Arduino Hacks

3039 Articles

Panel Mount Display Solves The Problem Of Drilling Square Holes

March 17, 2017 by 33 Comments

[Absolutelyautomation] has a problem with seven-segment displays. Fitting these displays in an enclosure is a pain because you can’t drill perfectly square holes, and you will invariably mess up a few enclosures with overzealous file work. There is a solution to this problem – panel mount meters.

The bezels on these panel mount meters hide the imperfections in the enclosure, and usually don’t require screws. They are, however, dedicated displays, usually for temperature, RPM, or some other measurement.

[Absolutelyautomation] took one of these dedicated panel mount displays and turned it into an all-purpose device. Basically, it’s a panel mount Arduino with three seven-segment displays.

This project is built on perfboard cut down to fit inside the enclosure of a very cheap panel meter found at the usual suppliers. Tucked away underneath this perfboard is an ATmega, a few resistors, and the support parts to make everything go. This panel mount meter can either be a serial slave or as a standalone controller, programmable with the Arduino IDE. It’s cheap, too. You can check out [Absolutelyautomaion]’s video below.

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The Custom Clicky Shortcut Keypad

March 17, 2017 by 37 Comments

You’re not cool unless you have a mechanical keyboard. Case in point: if you were to somehow acquire an identical keyboard to the one I used to type this, it would set you back at least seven hundred dollars. Yes, it’s mechanical (Topre), and yes, I’m cooler than you. Of course, you can’t be as cool as me, but you can build your own mechanical keyboard. [Robin] is, I presume, a pretty cool dude so he built his own keyboard. It’s the amazing shortcut keyboard, and it can be programmed graphically.

The idea for this keyboard came when [Robin] was studying as an engineer. We assume this is code for wearing out the Escape key on AutoCAD, but many other software packages have the same problem. The solution to [Robin]’s problem was a shortcut keypad, a 3 by 4 matrix of Cherry switches that could be programmed for any task.

The design of this keyboard started out as an Adafruit Trellis matrix keypad. This was combined with some software written in Processing that assigned macros to each button. This was a sufficient solution, but the switches in the Adafruit trellis look squishy. These are not the right switches for someone who craves a soft snap under every fingertip. It’s not the keyboard of someone who desires the subtle thickness of laser etched PBT keycaps. The Adafruit keypad doesn’t have the graceful lines of a fully sculpted set of keycaps. Oh my god, it’s doubleshot.

[Robin]’s completed keyboard has gone through a few revisions, but in the end, he settled on PCB-mounted switches and a very clever 3D printed standoff system to hold an Arduino Pro Micro in place. The enclosure, too, is 3D printed, and the end result is a completely custom keyboard that’s perfect for mashing key combos.

You can check out a video of this keyboard in action below.

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The Altair Shield

March 14, 2017 by 24 Comments

From PDPs to Connection Machines, the Hackaday crowd are big fans of blinkenlights. While this project isn’t an old CPU, RAM, ROM, and an S-100 bus wrapped up in a fancy enclosure, it is a great recreation of the Altair 8800, the historic kit computer that supposedly launched the microcomputer revolution.

[Justin] says his project is just another Altair 8800 clone, but this one is cut down to the size of an Arduino shield. This is in stark contrast to other Altair recreations, whether they are modern PCs stuffed in an old case, modern replicas, or a board that has the same functionality using chunky toggle switches.

On board [Justin]’s pocket-sized Altair are a few LEDs, some DIP switches, and an octet of spring-loaded dual throw switches that wouldn’t look out of place in a 40-year old computer.

This shield targets the Arduino Due rather than the Mega, but only because the Due performs better running an Altair simulation. Everything is there, and a serial terminal is available ready to run BASIC or any other ancient OS.

Pulse Oximeter Is A Lot Of Work

March 11, 2017 by 24 Comments

These days we are a little spoiled. There are many sensors you can grab, hook up to your favorite microcontroller, load up some simple library code, and you are in business. When [Raivis] got a MAX30100 pulse oximeter breakout board, he thought it would go like that. It didn’t. He found it takes a lot of processing to get useful results out of the device. Lucky for us he wrote it all down with Arduino code to match.

A pulse oximeter measures both your pulse and the oxygen saturation in your blood. You’ve probably had one of these on your finger or earlobe at the doctor’s office or a hospital. Traditionally, they consist of a red LED and an IR LED. A detector measures how much of each light makes it through and the ratio of those two quantities relates to the amount of oxygen in your blood. We can’t imagine how [Karl Matthes] came up with using red and green light back in 1935, and how [Takuo Aoyagi] (who, along with [Michio Kishi]) figured out the IR and red light part.

The MAX30100 manages to alternate the two LEDs, regulate their brightness, filter line noise out of the readings, and some other tasks. It stores the data in a buffer. The trick is: how do you interpret that buffer? Continue reading “Pulse Oximeter Is A Lot Of Work” →

Save ESP8266 RAM With PROGMEM

March 10, 2017 by 21 Comments

When [sticilface] started using the Arduino IDE to program an ESP8266, he found he was running out of RAM quickly. The culprit? Strings. That’s not surprising. Strings can be long and many strings like prompts and the like don’t ever change. There is a way to tell the compiler you’d like to store data that won’t change in program storage instead of RAM. They still eat up memory, of course, but you have a lot more program storage than you do RAM on a typical device. He posted his results on a Gist.

On the face of it, it is simple enough to define a memory allocation with the PROGMEM keyword. There’s also macros that make things easier and a host of functions for dealing with strings in program space (basically, the standard C library calls with a _P suffix).

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Arduino Into NAND Reader

March 10, 2017 by 31 Comments

[James Tate] is starting up a project to make a “Super Reverse-Engineering Tool”. First on his list? A simple NAND flash reader, for exactly the same reason that Willie Sutton robbed banks: because that’s where the binaries are.

As it stands, [James]’s first version of this tool is probably not what you want to use if you’re dumping a lot of NAND flash modules. His Arduino code reads the NAND using the notoriously slow digital_read() and digital_write() commands and then dumps it over the serial port at 115,200 baud. We’re not sure which is the binding constraint, but neither of these methods are built for speed.

Instead, the code is built for hackability. It’s pretty modular, and if you’ve got a NAND flash that needs other low-level bit twiddling to give up its data, you should be able to get something up and working quickly, start it running, and then go have a coffee for a few days. When you come back, the data will be dumped and you will have only invested a few minutes of human time in the project.

With TSOP breakout boards selling for cheap, all that prevents you from reading out the sweet memory contents of a random device is a few bucks and some patience. If you haven’t ever done so, pull something out of your junk bin and give it a shot! If you’re feeling DIY, or need to read a flash in place, check out this crazy solder-on hack. Or if you can spring for an FTDI FT2233H breakout board, you can read a NAND flash fast using essentially the same techniques as those presented here.

Arduino + Geometry + Bicycle = Speedometer

March 9, 2017 by 9 Comments

It is pretty easy to go to a big box store and get a digital speedometer for your bike. Not only is that no fun, but the little digital display isn’t going to win you any hacker cred. [AlexGyver] has the answer. Using an Arduino and a servo he built a classic needle speedometer for his bike. It also has a digital display and uses a hall effect sensor to pick up the wheel speed. You can see a video of the project below.

[Alex] talks about the geometry involved, in case your high school math is well into your rear view mirror. The circumference of the wheel is the distance you’ll travel in one revolution. If you know the distance and you know the time, you know the speed and the rest is just conversions to get a numerical speed into an angle on the servo motor. The code is out on GitHub.

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