555 Timers Bring Christmas Charm To Miniature Village

January 2, 2025 by Tom Nardi 10 Comments

The miniature Christmas village is a tradition in many families — a tiny idyllic world filled happy people, shops, and of course, snow. It’s common to see various miniature buildings for sale around the holidays just for this purpose, and since LEDs are small and cheap, they’ll almost always have some switch on the bottom to light up the windows.

This year, [Braden Sunwold] and his wife started their own village with an eye towards making it a family tradition. But to his surprise, the scale lamp posts they bought to dot along their snowy main street were hollow and didn’t actually light up. Seeing it was up to him to save Christmas, [Braden] got to work adding LEDs to the otherwise inert lamps.

Now in a pinch, this project could have been done with nothing more than some coin cells and a suitably sized LED. But seeing as the lamp posts were clearly designed in the Victorian style, [Braden] felt they should softly flicker to mimic a burning gas flame. Blinking would be way too harsh, and in his own words, look more like a Halloween decoration.

This could have been an excuse to drag out a microcontroller. But instead, [Braden] did as any good little Hackaday reader should do, and called on Old Saint 555 to save Christmas. After doing some research, he determined that a trio of 555s rigged as relaxation oscillators could be used to produce quasi-random triangle waves. When fed into a transistor controlling the LED, the result would be a random flickering instead of a more aggressive strobe effect. It took a little tweaking of values, but eventually he got it locked down and sent away to have custom PCBs made of the circuit.

With the flicker driver done, the rest of the project was pretty simple. Since the lamp posts were already hollow, feeding the LEDs up into them was easy enough. The electronics went into a 3D printed base, and we particularly liked the magnetic connectors [Braden] used so that the lamps could easily be taken off the base when it was time to pack the village away.

We can’t wait to see what new tricks [Braden] uses to bring the village alive for Christmas 2025. Perhaps the building lighting could do with a bit of automation?

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A Vintage Single Transistor LED Blinker

October 17, 2016 by Rich Hawkes 19 Comments

[Eric Wasatonic] had a box of SWB2433 transistors that he had very little information about. In order to discover their properties, he fired up his curve tracer to compare these transistors with more common ones. He noticed the SWB2433 exhibited negative resistance while the similar curves of a 2n3904 didn’t. Then he reverse-biased the two transistors: the negative resistance region on the 2n3904 was less than that of the SWB2433, but it was there, and a 2n2222 had a bigger region. Using this knowledge, he developed a relaxation oscillator circuit which uses a negatively biased transistor.

Using one transistor, one resistor and one capacitor, he describes the circuit and how the components affect the frequency of the sawtooth wave the oscillator creates. [Eric] uses the oscillator to build a simple LED blinker and shows what happens when he changes the transistor and adjusts the voltage or resistance. He also shows the circuit as a tone generator and adjusts the tone by replacing the resistor with a potentiometer. And then, for fun, he modifies the circuit to show the oscillator as an AM transmitter. Check out his video after the break.

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Analog Drum Machine

December 17, 2013 by Eric Evenchick 11 Comments

This analog drum machine project synthesizes a kick and snare drum that are clocked to a beat. It pulls together a few analog circuits to do the timing and synthesis.

The beat timing is a product of a hysteretic oscillator used to create a ‘shark wave,’ which is a friendly term for the output of a relaxation oscillator. This waveform can be compared to a set point using a comparator to create a slow square wave that clocks the drum beat.

The kick drum is synthesized using another hysteretic oscillator, but at a higher frequency, creating a triangle-like waveform at 265 Hz that provides a bass sound. The snare, however, uses white noise provided by a BJT’s P-N junction, which is reverse biased and then amplified. You can spot this transistor because its collector is not connected.

The resulting snare and kick drum wave forms are gated by two transistors into the output. Controlling these gates allows the user to create a drum beat. After the break, check out a video walk-through and a demo of the build.

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