one.
While it might seem simple, the physics of how a joule thief works are anything but, and modifying the delicate circuit to work with something other than an LED is commendable. It also has a steampunk vibe which is a cool look even in projects that don’t involve steam at all.
Thermoelectric devices are curious things, capable of generating electricity via the Seebeck effect from a temperature differential across themselves. The Seebeck effect does not produce a huge potential difference, but when employed properly, it can have some useful applications. [MJKZZ] decided to apply the technology to build a reading light, powered by a hot cup of coffee.
The build is based around four Peltier modules, 40mm x 40mm in size, sandwiched between a pair of copper sheets. The modules are wired in series to create a greater output voltage, and an aluminium heatsink is fitted to one side to create a higher temperature differential. The set-up produces just 230 mV from human body temperature, but over 8 volts when warmed directly with a heat gun. Boiling water in a mug produces a more restrained 2.1V output.
On its own, this voltage is a little weak to do anything useful. Thus, the electricity from the Peltier modules is fed through a joule thief, which helps step up the voltage to a more useful range to run an LED. With a mug of coffee on the copper plate, the assembly isn’t quite able to light the LED enough to allow the user to read comfortably. However, it flickers into life just a touch, demonstrating the basic concepts in action.
While it’s not the most practical build, and it’s likely to cool your coffee faster than you’d like, it’s a fun project that serves to educate about the mechanics of the Seebeck effect and using Peltier devices to generate it. Another fun application is to use them in a cloud chamber. Video after the break.
Continue reading “Reading Light Not Quite Powered By Your Favorite Hot Beverage”
Are you waiting for something that may never happen? Maybe it’s the end of your ennui, or the release of Half Life 3. While you wait, why not build a Godot Machine? Then you can diversify your portfolio and wait for two things that could happen today, tomorrow, or at sunrise on the 12th of Never.
The Godot Machine is a functional art piece that uses a solar panel and a joule thief to charge a bank of capacitors up to 5V. Whenever that happens, the Arduino comes online and generates a 20-bit random number, which is displayed on an LED bar. If the generated number matches the super-secret number that was generated at first boot and then stashed away in EEPROM, the Machine emits a victory beep and lights a green LED. Then you can go back to complaining about whatever.
We like that [kajnjaps] made his own chaos-based random number generator instead of just calling
random(). It uses a guitar string to collect ambient electronic noise and an entropy generator to amplify it. Then the four least significant digits are used to seed the logistical map, so the initial value is always different.
You don’t have to create your own entropy for truly random numbers, though it’s probably more fun that way. Did you know that someone wrote an Arduino entropy library?
White LEDs were the technological breakthrough that changed the world of lighting, now they are everywhere. There’s no better sign of their cost-effective ubiquity than the dollar store solar garden light: a complete unit integrating a white LED with its solar cell and battery storage. Not content with boring white lights on the ground, [Emily] decided to switch up their colors with a mix of single-color LEDs and dynamic color-changing LEDs, then hung them up high as colorful solar ornaments.
The heart of these solar devices is a YX8018 chip (or one of its competitors.) While the sun is shining, solar power is directed to charge up the battery. Once the solar cell stops producing power, presumably because the sun has gone down, the chip starts acting as a boost converter (“Joule thief”) pushing a single cell battery voltage up high enough to drive its white LED. Changing that LED over to a single color LED is pretty straightforward, but a color changing LED adds a bit of challenge. The boost converter deliver power in pulses that are too fast for human eyes to pick up but the time between power pulses is long enough to cause a color-changing circuit to reset itself and never get beyond its boot-up color.
The hack to keep a color-changing LED’s cycle going is to add a capacitor to retain some charge between pulses, and a diode to prevent that charge from draining back into the rest of the circuit. A ping-pong ball serves as light diffuser, and the whole thing is hung up using a 3D-printed sheath which adds its own splash of color.
Solar garden lights are great basis for a cheap and easy introduction to electronics hacking. We’ve seen them turn into LED throwies, into a usable flashlight, or even to power an ATTiny microcontroller.
Continue reading “Give Your Solar Garden Lights A Color Changing LED Upgrade”
Solar garden lights are just another part of the great trash pile of our age, electronics so cheap as to be disposable. Most of you probably have a set lurking somewhere at home, their batteries maybe exhausted. Internally though they are surprisingly interesting devices. A solar cell, a little boost converter chip, and a little NiCd battery alongside the LED. These are components with potential, as [Randy Elwin] noted with a mind to his ATtiny85 projects.
The YX805A chip he references in his write-up is one of several similar chips that function in effect as joule thieves, extending the available charge in the battery to keep the LED active as long as possible when their solar panel is generating nothing, and turning it off in daylight when the panel can charge. Their problem is that they are designed as joule thieves rather than regulators, so using them as a microcontroller PSU without modification can result in overvoltage.
His solution is to use the device’s solar panel input as a feedback pin from his ATtiny, allowing the microcontroller to keep an eye on its supply voltage and enable or disable the converter as necessary while it keeps running from the reservoir capacitor. Meanwhile the solar panel now charges the NiCd cell through a single diode. It’s not perfect and maybe needs a clamp or something, he notes that there is a condition in which the supply can peak at 8 volts, a level which would kill an ATtiny. But still, we like simple hacks on dollar store parts, so it’s definitely worth further investigation.
This isn’t the first garden light hack we’ve shown you, there was this flashlight, and some LED hacks.
Solar light picture: Leon Brooks [Public domain].
A lot of things tend to get stretched during the holiday season, like shopping budgets and waistbands and patience. This year, [Chris] is stretching the limits of both the mini breadboard and the humble 1.5 V LR44 coin cell with his joule thief-driven LED mini Christmas tree.
With the push of a micro momentary, the joule thief circuit squeezes enough power from an LR44 to boot an MSP430 microcontroller, which needs 1.8 V – 3.6 V. After boot, the micro takes control of the joule thief circuit and milks it whenever the voltage falls below 3.2 V. This tree may be small in stature, but it’s feature-rich. A push of the same momentary button cycles through four different light shows, ending with a medley of all four. Be dazzled after the break.
The code for this tiny tree, which features an awesome ASCII breadboard layout and schematic, is up on GitHub. [Chris] has it listed among a few other manageable bare-metal ‘430 projects that would be great for beginners at pure C. If that sounds like you, why not give yourself the gift of learning a new language?
We’ve seen some spirited ways of lighting LEDs, but doing it with candle power takes the fruitcake.
Continue reading “Joule Thief Steals In Favor Of Christmas”
A common project among electronics tinkerers is the joule thief, a self-oscillating circuit that can “steal” the remaining energy in a battery after the voltage has dropped so low that most devices would stop working. Typically the circuit powers an LED until almost all of the energy is extracted from the battery, but [Lionel Sears] has created a specialized joule theif that uses the “extra” energy to power a clock.
The circuit uses four coils instead of the usual two to extract energy from the battery. The circuit charges a large capacitor which provides the higher current pulses needed to drive the clock’s mechanism. It can power the clock from a single AA battery, and will run until the voltage on the battery is only 0.5 volts.
Normally the clock would stop running well before the voltage drops this low, despite the fact that there’s still a little chemical energy left in the batteries. The circuit can drive the clock for an extended time with a new battery, or could use old “dead” batteries to run the clock for a brief time while the final little bit of energy is drawn from them. If you’re so inclined, you could even use hot and cold water with a joule thief to run your clock! Thanks to [Steven] for the tip.