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Saturday, November 2, 2013

UV DLP Pico Projector Experiments Part 1

      I briefly mentioned in one of my last posts about ordering and receiving a pico projector to experiment with. I obtained a re-furbished  AAXA P2JR directly from their webite http://www.aaxatech.com/products/p2jr_pico_projector.html  . 

The victim
      It came with the usual accessories, power adapter, micro-VGA to VGA adapter, composite cables, etc... My intent in ordering this is to see if I can adapt it for use in a bottom-up (or top-down) UV DLP 3d printer. I was a little nervous for several reasons. Normally, I don't just purchase new pieces of technology for the sole purpose of ripping them apart, but I figured I needed to break a few eggs to make an omelet.
       I was hoping that this projector would 'just work' and be able to cure resin without any modifications, but I pretty much figured it was going to need some mods. After powering it up, connecting it to my computer, and projecting silly images across my walls, cats, and girlfriend, I decided to get down to business. I ran my latest development code of 'Creation Workshop', sliced up a model, and chose a nice slice to test with.

Initial resin test
      I put a few drops of UV resin in a plastic sandwich bag, laid it flat, and projected an image slice. It went pretty much how I figured. After about 30 seconds, I checked the bag, and to my disappoint (but not surprise) I saw that it had failed to cure the resin in the slightest. 

      Now, I have it on good source that at least one person in the community has been able to modify a pico-projector for UV DLP purposes, so I wasn't ready to give up yet. I began to prep the patient for surgery.
Back cover off


The green and blue cable goes to the DLP unit's LEDs


A flat ribbon cable connects the DLP to the main board

     I was kinda nervous taking this all apart. What if I break it? What if I nick off a resistor? Am I about to lose 169$ bucks? Well, I hit my stride, and decided to make some progress in the name of science. I was able to completely dis-assemble the projector into it's essential components, the case, the speaker, the battery, the main board, and the DLP unit which was attached to a hefty heat sink.

I gently lifted the little bar that held down the ribbon cable to remove the DLP. After freeing the DLP from the main board, I had a better chance to examine the actual DLP projector without fear of tearing the ribbon cable.

Note the blue/green wires, L-bracket and copper heatsink

Initially, I was a little puzzled by the 2 sets of 4 wires. 

A good view of the optic-path

At the bottom/left of the picture, you can see the L-Bracket, each side has a 4-wire lead. Light is being projected in from 2 sides - each at a 90 degree angle from each other. Notice the funny-looking bluish glass (it's important later).

I figured that the L-Bracket contained the LEDs, and that I was probably going to have to replace them with a better UV source. I carefully sliced through the black rubbery epoxy holding the LED L-Bracket to the side of the DLP Unit.

The removed Led bracket 

I examined the LED L-bracket and noted that 1 led was marked R/B and the second was marked G. Without getting TOO much in theory about how DLP projectors work, I wanted to make a few comparisons between Color-wheel types and LED types.

In a Color-wheel type of DLP projector, a light source is projected through a spinning color wheel. The wheel has an encoder mechanism that tells the control electronics which color the light is currently projecting through. The appropriate color mask is displayed on the DLP micro-mirror array.

In a LED-type projector, either 1, 2, or 3 LEDs are used. Since LEDs can quickly turn on/off, the control electronics will turn on a single color, the DLP chip will display the appropriate mask-image for that color, and the process is repeated for all colors.


An image I found that explains the optic path 
The above image is NOT a picture of my DLP device, but serves to show the portions of the optic path. My optic path is a little different, but has very similar elements. 

Light from LEDs shine through collumnating optics. Dichroic mirrors (http://en.wikipedia.org/wiki/Dichroic_filter) reflect a specific frequency of light through a fish-eye lens, reflect on a right angle, then pass through the DLP portion and out the projection lens.

I knew that the dichroic mirrors were going to be a problem. They only allows a very narrow bandwidth of light through. 

I went ahead and took out the dichroic mirror reflectors and replaced it with a single FSM (Front surface mirror). This essentially blocked off 1 light path, which was alright, because I'm only going to use 1 light path for a UV led.

I've got a bit more to say about this and a few more results, but I'm going to save it for part 2.
Stay tuned.
-Steve





10 comments:

  1. Yeah I know the feeling of buying something brand new just to take it apart and possible destroy it. Nerve racking!

    Nice hacking so far.

    Haven't had a chance to touch mine due to needing to tend to other matters.

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  2. I'll be following your progress very attentively since I'll try to do the same.
    Thanks for posting this.
    Ricardo Mendonca

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  3. I wanted to do this hack with a small projector, but there were a lot of uncertainties I wasn't sure about. Now that you have explained and shown the general setup on the inside of this device, I think things are looking up. It would be great if you could post more pics of the projector, how the module with the lens and L bracket is positioned in the projector main case, and close up pics of the L bracket with the leds, where letters can be visible seen on the circuit. Four wires to each led though!? makes me wish I had this project to look at and test!

    I must congratulate you, and thank you for the great work you've done, with DLP 3D printing software, I am one of them that was struggling to find a software with such capabilities. I wish I could design software like this! Great work!!!

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  4. I'm looking forward to part 2!

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  5. Thanks for the kind words everyone. Hopefully, I'll make all the mistakes so you won't have to make them yourself. I actually used the ~150$ I got in donations from CW 12 towards the purchase of the pico-projector. I've already made a bit more progress on the pico-projector displaying images using a UV LED and a UV Laser. I'm trying at this point to columnate the light better through some make-shift optics to boost the brightness. In another future post, I'm going to also go over using UV Laser and Galvos (currently on order from Ebay/China) along with the projection mathematics and Arduino control.

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    Replies
    1. Hello PacManFan
      I am still looking for an Ac power adapter hack for my aaxa Model P1-J because the 80 min battery is so frustrating. Can you help me or send me a link.I can't be the only person that needs this.
      Flipper

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  6. I just got back from the Brookstone outlets with a DLP pico-projector (only $170). Took it apart and removed the RED LED. Turns out the following UV LED from mouser has the same solder footprint and size LZ1-00UA00-U4, looks like the built in glass lens matches too (dimension wise), but we shall see. When I install it and play with it curing resin ill let you know how it works out. I'm very interested to see how your experiments turn out too.

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    Replies
    1. How did things go with the mouser LED? Any success?

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    2. Hi Dan, I am also trying to replace the RED led in a DLP pico-projector with a UV LED (very similar to yours, except that the power is bit lower). After soldering, I can turn on the UV led, but I wasn't able to get any thing out from the projector? Do you have similar problems? Thanks.

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  7. A lot of the time cheap projectors can be found on e-bay as "Faulty", usually the problem is mechanical such as broken power/video connector or stuffed battery.
    Another alternative source is 3M "iphone projector sleeves" as these are now redundant due to not supporting the 5 and 5S.

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