Starting to Wrap Up Maker Faire

It’s almost a week since the NYC Maker Faire, and it’s about time for us to start wrapping up all the posts we’re doing on everything we’ve seen.

DSC_0216[Chris Mitchell], hackaday favorite from Cemetech did what he always does at Maker Faire: brought some stuff he’s doing with TI graphing calculators.

The TI-84 with GPS made a showing, as did the graphing calculator IRC client. By far the coolest looking calculator was the wooden casemod. It’s a TI-82 put into a (what feels and looks like) a maple enclosure. The buttons are painted on, and despite stuffing consumer electronics into a handmade case, it’s still reasonable portable.

DSC_0201There were more Hackaday fans at the faire, but I’m not sure if anyone can beat the guys from Protopalette. Wait. One guy could. Find me in public sometime and I’ll tell you about that.

The Protopalette is a board with a bunch of lights, buttons, switches, sensors, knobs, servos, and buzzers for electronics prototyping. Think of it as a stylized version of the old ‘parts and springs and wire’ radio shack beginner electronic kits.


Some of the members of the hackerspace with the craziest group narrative, LVL1 in Louisville, made it to the faire. They’re working with GE to create a ‘maker module’ for appliances. It’s called Green Bean, and GE is actually building support for this into some of their fridges, washers, stoves and dishwashers.

There are a few modules already, like a scale that will send out a message when you’re out of milk. It’s an interesting system, and there are already a lot of appliances that support the system.

Pics below.

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Retrotechtacular: The CURTA Mechanical Calculator

The CURTA mechanical calculator literally saved its inventor’s life. [Curt Herzstark] had been working on the calculator in the 1930s until the Nazis forced him to focus on building other tools for the German army. He was taken by the Nazis in 1943 and ended up in Buchenwald concentration camp. There, he told the officers about his plans for the CURTA. They were impressed and interested enough to let him continue work on it so they could present it as a gift to the Führer.

This four-banger pepper mill can also perform square root calculation with some finessing. To add two numbers together, each must be entered on the digit setting sliders and sent to the result counter around the top by moving the crank clockwise for one full rotation. Subtraction is as easy as pulling out the crank until the red indicator appears. The CURTA performs subtraction using nine’s complement arithmetic. Multiplication and division are possible through successive additions and subtractions and use of the powers of ten carriage, which is the top knurled portion.

Operation of the CURTA is based on [Gottfried Leibniz]’s stepped cylinder design. A cylinder with cogs of increasing lengths drives a toothed gear up and down a shaft. [Herzstark]’s design interleaves a normal set of cogs for addition with a nine’s complement set. When the crank is pulled out to reveal the red subtraction indicator, the drum is switching between the two sets.

Several helper mechanisms are in place to enhance the interface. The user is prevented from ever turning the crank counter-clockwise. The crank mechanism provides tactile feedback at the end of each full rotation. There is also a lock that disallows switching between addition and subtraction while turning the crank—switching is only possible with the crank in the home position. There is a turns counter on the top which can be set to increment or decrement.

You may recall seeing Hackaday alum [Jeremy Cook]’s 2012 post about the CURTA which we linked to. A great deal of information about the CURTA and a couple of different simulators are available at Make the jump to see an in-depth demonstration of the inner workings of a CURTA Type I using the YACS CURTA simulator.

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THP Entry: A Theatrical Lighting Controller Powered By A Calculator


Theatrical lighting usually runs with the help of DMX, a protocol that’s basically MIDI for lights; small, lightweight, ancient, and able to run on the lowest spec computers imaginable. For his Hackaday Prize entry, [Alex] figured a regular ‘ol graphing calculator was sufficient to run a complete DMX controller, and with the help of an Arduino, figured out a way to do it.

The hardware for the system consists of a TI-84 graphing calculator, a few bits and bobs in the way of components, and an Arduino Pro Mini powered from the USB port on the calculator. The Arduino handles the transmitting of DMX packets at 250 kbaud using the DMXSimple library over a 5-pin XLR jack.

The software running on the calculator is where the novel part of the project begins. The software is designed to be extremely lightweight, sending packets to the Arduino using the 2-wire link cable. DMX Commands are wrapped up and transferred using the TI-83/84 link protocol, decoded on the Arduino, and sent out to the lighting rig.

While this probably won’t replace the multi-thousand dollar lighting consoles found in theatres, it’s still a very handy and portable tool for debugging lights. It’s also [Alex]’s My First Electronics Project™, and a pretty good one at that.

SpaceWrencherThe project featured in this post is an entry in The Hackaday Prize. Build something awesome and win a trip to space or hundreds of other prizes.

Fixing A BASIC Calculator

HPThe early days of modern computing were downright weird, and the HP 9830B is a strange one indeed: it’s a gigantic calculator, running BASIC, on a CPU implemented over a dozen cards using discrete logic. In 2014 dollars, this calculator cost somewhere in the neighborhood of $50,000. [Mattis] runs a retrocomputer museum and recently acquired one of these ancient machines, and the walkthrough of what it took to get this old machine running is a great read.

There were several things wrong with this old computer when it arrived: the keyboard had both missing key caps and broken switches. The switches were made by Cherry, but no one at Cherry – or any of the mechanical keyboard forums around the Internet – have ever seen these switches. Luckily, the key cap connector isn’t that complex, and a little bit of bent wire brings the switches back up to spec. The key caps were replaced from a few collectors around the globe.

Getting as far as booting the machine, [Mattis] found some weirdness when using this old calculator: the result of 2+2 was 8.4444444, and 3+1 was 6.4444444. Simply pressing the number 0 and pressing execute resulted in 2 being displayed. With a little bit of guesswork, [Mattis] figured this was a problem with the ALU, and inspecting the ROM on that board proved to be correct: the first 128 nibbles of the ROM were what they were supposed to be, and the last 128 nibbles were the OR of the last half. A strange error, but something that could be fixed with a new replacement ROM.

After hunting down errors with the printer and the disk drive, [Mattis] eventually got this old calculator working again. For such an astonishingly complex piece of equipment, the errors were relatively easy to hunt down, once [Mattis] had the schematics for everything. You can’t say that about many machines only 10 years younger than this old calculator, but then again, they didn’t cost as much as a house.

Papercraft dial is the slide-ruler of current limiting resistors


This paper dial makes selecting current limiting resistors a snap. [Giorgos Lazaridis] came up with the tool, which he describes in detail in the Worklog tab of his writeup. If you want one of your own he also posted a PDF which you can print, cut, and tack together.

At this point we can calculate resistor values for LED circuits without looking at reference material. But it wasn’t always like that. This wheel will be a fantastic tool for those just starting out in hobby electronics who are trying to grasp the theory behind lighting up a simple project. The outer wheel references the source voltage, with the inner being a gauge of forward voltage across the LED(s). Line those two values up and you can read the optimal resistor value in the window seen to the right. But wait, there’s more! As you can see in the video after the break the opposite face of the dial also includes a window which will tell you the power dissipation so that you may choose a properly rated resistor. Slick!

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7400 Logic Competition winners announced

The 7400 Logic Competition has drawn to a close. The winners were announced and there are quite a few of them. There were fifteen first place winners named, nine second place, and nineteen third place projects. The bounty of quality entries is a testament to the popularity of the contest. It helps to have a wide range of prizes and the post linked above lists all of the sponsors who donated goodies as an incentive.

The board seen above was awarded the reader’s choice, to which the grand prize was awarded. It is a 7400 series calculator. [Umair Mukati] and [Naveed Ahmed] — both are students at the Institute of Industrial Electronics Engineering in Karachi, Pakistan — developed the device as part of a class project. It is capable of adding or subtracting two digit numbers. This includes support for negative numbers as results. We’ve embedded a video demo of the calculator in action after the break.

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Giving graphing calculators a new life

[Christopher] at Cemetech, ever frequent HaD feature for his hacked up graphing calculators, made it to the NYC Maker Faire.

He already posted on his blog he was making the trip up to Maker Faire, but we were lucky enough to catch up with him. Two things: the name of his blog isn’t ‘cement tech’, but ‘chem tech.’ Apparently he hates it when it’s mispronounced.

Secondly, he’s been turning in the TI-83s for a Casio Prizm graphing calculator. In the video above he tells us he’s gotten a few homebrew games running on the Prizm, a Lua interpreter, and is currently working on digging around the operating system.