Vintage VT100 terminal computing…with a Beaglebone

March 7, 2012 By Leave a Comment

decbox

A cool little project came our way, which we thought might be of interest to some of you vintage computer buffs. [Joerg Hoppe] wrote in to share a DEC VT100 terminal he resurrected in a novel fashion.

His “DECBox” system was created with a Beaglebone, which he uses to run a wide array of PDP11/VAX terminal emulators, thanks to the SIMH project. [Joerg] constructed an expansion shield for the Beaglebone that provides several UART connections, enabling him to connect it to his DEC terminal over a serial interface. Since he added several serial plugs to the Beaglebone, he can even run multiple emulator installations in parallel on different terminals without too much trouble.

[Joerg’s] efforts are mainly for a vintage computer display he is constructing, but setting up such a system of your own should be no problem. If you happen to have one (or more) of these boxes sitting around collecting dust, this would be an easy way to get them all up and running without bulky external hardware, since the Beaglebone tucks nicely into the rear expansion slot on a VT100.

Be sure to check out his site for more details on how his DECBox software package works as well as for more pictures of vintage terminal goodness.

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Loading programs onto a TRS-80 Model 100

March 5, 2012 By Leave a Comment

We’d guess that you don’t have a TRS-80 Model 100 computer sitting around. But we’ve heard that the decades-old hardware is built like a tank so if you search around you can probably get your hands on a working unit. The Model 100 boasted some nice features, one of which was a 300 baud modem allowing you to transfer data onto the device. [MS3FGX] wanted to give it a try but had to do some work to get the Model 100 to communicate with modern hardware.

This could have been a much more involved process, but since the Model 100’s modem uses common communications standards it’s really just a matter of hooking it up and choosing the right COM port settings on a computer. In this example a Linux box is used with the program Minicom. It is configured to communicate at 300 baud 8N1 (8 data bits, no parity bit, and one stop bit).

With software in place you’ll need to make your own cable. [MS3FGX] does this using a DB-25 connector for the Model 100 side, and a DB-9 connector for the serial port on the Linux box. He’s got a pin-out for the cable on the second page of his guide. It sounds like it should be no problem to use a USB-serial converter if you don’t have a serial port.

Once everything is in place you’ll be able to transfer BASIC programs from your computer to the Model 100.

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Antique phone provides a soundtrack perfect for restoring old cars

March 5, 2012 By Leave a Comment

crank-phone-music

[Simon] is in the middle of restoring/building himself an Austin 7 Special out in his garage, and like most tinkerers, found that music helps to move the process along. He happened to have an old Bakelite generator phone out in the garage as well, and figured that he might as well have it do something other than simply hang on the wall.

Playing music from the 1930 seemed like a fitting enough task, so he picked up an Adafruit Waveshield and spent some time wiring it up to the old telephone. His new radio works simply enough, piping .wav files through the handset, provided someone has cranked the phone’s generator recently.

While cranking the generator is required to play music, the Arduino is actually powered off a pair of AA batteries. The cranking is all cosmetic, but he did program the Arduino to slow the music down every once in awhile, requiring that the generator be turned to get things back up to speed.

It really is a neat way to repurpose the old phone, and we like the fact that [Simon] did not gut it to put this project together.

Continue reading to see a short video of his new music player in action.

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Auto power circuit for an arcade machine

March 1, 2012 By Leave a Comment

Some of the pinball machines which [Jeri Ellsworth] has restored have ended up in the break room at her work. We’re sure her coworkers are thankful for this, but sometimes they forget to turn off the power to the machines, and letting them run constantly means more frequent servicing will be necessary. She set out to fix the situation by building a circuit that will automatically power the machines.

We think the solution adds some much needed functionality. Instead of hunting for the power switch, you can now power the machine up by hitting the left flipper, and it will automatically shut off after about five minutes of not having that flipper button pressed. For this she grabbed a 555 timer chip and built a circuit to control the relay switching the mains power.

She added a magnet and reed switch to the left flipper switch assembly to control her add-on circuit. It connects to the base of a PNP transistor which controls a resistor network and capacitor. This part of the circuit (seen to the left of the 555 in the schematic) allows the timer to be re-triggered. That is, every time you press the flipper the 555 will reset the timer. Don’t miss the demo she filmed after the break.

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Semaphore signal replica perfect for the train buff in your life

February 29, 2012 By Leave a Comment

semaphore-signal

[John Philip’s] brother has a sizable room set aside for his model railroad setup, and he was looking for something interesting to add to his brother’s collection. Rather than construct something for the railroad itself, he decided that an early 1900’s-style semaphore railroad signal would make a great novelty item for the room.

The project started with [John] scouring the Internet for colored signal lenses. Once he found a set that worked for him, he crunched some numbers to ensure that the rest of the semaphore box stayed true to original scale. Inside the signal’s case you will find a small regulator board for his light source, an Arduino, and a motor controller board to actuate the arm.

To ensure that the signal arm is always perfectly positioned, he installed a pair of reed switches on either side of the case, enabling the Arduino to auto-calibrate the signal’s position each time it is powered on. At first, this control scheme might strike you as a bit over the top, but we really like the fact that the signal can always configure itself to function perfectly, even if someone tinkers with/bumps into/moves the arm at any point.

Be sure to stick around to see a short video of the semaphore signal in action.

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Visualizing a nanosecond

February 27, 2012 By Leave a Comment

We’re so glad to have run across this video where [Rear Admiral Grace Hopper] explains how to visualize a nanosecond. Now we had never heard of [Grace Hopper] before, but once you watch the clip (also embedded after the break) you’ll want to know who this person is. We work with divisions of seconds all the time when developing with microcontrollers. But those concepts are so abstract we never had a need to think about them as a physical distance. After all they’re a measure of time, right?

You can’t make it out, but she’s holding a length of wire between her hands. It is 11.8 inches long and represents how far electricity can travel in one nanosecond (one billionth of one second). She goes on to explain that this is a calculation of the distance which light can travel in one nanosecond, then really hits the concept home when she uses it to explain latency in satellite communications. For us, the waste of not putting a chip into sleep mode when it’s just stuck in the loop waiting for an interrupt is where we made the connection.

So back to the woman herself. We think you’ll really enjoy reading through her Wikipedia biography page. [Grace] was a computer science pioneer. She is credited with writing the very first computer compiler. She postulated and articulated the concepts that led to the development of COBOL, and popularized the term ‘debugging’. In short, she is one of the giants whose shoulders we all stand upon.

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