Mechanical Memory & Nixie Fun With BCD Switches!!!

Very interesting. There are some clever people in this world.

There are also hexadecimal versions of the switches which generate 0-F - all 16 values of 4 bits. Useful for inputting memory addresses and data bus values. crypto keys, too.

Mike O'Dell

These that I have are all closed to common when on 0...

Fran Blanche

Coincidentally, my (decimal) pushbutton switches just arrived today: https://imgur.com/a/e8AYTAr - they're smaller, daintier and the cutest things ever :)

horrovac

Wow... I have been looking for this type of switches in order to make me a resistor decade, but I found none and had to order some push-button ones. Also, the problem is that they have no "passthrough" for the value zero. For all the non-zero values you could just hook up X * 10ⁿ increments of X=1, 2, 4 and 8Ω, but for 0 it's open circuit, whereas I'd need a short circuit. I haven't figured out how I could implement this logic and obtain 0 ohm when 0 is dialed. So I had to order some decimal ones. Pity, it would have been a neat trick. Though, having watched the video: I'd probably be able to bodge a contact onto a 0 position and have a short circuit wire out. Are these available out of China?

horrovac

It is!

Fran Blanche

An eternal monument to one brave little switch.

Fran Blanche

And here I thought that 4 bits was fifty cents.

Rocco Rizzo

Yes, chisels! That's a great tip over using an X-cto knife for cutting something flush. I don't know how many times I've had an X-acto catch because the edge is at the wrong angle and the handle is light-duty aluminum. Also, those BCD switches are a small revelation. I'm always amazed how often my projects need the simplest and most basic functionality of choosing "a number" for some kind of input to the rest of the circuit, whatever it is (frequency generator, power supply, etc.). Using 7447s or 74145s or CA3161s is still an option but they are getting expensive, while the BCD function is really a simple conversion that can be done mechanically just fine. Thanks, Fran, for the tutorial.

Peter Knazko

One little BCD switch gave it's life in the name of science. An impressive modification to BigIron would be to attatch a small microphone to the transformer so you could amplify the mains hum so you could have and impressive woommmmm from it. OK so I'm a weirdo who likes to hang around substations. :-D

Dr Andy Hill

Nixies are my favourite type of display. Now I need to think of a project which needs BCD switches.

David Peaker

I really like this series of fast little topics

The thing I remember the most being mechanical numbers were gas pumps. Now they are all fancy digital flammable liquid dispensers.

John McCormick

Such a cool set up and demo Fran. Enjoyed ❤️

CRM114 stuff :)