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Glowboard Plotter

The Glowboard Plotter plots images using 64 UV LEDs attached in a line moved over a 120cmx60cm glow-in-the-dark sheet by a stepper.

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The Glowboard Plotter was built with a piece of 120cm x 60cm Glow-In-The-Dark sheet, a stepper, 64 UV Leds controlled by a MAX7219 attached to a raspberry pi. The Leds are attached to a wooden bar which moves over the sheet. A little webserver is used to receive images and controls the Leds and the stepper so that images are plotted.

Code can be found on github: https://github.com/Eigenbaukombinat/glowboard (webserver.py)

IMG_2156 from Eigenbaukombinat on Vimeo.

  • 1 × RaspberryPi 3
  • 1 × MAX7219CNG 8x8 Matrix Controller IC Interface and IO ICs / Display Interface
  • 1 × DRV8825 Stepper Driver Evaluation, Demonstration Kits, Boards and Modules / Evaluation Kits, Boards and Modules
  • 1 × NEMA 23 Stepper Motor
  • 1 × Glow In The Dark Sheet

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  • Future improvements

    nilo05/29/2016 at 10:04 0 comments

    The biggest problem is that the glowboard is quite noisy. This is caused by the very simple python program, doing the calculation of the images and controlling of the steppers. So, every time the LEDs are updated, the stepper movement is stopped for a short period of time. You can hear the stuttering sound in the video above.

    To fix this, the movement of the stepper has to be controlled by a separate process, which is capable of realtime processing. The easiest way to do this would be to let an arduino control the movements of the stepper, and give our python program running on the raspberry pi feedback about its position.

    Another issue is that the openrails use steel wheels rolling over an aluminium profile. By using steel shafts with some plastic linear bearings we could further decrease the noise.

    Finally, by placing the stepper motor behind the board and adding some dampening material we hope that we can reach a sound level which not annoying to people hanging around.

    All-in-all, these changes mean that we have to build an all new version 2 of the glowboard. Maybe we can increase the (physical) vertical resolution from 64 to 128, which would mean that we have to decrease the distance of the UV LEDs from the board, so that we then can have an "interlaced" vertical resolution of 256px!

    Stll way to go for a full HD glowboard, but hey. :-)

  • Webinterface for sending images to the glowboard.

    nilo05/25/2016 at 22:27 0 comments

    The Raspberry Pi 3 attached to the Glowboard Plotter runs a minimal webserver written in python, which can be used to send images and set number of passes. HTML/CSS was done by @sesshotv, the youngest hacker currently hanging around in our hackspace.

  • Glowboard now plots grayscale images.

    nilo05/25/2016 at 22:10 0 comments

    By applying multiple passes, every pass containing fewer LEDs (lightest pixels are contained in all passes, darkest pixels only in the first, and so on) the glowboard can now plot grayscale images. We limited the number of passes to 10, which gives very nice results. After a while, the contrast decreases (because brightness of the glow-in-the-dark material decreases exponentially), and the image looks smooth for a few minutes.

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Discussions

Elliot Williams wrote 08/30/2017 at 10:51 point

You could change out stepper motors for DC motors with encoders, and flash the LEDs once the band has moved a given distance.  You can probably cut down a lot on motor noise.

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Richard Aplin wrote 02/22/2017 at 22:26 point

If anyone's interested I did same on large scale with a vector scanning UV laser

https://www.youtube.com/playlist?list=PLEAEC79EF55D409D2

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MrwanBaghdad wrote 06/21/2016 at 02:07 point

Another project removed from my to-do list 

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Federico Ceratto wrote 06/04/2016 at 22:01 point

A rollup board could be a nice alternative - if glowboards can be rolled up.

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Federico Ceratto wrote 06/04/2016 at 22:01 point

A rollup board could be a nice alternative - if glowboards can be rolled up.

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Adam Vadala-Roth wrote 06/03/2016 at 16:28 point

very cool reminds me of one my friend made with TinyG

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Ted Yapo wrote 06/02/2016 at 14:11 point

This is an awesome project!  I noticed years ago that some red LEDs cause phosphorescent materials to decay much faster than normal - I've seen others have noticed the same, but can't find a good reference explaining the cause.  Using red LEDs, you might be able to erase and re-write the board more quickly.

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Brian wrote 06/03/2016 at 22:02 point

You are referring to quenching by anti-Stokes stimulated emission. In this case a UV diode is pumping the phosphorescent molecule to a higher energy state, and the photons emitted as it drops to the ground state are of a longer wavelength (lower energy) than the pump photon (Stokes shift).

With Anti-Stokes, one (or sometimes two, three, or even four) photon(s) at a lower energy (longer wavelength) are absorbed by the active molecule (or ion) and one photon of a shorter wavelength (higher energy) are emitted. So if your phosphor is already in the excited state, it may only take one photon of the proper wavelength to cause it to drop to the ground state. This allows control of the phosphorescence time, rather than waiting for it to decay on it's own. 

Often the wavelength of the photon(s) required for the Anti-Stokes emission are twice the wavelength of the phosphorescent emission. So if your emission band is centered at 520nm, the optimal wavelength would be 1040nm. The absorption band can be quite wide in some cases, and could extend down into the visible red wavelength range. The particular absorption / emission bands and band widths can vary greatly with active molecule or ion, and with host material. It does not work with all active molecules / ions.

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nilo wrote 05/29/2016 at 20:48 point

The emitted UV is not harmful to eyes or something. Most of the light is absorbed by the sheet. They noisy sounds are the bigger problem here. ;)

How long the image is visible, depends on the ambient light in the room. In complete darkness, you can see the image for ca. 15 min. At dim light, you can still notice it after 10 minutes. If all lights switched on, it is hard to see something after 3 minutes.

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Baruch Even wrote 06/03/2016 at 08:43 point

Thanks for the info. 

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Baruch Even wrote 05/29/2016 at 18:16 point

This is really neat!

A few questions if I may:

* Does the glow sheet block enough of the UV for the UV not to bother anyone around/watching the machine?

* How long does the image glow after being exposed?

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Terry Daniels wrote 06/03/2016 at 08:04 point

I don't really know too much about the project, but I'm pretty sure it doesn't produce enough UV to bother anyone at all unless you're look right at it. (I have some 5mm  uv leds, and mine on't really leak any light around the sides) and as far as how long it would glow after being exposed, I may be horribly wrong, but I'd say at least a couple of minutes, considering he's able to draw out a large image without it dimming too much at one end.
I hope this was helpful! :)

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