Day: February 19, 2018

Milspec Teardown: CP-142 Range Computer

February 19, 2018 by 69 Comments

As some of my previous work here at Hackaday will attest to, I’m a big fan of World War II technology. Something about going in with wooden airplanes and leaving with jet fighters and space capable rockets has always captivated me. So when one of my lovingly crafted eBay alerts was triggered by something claiming to be a “Navy WWII Range Computer”, it’s safe to say I was interested.

Not to say I had any idea of what the thing was, mind you. I only knew it looked old and I had to have it. While I eagerly awaited the device to arrive at my doorstep, I tried to do some research on it and came up pretty much empty-handed. As you might imagine, a lot of the technical information for hardware that was developed in the 1940’s hasn’t quite made it to the Internet. Somebody was selling a technical manual that potentially would have covered the function of this device for $100 on another site, but I thought that might be a bit excessive. Besides, where’s the fun in that?

I decided to try to decipher what this device does by a careful examination of the hardware, consultation of what little technical data I could pull up on its individual components, and some modern gear. In the end I think I have a good idea of how it works, but I’d certainly love to hear if there’s anyone out there who might have actually worked with hardware like this and could fill in any blanks.

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The White Rabbit Nixie Clock

February 19, 2018 by 20 Comments

Instructables user [hellboy] — a recent convert to the ways of the laser cutter — is a longtime admirer of Nixie tubes. In melding these two joys, he has been able to design and build this gorgeous work of art: The White Rabbit Nixie Clock.

Going into this build, [hellboy] was concerned over the lifespan of the tubes, and so needed to be able to turn them off when not needed. Discarding their original idea of having the clock open with servos, [hellboy]’s clock opens by pressing down on a bar and is closed by snapping the lid shut — albeit slightly more complicated than your average timepiece. Given the intricacy of the mechanism, he had to run through numerous prototypes — testing, tweaking and scrapping parts along the way.

With the power of steam-bending, [hellboy] lovingly moulded walnut planks and a sundry list of other types of wood to define the ‘rabbit’ appearance of the mechanism, and the other parts of the clock’s case. Once again, designing the clock around a row of six pivoting Nixie tubes was no mean feat — especially, as [hellboy] points out, when twenty or so wires need to rotate with them! After a few attempts, the Nixie tubes, their 3mm blue LEDs and associated wires were properly seated.

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Roll Your Own Rotary Encoders

February 19, 2018 by 36 Comments

[miroslavus] hasn’t had much luck with rotary encoders. The parts he has tested from the usual sources have all been problematic either mechanically or electrically, resulting in poor performance in his projects. Even attempts to deal with the deficiencies in software didn’t help, so he did what any red-blooded hacker would do — he built his own rotary encoder from microswitches and 3D-printed parts.

[miroslavus]’s “encoder” isn’t a quadrature encoder in the classic sense. It has two switches and only one of them fires when it turns a given direction, one for clockwise and one for counterclockwise. The knob has a ratchet wheel on the underside that engages with a small trip lever, and carefully located microswitches are actuated repeatedly as the ratchet wheel moves the trip lever. The action is smooth but satisfyingly clicky. Personally, we’d forsake the 3D-printed baseplate in favor of a custom PCB with debouncing circuitry, and perhaps relocate the switches so they’re under the knob for a more compact form factor. That and the addition of another switch on the shaft’s axis to register knob pushes, and you’ve got a perfectly respectable input device for navigating menus.

We think this is great, but perhaps your project really needs a legitimate rotary encoder. In that case, you’ll want to catch up on basics like Gray codes.

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