As I wrote in my column Ode to a 555 Timer: “When you are an electronics engineer, some numbers cry out to you when you hear them, like 4004 (the world’s first commercial microprocessor chip) and 8051 (if not the first, then certainly one of the most beloved of the early microcontrollers).”

Three Fives Kit (Click image to see a larger version — Image source: EvilMadScientist)

I went on to say, “And, of course, one number that makes all of our ears prick up is 555. This was the number assigned to the Signetics Timer integrated circuit (IC), which was designed by Hans R. Camenzind in 1971 and released to the market in 1972. Comprising 25 transistors, two diodes, and 15 resistors, and utilizing some clever design techniques — such as replacing an external constant-current source with a direct internal resistance — Hans managed to squeeze the 555 into an eight-pin package.”

The funny thing about the 555 is that — even though it’s close to 50 years old — it manages to keep on merrily trucking away, both in designs and in the popular imagination (well, the popular imagination of those of an engineering bent). Take, for example, the Evil Mad Scientist’s Three Fives Kit, which is a functional replica of the classic NE555 timer constructed using discrete transistors and resistors (in the image presented here, a real 555 chip is shown for comparison). There’s also the 555 Footstool, which is a bit corny (pun intended).

The reason I mention all of this here is that my chum James “Chewy” Vroman just sent me a link to an overkill vacuum tube implementation of a 555 timer project on This little beauty was created by David Lovett (a.k.a. Usagi Electric). I just went on David’s YouTube Channel to discover all sorts of interesting things, including a 1-Bit Breadboard Computer along with this video of the 555 vacuum tube timer.

I must admit that I initially misread the “Bunny for Scale” as being “Bunny for Sale,” but then I realized my mistake and hopped to it.

As the text accompanying the video says: “The 555 Timer is one of the most important and prolific integrated circuits of all time. They’re incredibly cheap, can be sourced from nearly anywhere and work wonderfully. So, let’s make it markedly worse in every single aspect! It’s huge, it consumes a ton of power, it wasn’t cheap by any means, but it works!”

David is obviously a man after my own heart. I would love to have one of these “hollow state” 555 timers on my desk here in my office. Also, I’m thinking that we could find a role for one in our 4-Bit HRRG Computer project. How about you? Do you have any 555 timer-related tales you’d care to share with the rest of us?