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Making PlotClock



Building the PlotClock by Joo from ThingiVerse 
with English Character support


  • Plotters are fun things. One can move in a 2D space and do very interesting things. Been fascinated by plotters from a long time. Notable mentions like the Drawbot, AxiDraw, EggBot, etc.
  • Always wanted to build a small inexpensive one which did not require too many components or a lot of domain knowledge.
  • One of my favourite past-times is to ThingSurf ie check which open source designs are available and try to make them, either on Thingiverse or Printables, etc. Its a lot of fun and because these provide designs for real-world things,  one can study and learn from them and also extend them to do other things.
  • There is also a requirement of a device that will be a low-power notice board, like a limited power device that will just consume power for a short time, do some useful work, maybe display a message and go back to sleep. Things written on a sheet of paper remain visible for a long time. So it would be nice to have a device that can write. And as a plotter can do this it is a suitable thing.
  • Also, I do not remember the day of the week as most days go off in a blur. So a device that does time and day/date is much needed.
  • So on one of these ThingSurfs, I found this clock: PlotClock by Joo
  • It is an amazing design that uses just three off-the-shelf SG90 servos and also provides a mechanical base for housing the motors. 2 motors for moving in a XY plane and 1 for the pen up and down. The code is also open source.


  • The above picture shows what PlotClock sample output looks like.
  • The PlotClock software sets the time and writes the 24 hour time on the board.
  • It only has support for numbers and there is code to write the numbers, erase the board using a Dry erase marker with a sweeper that has an eraser base.



  • The 3D files were printed on a Creality Ender printer by a 3D Printing service provider and above is the intermediate assembly stage.
  • Some of the issues were how to connect the servo motors to arms. The holes on the arms and frame had to be enlarged to fit the M3 screws. And earlier I had used 10 mm screws but the screws used to keep falling off so reversed the bots and nuts and used 20mm ones. The servo horns were glued to the base of the arms and to the lift servo, standard servo screw was connected to the horn.
  • The calibration program has to be run so that the servo arms move in an expected pattern.
  • Above is another intermediate phase with the arms
  • Everything has to be just right, the arms have to horizontal, the pen up and down mechanism has to be straight, the sweeper position has to be known. A little variation/play can cause it to go off and not write anything.
  • After playing around with the sample program, I decided to extend this to study the mechanism better. Basically added a CLI interface to manipulate various things with commands: arm lift up and down, pen move to xy coordinates, sweeper activation, speeds of movement etc. If anybody is in need of this maybe can upload it. It helps study and refine the mechanism better.
  • Also after getting the basic version working predictably, there was a need to add English characters.
  • So studied the way the Clock writes it and added the Alphabet.
  • Changed the program to support ASCII character set (though not implemented all) so that strings can be printed.
  • Also added support for an RTC with a DS3231 (it has higher accuracy than a DS1307). One can set time and the clock also reads this and starts writing the time and on a another screen the day and date.
  • There are many other cool uses of this mechanism which will be tried later.
  • A splash image too was added for some Chamak(Bling). It reads time from the RTC, writes hour and minute, erases it , writes the Month, Date and Day endlessly.
  • It is indeed a fun thing to build. Below is the video played at 2x speed.





 



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