Tag Archives: James Hobson

Catching drops of water with an ATmega48P

Drops of water are often captured in perfectly timed photographs with the help of an optointerrupter, light source and air gap flash.

As HackADay’s James Hobson notes, this configuration is typically expensive or difficult to put together.

Fortunately, a Maker by the name of Michal has come up with a viable alternative using an array of LEDs to illuminate the drops.

“He [uses] a IR diode, a photo-resistor, a few spacers, some plastic and a bunch of hot glue to make up his optointerrupter. When the droplet passes through the IR beam it breaks the signal from the photo-resistor which then triggers his Atmel ATmega48P [MCU],” says Hobson.

“It waits 80 milliseconds and then turns on the LEDs for approximately 50 microseconds. Meanwhile, [the Canon] camera is watching the whole event with a shutter-speed of a few seconds.”

As Michal explains in a detailed blog post, one of the nice things about using an LED configuration is that it boasts rise and fall times considerably shorter than traditional camera flash, which lights up for approximately 1-2 milliseconds, rather than 50 microseconds.

“That’s why most of the motion-stopping photography relies on more exotic air-gap flash units,” Michal concludes.

Interested in learning more? You can check out the project’s official page here.

Reading paper ticker tapes with an Arduino

Ticker tape – in use from 1870-1970 – was the earliest digital electronic communications medium, transmitting stock price information over telegraph lines.

According to Wikipedia, it consisted of a paper strip that ran through a machine called a stock ticker, which printed abbreviated company names as alphabetic symbols followed by numeric stock transaction price and volume information.

Recently, a Maker named NeXT decided to design a custom PCB from scratch to facilitate the easy reading of paper ticker tape. As HackADay’s James Hobson notes, it is somewhat difficult to buy a working paper tape reader at a reasonable price.

“What we love about this hack is its clever reuse of perfboard — it just so happens that the spacing of his paper tape holes line up perfectly with the holes in the perfboard. Don’t you love it when engineers work together with nice, even, standard units?” Hobson writes.

“After discovering this it was just a matter of adding some photo-transistors on one side of the perfboard sandwich and LEDs on the other side. A bit of soldering, some Schmitt triggers, and an Arduino Pro Mini [Atmel ATmega168 MCU] later… and bam you have a serial output of data.”

According to NeXT, the the output can be fixed to any specific baud rate, although it is currently set at a cool 9600.

“That’s enough that I won’t overflow the serial channel, nor will it be painfully slow. It’s possible that I can change the baud rate with a jumper but I’ve yet to learn how exactly that would be programmed so we’ll leave that for another day. When I want to reprogram it the same four pin header that powers it and connects it to the host also holds an Rx pin so I can talk to it,” he says.

“In the end I decided while this makes a very nice and portable reader I decided the best home would be in my DEC LA-120 hard copy terminal. It has an option knockout on one side and you could easily build it into the overall terminal by taking the Tx line from the reader and tapping into the TxD line on the terminal’s serial port. That way so long as you were in 9600 baud mode if you wanted to read in a paper tape you threaded it through the optic block, set the computer to capture through the serial port and then pulled the tape through.”

Interested in learning more? You can check out the project’s official page here.

How to build an Uno-based 3D scanner

Till Handel (aka alicedownthecoffeepot) has published a detailed paper describing how to build a relatively inexpensive 3D scanner using an Atmel-based (ATmega328 MCUArduino Uno board and assorted spare parts, such as those scavenged from old printers and laptops.

As HackADay’s James Hobson reports, the Uno-equipped platform is capable of scanning 360° around itself at distances from 0.3 – 5m, making it a perfect fit for scanning rooms.

“It uses a line laser and a webcam mounted on an arm driven by a stepper motor, which looks like it’s out of an old optical drive,” Hobson explains.

“[Meanwhile], an Arduino Uno and an A4988POW stepper driver control the system.”

According to Hosbon, Handel’s 3D scanner is similar to others on the market, with a line laser providing a 2D profile/outline of the object being scanned that the camera picks up.

“As the system (or object) rotates, new profiles are recorded and sewn together to form a complete 3D image,” says Hobson.

“To increase the resolution and accuracy of the scanner, you can always [use] a better camera.”

Interested in learning more? You can check out Till Handel’s blog post here and detailed paper (published under GPLv3) here.

Video: This giant LED Tamagotchi hearts Atmel

The Tamagotchi (たまごっち?) is a handheld digital pet, originally designed in Japan by Akihiro Yokoi of WiZ and Aki Maita of Bandai way back in 1996. According to Wikipedia, well over 76 million Tamagotchis have been sold world-wide.

Image Credit: Wikipedia

The majority of Tamagotchis are housed in a small egg-shaped computer with an interface (typically) consisting of three buttons, although the number of buttons may vary.

However, a Maker by the name of Vadim recently decided to create a unique, desktop-sized Tamagotchi using a spare LED matrix and an Atmel ATmega328P microcontroller (MCU) with an Arduino bootloader.

As HackADay’s James Hobson reports, the LED matrix comprises four 8×8 LED modules with four shift registers (74HC595) and two Darlington transistor arrays to take the current.

“This is because the 256 LEDs need to be multiplexed down to 32 IO’s (16 rows + 16 columns),” he explained.

After the hardware was deemed operational, Vadim started work on the coding side of things, writing the entire game from scratch.

“While it’s not that complex it’s still an impressive amount of effort that went into this desktop- sized Tamagotchi!” Hobson added.

Interested in learning more? You can check out the project’s official Instructables page here.

Uno power this two-axis solar tracker

Back in 2011, Jay Doscher had his power unexpectedly cut for 12 hours. After dealing with a refrigerator full of spoiled food, flashlights with dead batteries and a lack of candles, Doscher decided he needed to be better prepared for the next time the electricity went out.

His goal? To build a fully automated, portable solar tracking unit capable of automatically following the sun to optimize solar collection for those inevitable off-the-grid days.

As HackADay’s James Hobson notes, two-axis solar tracking units can help increase daily output by approximately 30%.

“Doscher’s makes use of a 12V gear reduced motor to provide panning and a linear actuator with positional tracking to control the tilt. To track the sun he’s got a digital compass and an Adafruit Ultimate GPS breakout board,” Hobson explained.

“To control it all he’s using is an [Atmel-powered] Arduino Uno (ATmega328 MCU). It’s a very slick and well engineered system and [Jay’s] hoping to spread it around the world — the entire thing is open source.”

Interested in learning more? You can check out Doscher’s tracker build log here and the relevant files on his GitHub repository here.

Video: Mega + Uno drives this 8X8X8 cube invader

Anred Zynch recently debuted a massively slick 8x8x8 LED cube — configured as a Space Invaders style game with a Playstation 1 controller.

According to Hackaday’s James Hobson, the cube is powered by an Arduino Mega (ATmega2560) which is tasked with driving the 512-LED array. 

Meanwhile, an Arduino Uno (ATmega328) is responsible for generating sound effects during gameplay.

Aside from the two Atmel based Arduino boards, key cube components include:

  • 512x LEDs
  • 10x Silver plated wire 0.8mm for sinkers and LED grid
  • 2x Breadboard 160×100 H25PR160 (sinkers)
  • 1x 100 Ohm resistor
  • 1x Speaker 8 Ohm
  • 2x resistor between 1,5 K and 47 K
  • 1x switch 2 or 3-positions
  • 1x or 2x 10K ohm resistor

Zynch’s cube — recently surfaced on Instructables — was reportedly inspired by a number of cube projects, including Chr’s and yes, the Borg cube by Das-Labour.

Interested in learning more? You can find additional information, along with a full parts breakdown on the project’s official page here.

DIY curved display with an Arduino Mega

A Maker by the name of Marin Davide has designed a DIY curved display with an Atmel-powered Arduino Mega (ATmega1280), nichrome wire and thermochromic liquid crystal ink.

According to James Hobson of HackADay, the current prototype uses a sheet of plastic coated in thermochromic ink – curved on an MDF frame.

“To display digits, Davide created tiny segments of the 7-segment display by wrapping the nichrome wire around pieces of cardboard, which then have been glued to the back of the display,” Hobson explained.

Meanwhile, Davide noted that although the prototype shows a 7-digit display, the detailed build guide can be easily modded to create a small dot-matrix display.

“The working prototype uses a sheet material printed with thermochromic liquid crystal ink,” Davide wrote in an official Design News description.

“It changes color (bright blue) when heated above 27C. Nickel-chrome wire is used to heat the segments and everything is controlled by an Arduino Mega board.”

The DIY curved display was made with 4mm Mdf, cut with a CNC, although this can also be done by hand. In addition, Davide used a 24V DC power supply, converted to 20Vdc with a KIA7820A. A 1000uF capacitor reduces noise on the 24V line, while a 220uF reduces noise on the 20V line. Last, but certainly not least, the Atmel-based Arduino is USB powered from the PC.

Interested in learning more about building a DIY curved display with an Atmel-based Arduino Mega? You can check out HackADay’s coverage here, the Design News article here and a detailed build tutorial (PDF) here.

Measuring capacitance

 with an Arduino Uno

Capacitance is typically defined as the ability of a body to store an electrical charge. More specifically, any object that can be electrically charged exhibits capacitance.

 A multimeter or multitester, also know as a VOM (Volt-Ohm Meter) can be used to measure the capacitance of a capacitor, but what if you don’t have one handy?

As it turns out, capacitance can be measured with an Atmel-based Arduino Uno (ATmega328) – sans external components and only ~20 lines of code. 

A blog post, written by Jonathan Nethercott that was recently featured on HackADay, explains how.

“[He] does an excellent job explaining a capacitance test circuit which uses a reference capacitor to calculate the unknown capacitance,” writes HackADay’s James Hobson. 

”He further explains that, with the Arduino Uno, you can remove the reference capacitor from the circuit, and simply use the stray capacitance present in the board and microcontroller, which can be calculated.”

Meaning, creating a test circuit is as simple as plugging in a capacitor to pins A0 and A2. On the software side, Nethercott’s code sense a 5V pulse to the capacitor – measuring the voltage on the other side, looping every half second and outputting the data onto a chart.

Nevertheless, as HackADay’s Hobson notes, the above-mentioned technique does require some calibration, with Jonathan measuring a known capacitor for a baseline and using the confirmed data to calculate the stray capacitance in the Arduino. 

Once accurately calibrated, users can typically achieve a resolution of approximately 1% for capacitors between 3.5pF and 225pF and around 5% for capacitors between 0.5pF and 1300pF.

Interested in learning more about how you can macgyver your Arduino Uno to measure capacitance? You can check out Jonathan Nethercott’s detailed blog post here.

A retro modern Nixie clock with Atmel’s ATmega48

As we’ve previously discussed on Bits & Pieces, there really is nothing quite like the comforting glow of a Nixie tube. Reboots apparently couldn’t agree more, as the retro modern Nixie clock he designed clearly illustrates.

According to HackADay’s James Hobson, Reboots was inspired to build the clock after coming across an old General Electric battery charger for sale.

“The Nixie tubes he chose for the project came from a lot sale on eBay, Russian surplus IN-12 tubes. He even managed to find an English datasheet for them,” Hobson explained.

“Having decided on the Nixie tube, driver, and case, he now needed a reliable power supply. Threeneuron’s design fit the bill nicely, however it ended up being a bit noisy under load, but the TubeClock kit used a free-running transistor oscillator, which was in fact even louder under load.”

From there, said Hobson, it was a matter of testing the tubes, prototyping PCBs and programming Atmel’s stalwart ATmega48 microcontroller (MCU) for the task.

Interested in learning more about the retro modern Nixie clock? You can check out the project’s official page loaded with additional images here.

Previous Nixie-based projects featured on Bits & Pieces include “The ATtiny1634 Nixie clock,”  “Building an Arduino-powered Enigma machine,” and “Atmel’s ATmega645P goes tick tock.”

Arduino Uno powers this Game of Life clock

The Game of Life (aka Life) can best be described as a cellular automaton created by the British mathematician John Horton Conway in 1970. Essentially, it is a zero-player game, meaning that its very evolution is determined by an initial state, requiring no further input. Simply put, an individual interacts with the Game of Life by creating an initial configuration and observing how it evolves.

The game made its first public appearance in the October 1970 issue of Scientific American, having been featured in Martin Gardner’s “Mathematical Games” column. As Wikipedia notes, the game is rather interesting from a theoretical point of view, as it has the power of a universal Turing machine, namely anything that can be computed algorithmically can be computed within Conway’s Game of Life.

Recently, a Maker by the name of Matthews created a Game of Life style clock. According to HackADay’s James Hobson, Matthews was originally inspired by another Game of Life Clock featured on HackADay a few months ago, although he did implement a number of critical changes.

”First, Matthews wanted a much bigger playing field, so he found a 16×32 RGB LED matrix. Second, he wanted the time to always be visible so it actually works as a functional clock,” Hobson explained.

“At the beginning of every minute starts a new Game of Life which plays over top of the time displayed. Three buttons on the top allow for many adjustments including brightness, timezone, speed, colors and even edge behavior.


The Game of Life clock is powered by an Atmel-based Arduino Uno (ATmega328) paired with a Chronodot RTC module to assist with accurate time keeping.

Interested in learning more about the Game of Life clock? You can check out the project’s official page here.