Hacklet 70 – Calculator Projects

Hackers, makers, and engineers have long had a love affair with number crunching. Specifically with the machines that make crunching numbers easier. Today it may be computers, smart watches, and smartphones, but that wasn’t always the case. In the 50’s and 60’s, Slide rules were the rage. Engineers would carry them around in leather belt pouches. By the early 70’s though, the pocket calculator revolution had begun. Calculators have been close at hand for hackers and engineers ever since. This week’s Hacklet celebrates some of the best calculator projects on Hackaday.io!

calc1We start with [Joey Shepard] and RPN Scientific Calculator. No equals sign needed here; [Joey] designed this calculator to work with Reverse Polish notation, just like many of HP’s early machines. Stacks are pretty important for RPN calculators, and this one has plenty of space with dual 200 layer stacks. The two main processors are MSP430s from Texas Instruments. The user interface are a 4 line x 20 character LCD and 42 hand wired buttons. The two processors are pretty ingenious. They communicate over a UART. One processor handles the keyboard and display, while the other concentrates on crunching the numbers and storing data in an SRAM. The case for this calculator is made from soldered up copper clad board. It’s mechanically strong especially since [Joey] added a bead of solder along each joint. If you want to learn more about this technique check out this guide on FR4 enclosures.

[Joey] definitely improved his solder skills with this project. Every wire and connection, including the full SRAM address and data bus were wired by hand on proto boards. We especially like the sweet looking laser cut keyboard on this project!
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Trinket EDC Contest Winners

It’s time to announce the winners of the Trinket Everyday Carry Contest! We’ve had a great 5 weeks watching the projects come together. A team of Hackaday staffers spent their weekend watching videos and selecting their top entries based on the contest rules. We had a really hard time picking the top three – the competition was tight, and there were quite a few awesome projects.

Without further ado, here are the winners!

1337toolFirst Prize: 1337 3310 tool. [Mastro Gippo] really knocked this one out of the park. He built a swiss army knife of a tool out of the iconic Nokia 3310 candybar phone. 1337 3310 tool is a graphing voltage and current meter, an ohmmeter, a continuity tester that plays the original Nokia ringtone, and a gaming machine which can play Tetris.  [Mastro Gippo] is 99% there with TV-B-Gone functionality as well. Amazingly, [Mastro Gippo] kept the Nokia look and feel in his user interface. He spent quite a bit of time grabbing data and bitmaps from the 3310’s original ROM.  [Mastro Gippo] is getting a Rigol DS1054Z scope to help iron out the bugs in his future projects!

pavaproSecond Prize: Pavapro – portable AVR programmer. [Jaromir] built an incredible pocket-sized microcontroller programming tool. Pavapro can read and edit text files, handle serial I/O at 9600 baud, and burn AVR microcontrollers. If that’s not enough, it can actually assemble AVR binaries from source. That’s right, [Jaromir] managed to fit an entire assembler on the Pro Trinket’s ATmega328 processor. Pavapro’s 16 button keypad won’t allow for much in the way of touch typing, but it does get the job done with T9 style text entry. The device is also extensible, we’re hoping [Jaromir] adds a few other architectures! PIC and MSP430 modes would be awesome!  [Jaromir] will be receiving a Fluke 179 multimeter with a 6 piece industrial electronics tip kit! We’re sure he’ll put it to good use.

robohandThird Prize: Robotic 3rd Hand. Let’s face it. We can’t all be Tony Stark. But [Tim] gets us a little bit closer with his awesome wearable entry. Need a tool? Just press the button, and Robotic 3rd Hand will give you a … hand. [Tim’s] creation utilizes the Pro Trinket to drive a servo which moves an incredibly well designed and 3D printed mechanism that lifts a screwdriver off the wearer’s wrist and places it into their hand. [Tim] originally was going to go with Electromyography (EMG) sensors to drive the hand, however he switched to a simple button when they proved problematic. We absolutely think this was the right decision for the contest – it’s always better to have a simpler but working project rather than a complex yet unreliable one. That said, we’d love to see him circle back and give EMG another try! [Tim’s] next project will be soldered up with the help of a Hakko FX888D with a tip kit. If things get a bit wobbly, he can use his new Panavise 324 Electronic Work center to keep everything steady.

If you didn’t make the top three in this contest, don’t give up! We’re going to be having quite a few contests this year. The top 50 entrants will receive custom Hackaday EDC Contest T-shirts. Check out the full list of 50 on Hackday.io!

Trinket EDC Contest – The Deadline Approaches

We’ve got just under 2 days left in the Trinket Everyday Carry Contest. With 79 entries, and t-shirts going to the top 50 entrants, you’ve got pretty darn good odds of getting a shirt out of all of this! The design is great too, [Joe Kim] really did a great job with it!



The idea is simple: Build small, pocketable projects which are useful everyday.

We explained everything in our announcement post, and the full rules are available on the contest page. But just as a reminder, the main requirements are

  • The project Must use a Pro Trinket, or a board based on the open source Pro Trinket design.
  • The project must have at least 3 project logs
  • The project must have at least one video
  • The Hackaday.io project must include enough documentation to allow an average hobbyist to replicate the project

There are already some awesome entries vying for the top prize, but who knows – someone may come out of nowhere and walk away with a sweet Rigol ds1054z oscilloscope!


The contest deadline is January 3rd, at 12:00 am PDT. The clock is ticking, so stop waiting, and go build something awesome! Good luck to everyone who enters!

Announcing The Trinket Everyday Carry Contest

Now that we’ve recovered from our Munich party and the awarding of The Hackaday Prize, we’re ready to announce our latest contest. We’ve been having a lot of fun with our Trinket Pro boards, both the 10th anniversary edition and the new Hackaday.io branded models.  While we were soldering, compiling, and downloading, a contest idea took root. Trinket Pro really excels when used in small projects, the kind which would fit in a pocket. To that end we’re holding the Trinket Everyday Carry Contest, a showcase for small, pocketable projects which are useful everyday. ‘Useful everyday’ is a bit of a broad term, and we intended it that way. Tools are useful of course , but so are jewelry pieces. It’s all in the eye of the builder and users. We’re sure our readers will take this and run with it, as they have with our previous contests.

There are some great prizes in store for the entrants, including a brand new Rigol DS1054Z  oscilloscope! The top 50 entrants will get custom Trinket Everyday Carry Contest T-shirts. Check out the contest page for a full list. 

submit-project-to-trinket-edcWe know you all love to procrastinate with your entries, so we’re going to be offering a few perks to those who enter early and update often. Each week, we’ll throw all the entrants who have published at least one project log full of details into a drawing for a special prize from The Hackaday Store. To be considered you must officially submit your project which is accomplished through a drop-down list on the left side of your project page.

Remember, the contest isn’t just about winning a scope, a meter, or any of the other prizes. It’s about creating new Open Hardware designs that nearly anyone can build. So grab those soldering irons, load up those copies of the Arduino IDE, AVR-GCC, or WinAVR, and get hacking!

You can view the all of the contest entries in this list.

Gaming system inside an Atari joystick


This original Atari controller is pretty small (take a look at that RCA cable for a sense of scale). Despite it’s size, [Kyle Brinkerhoff] managed to fit a complete gaming system inside the controller. This Pocket Sized Atari is a follow-up to another project he did called ArduPong which let him play Pong using a joystick and an Arduino. This rendition takes the external project box from that build and moves everything into one tight little package.

In the video after the break [Kyle] gives us a tour of the internals. The Arduino board he went with is an Ardweeny which is no bigger than the ATmega328 footprint so it can be easily mounted off to one side. The joystick internals have been replaced with the analog stick module from a PlayStation controller. That is where the button came from as well. Just connect this to a 9V battery and the composite video input of a TV and you’re ready to do some gaming!

Now if you just want that retro look for your Xbox Live games check out this Xbox 360 controller in an Atari joystick.

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Homemade music player

Sadly, this pocket mp3 wav player doesn’t come close to the capabilities of even an iPod generation 1 yet, but you have to give [Owen] props for making it in less than 24 hours. The system consists of a Propeller MCU (cleverly wired to be swappable with “shields” similar to Arduino systems), SD card for song storage, and an LM386 for audio. While the setup is a little dull, and only plays through songs non stop with no controls whatsoever, it certainly is a good start in the right direction for a cheap and simple portable music player. Of course some planned changes are in the works, include an accelerometer (gesture based controls?), etched PCB, docking station, and a case. We’re surprised there is no form of screen planned, considering Owen appears to have a rather good handle on touch interfaces; perhaps he’s waiting for revision 3.

LED Pocket Watch


Today, it is not difficult to find all kinds of watches with LED displays. After [Paul]’s grandfather, a master horologist and pocket watch collector, passed away, he decided to retrofit a broken watch left to him with a custom LED face. Starting from scratch, he designed a PCB complete with 133 (hand soldered) LEDs, room for a temperature controlled oscillator for real time clock capabilites, a LiPo battery, and a cell phone vibrator to provide a simulated “second hand tick” feeling. The whole watch is powered by a PIC 16F946.

This is currently version 1, and he has already begun work on version 2. He plans on adding a more compact, lower power TCXO, automatic NTP syncing, and a USB port for charging and reprogramming. He has a number of detailed videos, and we have a demo video after the break.

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