Tag Archives: ATmega644p

This robotic arm writes the time on a Magna Doodle

Clock a Doodle doo!

Ah, the good ol’ Magna Doodle. For kids, it’s a neat toy. For parents, it’s a chalkboard without the mess. For Makers, well, it’s an innovative canvas to keep track of their day.

The idea to devise a mechanism that can write the time in pen or marker isn’t all that new. Not only isn’t it innovative, it is only a temporary solution as pens run out of ink and markers dry up. Inspired by a dry-erase doodling clock that he built a few years ago as a joke, Ekaggrat Kalsi decided to do something a little different. The Maker had found his previous gadget to be so mesmerizing that he wanted to transform it into a practical, everyday desk accessory.


For this, the mechanism needed to be a bit more reliable, aesthetically pleasing, and of course, accurate. This got him to thinking: Why not use a magnetic drawing board that could perpetually jot down the hours and minutes?

Based on an ATmega644P, the Maker’s new time-writing machine consists of a Magna Doodle display, a robotic arm controlled by a pair of 1:100 geared 15mm stepper motors, and two solenoids with cylindrical magnets on the end of the arm. The motors are handled by a standard StepStick, while the coils are driven by an L293DD Dual H-Bridge. It should also be noted that the project’s kinematics was solved with the help a fellow user on the RepRap forum.


Before arriving at his latest product, Kalsi devised two prototypes. The first one employed a motor on the base and another motor mounted to the arm, which drove the upper arm by a thin cable. The end result wasn’t as precise as he’d like. For the second iteration, the Maker swapped out the cable for a connecting rod, as the cable kept slipping. Still not perfect. And now, there’s this… See it in action below!

Build your own 3D printer from e-waste for under $100

Can you recall the last time you used your PC’s floppy disc drive? Better question, do any of you young Makers out there even know what a floppy disc is? How about that DVD player, or have your resorted entirely to Netflix? In any case, a Maker by the name of “” has transformed electronic waste into an extremely inexpensive 3D printer — all for less than $100. 


In an attempt to make the community more conscious about the “big problems with the e-waste generation,” Mike began by attaining a pair of DVD disc drives and one floppy drive, which are used to supply the stepper motors for the printer. The Maker then took a PC power supply along with other cables and a soldering iron to create the inner workings of the printer.

After downloading Arduino IDE, he used an ATmega644P based RepRap Gen6 to serve as the brains of the makeshift machine; however, he does note that RAMPS (ATmega2560) can also be used to bring the printer to life. The device runs off of free Repetier Host software, while the remaining components were each devised using cheap lasercut materials.


As far as filament goes, the machine uses 1.75mm bio-plastic filament, which is both easier to extrude and more flexible than the typical 3mm standard. Mike also notes that this size filament also require less power to drive the DIY machine than the 3mm. Aside from being eco-friendly, in comparison to ABS, the selected filament melts at lower temperature, attaches easily to the printing bed and has very little retraction.

As they say, one man’s trash is another Maker’s treasure. Interested in creating your own $60 3D printer using e-waste? You can access a step-by-step tutorial of the build along with all the necessary downloads on its official Instructables page here.

Xronos Clock keeps time with the ATmega644p

The Xronos Clock Kit (v2.1) – which recently hit the virtual store shelves at Adafruit – is an open source, hackable and customizable device powered by Atmel’s ATmega644p microcontroller (MCU).

Aside from Atmel’s ATmega644p MCU, key hardware specs include:


256MB microSD card
  • 22Khz 16-bit Mono uncompressed WAV (audio support)
  • 32×16 Red/Green LED matrix (capable of producing 3 colors: red green and orange)
  • 3x 24mm arcade buttons
  • DS1307 based RTC w/ LIR2032 battery
Digital DS18B20 temperature sensor (-55°C to +125°C)
  • RFM12B (915 Mhz or 434 Mhz) only available in V2 as option
  • USB programming w/ optional FTDI adapter/cable (not included)
  • 6-12 VDC (positive tip) Power Supply
  • 1-3 Watt draw (aprox., depends on Color and Brightness)
  • 7.5″ x 4.75″ x 3.75″ (aprox), 1 lb 8 1/4 oz (687g) w/o external Power supply

The talking clock is equipped with an internal backup battery, while all settings are saved to flash memory (EEPROM). Meaning, alarm setting and preferences will be preserved during a power outage. 

Since all audio files are kept on SD card inside, users can change alarm tones, or replace voice prompts with their own.

Additional features include:

  • Dual custom alarms
  • 10 alarm tones, such as melodies or special effects like trains, thunder or police sirens
  • Change display color to green, red or orange
  • 12 or 24 hour mode
  • Celsius or Fahrenheit selection for temperature sensor
  • Ambient light sensor automatically adjusts display brightness
  • Easy access to micro SD card, backup batter and FTDI

The Atmel-powered Xronos Clock Kit (v2.1) is currently available on the official Adafruit store for $215.