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Hacking the Crayola POV Dome Thing

I found a Crayola Digital Light Designer in a bargain bin and thought "What a Hack TREASURE!!!"

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The Light Designer is an interactive persistance of vision drawing dome where you can draw pictures, create animations and play games, but you cant do what ever you like with it so it needs to be hacked.

Here are a few videos of the finished hack

povNano05.zip

My uncommented hacked code for the adventurous, it displays a flapping bird

Zip Archive - 3.62 kB - 01/29/2020 at 21:48

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povSignals.jpg

Signal from the controller board to the Led bar

JPEG Image - 38.06 kB - 01/22/2020 at 02:11

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ledConnections.jpg

Cable to the LED bar

JPEG Image - 56.84 kB - 01/22/2020 at 02:10

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  • What Language Does It Speak?

    darrenLindley01/22/2020 at 02:41 0 comments

    I connected the boards up to 5v but the boards wouldnt work, I theorised there is a synchronising LED and detector that triggers the writing of the LEDs, without the detector picking up a pulsing light the LEDS dont light up.  I got out the Arduino and wrote a program which would pulse an IR LED at a rate I can vary via the serial port and taped this LED to the detector.  It worked, the LED bar flickers and if I moved the bar quickly I could see an image (theres an image of it in the gallery). Once I had the boards running I connected hooked up my logic analyser to the ribbon cable connected to the led board (via a header I solder to the board), fortunatley the positive and ground pijns were labeled.

    I was expecting a similar protocol to the a shift register driven led matrix display I had built previously, so it took me quite awhile to make sense of the protocol.  I was a bit confused for awhile because there didnt seem to be a regular clock, but it turned out the samples of the clock line werent perfectly regular which made it hard to recognise. Once I made out the clock I could see the dataline and two enable lines, it seemed to bean SPI protocol, I wasnt 100% sure so decided to replicate the pulses in code, at least to get it all going then may be implement SPI later. 

    The display runs a start up with a sequence of  leds running up, down and back up the display, this gaves me something to relate the logic data to. Before the sequence starts an initialising data is sent to the display, I dont understand what it does but all I have to do is send the display the same sequence so dont need to understand it (would be nbice to though). 

    Data is sent through the data line, a display enable line enables the display, 2 frame lines are used to address the line of leds, the first frame line enables the first 16 leds and the second frame enables the last 16.  12x8 bits of data are used to display one line of leds, these can be broken up into bitmaps for each colour component of a group of 8 leds. 8bit for red component of first 8, 8bits for green, 8bits for blue, 8bits for red of next 8 leds and so on.  The data is prefixed with 8bits of addressing data 0x80,0x81,0x82,0xC0,0xC1,0xC2, the same is used for the last 8 leds.
     

  • Whats inside?

    darrenLindley01/22/2020 at 02:39 0 comments

    The first problem, the screws had 3 grooves in the head and I had no screw drivers for this, I had to use a small flat head. The base came off first, containing a circuit board with 3 leads connected to some slip rings providing connections to the spinner. Removing the top dome gave me my first look at the spinner, comprising of a frame to hold a top horizontal pcd connecting to two other pcds at each end, one holds 32 RGB Leds and connects via a 8 wire ribbon cable and the other holds 17 light detectors connected via a 18 wire ribbon cable.  The top pcd contains some kind of integrated circuit under a blob of epoxy, there is a labelled USB pinout on the the board, three leads comming from the slip rings, the +5v line is labeled.

    The next task is to remove the spinner so I can use a logic analyser to look at the signals going to the leds. There's no obvoius way of removing the spinner, but I could see 3 screws holding the motor cover on, maybe this may release the spinner.  It didnt, I fiddled for a bit, finally giving it a bit of a rip and pulled it away from the main housing. 

    I had removed the spinner from the housing but to get it back on I need to feed the slip rings through the slip ring wipers, the motor housing still attached to the spinner made this very difficult. When I eventually got the spinner back on, the device didnt work. I removed it again, there must be a way to remove the spinner from the slip rings inorder to reseat the slip rings, fit the motor cover and then connect the spinner. After much banging and pushing I managed to get the spinner off, assemble the device and got it working again. This is hard to imagine unless you have one, the point Im trying to get across is  taking something apart with the aim of putting back together and have it work can be frustrating but one of the main arts of hacking. 

    I disconnected the one of the wires to the motor so I could check which of the other 2 unknown wires was the ground, then proceeded to disconnect the boards from the spinner.  The main pcb is held in place with two screws and both the led and the light detector boards unclip from the spinner. 

  • Initial Look

    darrenLindley01/22/2020 at 02:23 0 comments

    During my usual rummage through the clearance shelfs in a local department store I found a kids toy, The Cryola Digital Light Designer. It looked like some kind of POV (persistance of vision) display,  but was only $15 (AU) and was a kids toy.

    I bought it, took it haome and after finding a power adaptor I got it working. Basically it was a drawing device, it came with an LED wand used to draw to the screen of 32 rotating leds. It had many different activities to choose from ranging from creating drawing and animations to racing games, but it was noisey and limiting.

    Ive always wanted to build a POV display but didnt really have enough reasons for such a project to get to the top of the todo list, such a project required building a balanced spinning harness what could supply power to some circuitry and a good reason to spend the time and effort. Finding this thing gives me the head start I need and for $15, its not a huge investment.

    The main thing I want this to do is to be able to display images Ive created on a computer and up loaded to it, even turn it into a computer display.

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darrenLindley wrote 02/04/2020 at 21:17 point

This project is from 2014, I had published it as an article on one of my Wordpress sites which has since been retired, so for prosperity I rewrote it on Hackaday.io.  The "Dome Thing" was a noisey thing I had lying around till I down scaled to move house, Ive kept the electronics but the POV is no more.  I compiled this write up from my notes, the original article had more detail, I thought I saved the wordpress database for it but couldnt find it in my archives, Ill have another look soon.  Thanks for your interest.

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Dan Maloney wrote 01/22/2020 at 17:17 point

My old "Lite-Brite" from the 60s looks a little dull by comparison.

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Mike Szczys wrote 02/04/2020 at 16:03 point

I think I also missed all the cool toys. Great job @darrenLindley  making this one a lot more awesome with the added Arduino. Are there more details on the process?

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