[Miroslav Hancar] wasn’t satisfied with abusing just a single component for our Component Abuse Challenge. He decided to abuse a whole assembly, in particular, some LED candles.
In this project, LEDs are abused as temperature sensors. When the temperature gets hot enough for long enough, the microcontroller will turn on its LEDs. How? A diode’s forward voltage is temperature-related. By monitoring the forward voltage, the microcontroller can infer the temperature and respond appropriately.
This particular project is really two projects in one, centered around a common theme, heat activation. The first version has four LEDs and, in response to heat, four LEDs flicker to simulate a real candle. The second version is also heat-activated, but it has only one LED. You can snuff out this LED by pinching the top of it with your fingers. You can see a demo of each version in the videos below.
You will find the schematics, Gerber files, and software in the project’s downloadable files. The candles use some of the features of the PIC12F1501 microcontroller, particularly the onboard ADC.
If you’re interested in the PIC12F1501 and LED light displays, be sure to check out SIM Card Connectors and White PCBs Make Huge LED Snowflakes Happen. We wish [Miroslav] every success in the Component Abuse Challenge. The deadline is November 11, so you still have a few days to get your submissions in!
There was a window of time post-transistor and pre-LED, when a certain magazine published a fun little circuit, a lot simpler than that one: Basically just a CdS photocell, transistor, and flashlight bulb. Made in the shape of a candle, but with the CdS cell discreetly positioned to ‘see’ the light bulb, but from below and off to the side a bit… The party trick was to “light” the “candle” with a lit match, lighting up the CdS cell, which turned on the transistor, lighting the bulb, and illuminated the CdS cell, keeping the light on. And to “blow it out” the trickster put his hand behind the “candle” while blowing, interrupting the light path to the CdS cell and turning off the light. My dad thought this was a funny trick. Yeah, times were simpler in 1970.
This is so funny to me. Low power candles.
The abuse in itself is melting the poor led with a butane flame.
This hack puts a new meaning to planned obsolescence. Joking aside, I think it’s quite a neat hack. But heating up something which may resist the heat is nicer for long levity. There are less hacky ways to achieve the same illusion, though. Like using a flame detector or ldr.
When you do have a fake flame which can be turned on with a lighter, it opens up a lot of effects and even magic tricks. With multiple networked lights, you can make it reveal the chosen card, etc.
Decades ago I recall seeing a circuit using the same diode trick. In that case blowing on the diode turned the candle off.
I seldom a/never/ comment but I quite like this…