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Thread: Running the XJ-A140 With Missing Diodes

  1. #231
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    Yep, you could do that I suppose.

    I just thought it would be more ideal to gain the colour purity and solid-state nature of the LED's (no moving parts etc).

    The other reason is that you always lose light efficiency when going through filters. Colour wheel motors are quite noisy too (then again, nothing is quite as loud as the Ca$io's fans!).

    There are some very bright white LEDs available now, so it might be worth a try if anyone just wants a usable projector.
    You would still need to find a white LED with a small emitter area for the best possible light efficiency AFAIK.

    It shouldn't be too hard to work out the colour wheel segment sizes using the timing diagrams (o'scope shots) in my previous posts - the projector appears to increase the amount of "Green" segment used when in ECO OFF (high) mode. So, for simplicity, I guess it would be best to create the colour segments based on the ECO OFF timings (for the brightest possible image).

    Also remember that the colour wheel (phosphor wheel) runs at 2x the frame rate, so is probably fixed at 120Hz (60Hz signal input). This is what creates the two main "peaks" on the o'scope shots.

    I've got no idea where you'd get the actual colour segments from other than another DLP projector though?


    btw, Merry Christmas everybody! (depending on time zone and religious inclination of course).
    I'm just off to bed before Satan Claws arrives on the roof (or whatever his name is).

    OzOnE.
    "It's like lasing a stick of Dynamite."...
    http://www.youtube.com/watch?v=0ds0wYpc1eM&fmt=18
    Surely all PL members have seen this movie?

  2. #232
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    As to my color wheel recommendation... (first off, I don't have one of these projectors YET)

    I think going for simple/cheap is best, otherwise... why not put 24x445nm LDs in it... it would produce the best image, hehe.

    Assuming we're starting with a projector modified to disable the LED and LDs and still spin the wheel...
    I think the first step in testing this would be to use the green light path by placing highly reflective paint on the wheel where we believe the segments should be.
    For testing, you should be able to use any decently bright flashlight. After that we can look for a good white LED as a light source. Next step would be to try modifying the wheel with color filters to use the blue path. I wish I had a stockpile of these projectors to test on, but I'll have to rely on someone else to actually test/implement this.

  3. #233
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    think an SST-90 would suffice?..2300 lumens..@ 4.5v...(i have a great link in my older posts of them running down a VAST array of different LEDS...think its around #170's....lists just about every single LED on the market..with both lumens and voltage specs.
    im still very curious if the CBM 370? by phatlights (cant exactly remember)..would work if you were to bypass everythign and just rig it up right there in the light tunnel in front of the DMD...then pulse each color in time with the DMD....if only the price would com down on it it would be a more appealing idea....cause if it dont you gotta 160 dollar chunk o ya butt sitting there and nothing to do with it!.

  4. #234
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    Quote Originally Posted by ekeup View Post
    As to my color wheel recommendation... (first off, I don't have one of these projectors YET)

    I think going for simple/cheap is best, otherwise... why not put 24x445nm LDs in it... it would produce the best image, hehe.

    Assuming we're starting with a projector modified to disable the LED and LDs and still spin the wheel...
    I think the first step in testing this would be to use the green light path by placing highly reflective paint on the wheel where we believe the segments should be.
    For testing, you should be able to use any decently bright flashlight. After that we can look for a good white LED as a light source. Next step would be to try modifying the wheel with color filters to use the blue path. I wish I had a stockpile of these projectors to test on, but I'll have to rely on someone else to actually test/implement this.
    Actually, I think for easy testing, reflective tape might be best... maybe this:
    http://www.amazon.com/gp/product/B000TR6EYA/

  5. #235
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    Firstly, a very Happy New Year to everyone!

    See - the World didn't end after all! (apparently, it's scheduled for demolition in December).


    OK, I haven't progressed much with the LED stuff over Christmas, but I thought I'd do a quick sketch of the colour segments that you'll need if you want to try modifying the colour wheel itself...



    Now I'm not 100% on the angles yet, but the o'scope shots suggest the segments are roughly like this...

    60 degrees BLUE
    140 degrees RED
    160 degrees GREEN

    So I think I've gone a tiny bit too long with the RED segment in my sketch.

    I just confirmed that the colour wheel turns clockwise (when looking at the "front"). This is marked by the orange arrow on the image.

    The thin YELLOW line on the sketch shows where the CIDX signal is generated. This denotes the start of the BLUE segment, the RED, then GREEN segments follow (obviously, lol).
    You can also see the pen mark in the centre of the wheel (where they've roughly marked the Index signal at the factory).

    The timing of the YELLOW line should match up with the FALLING edge of the Yellow signal in the following o'scope shot...
    Remember, the phosphor wheel spins twice for each frame, so it spins at 120Hz (7200RPM) for a 60Hz video input...



    The above angles were calculated from the ECO OFF mode. This should give the maximum area (length) for each segment (and in theory, maximum brightness)...
    In ECO 1 or ECO 2 mode, the projector simply uses a bit less of the GREEN segment (it turns the lasers ON slightly later in the sequence so the 445nM beam "misses" the first part of the Green phosphor).

    It doesn't matter where the projector turns the RED LED on because it's light bypasses the phosphor wheel.
    In practice, I don't think the PJ ever mixes RED with GREEN or BLUE (only one colour is "ON" at a time).

    I've just put my PJ back together, so I'll play around with the LED sequencer next. Should be easy enough.

    OzOnE.
    Last edited by OzOnE; 01-01-2012 at 08:20.
    "It's like lasing a stick of Dynamite."...
    http://www.youtube.com/watch?v=0ds0wYpc1eM&fmt=18
    Surely all PL members have seen this movie?

  6. #236
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    Ozone...what light or led or light sceme do you plan on using?...im still really phyced about the CBM-380..but cant figure out how i could get each individual led to pulse in time with the DMD (is your led sequencer external or internal?) i figured since you said large area LED'S would be ineffective without proper collimation..this would be perfect cause the leds are like tiny tiny tiny..but pump out alot of light! i still got my grab back of lenses that i plan on testing with and that big honking 4000 lumen led .gotta be one in there...just no data (that one can understand easily)..on the amount of collimation or proper focal length we need...so i figured being systematic about it with some small lenses and trial and error is the way to go.. i mean i got like 60 or 70 lenses should prove some interesting results at the very least and might spark off ideas in other folks.

    oh also do you still have the link to the DMD.pdf you posted a few days ago?... something is majorly wrong with Photolex cause everytime i try to accesss archive files..it gives me a 404 error for some reason..

    hope everyone had a great new years!
    Keith.

  7. #237
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    i dont know if i have posted this before but this is a great shootout of different leds showing voltages and currents and whatanot...its really great to see what the power of a LED really is...

  8. #238
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    http://sunshineopto.en.alibaba.com/p...eet_Light.html


    i did find this in my searching for a collimator for the flat leds..but alas it is 2 inches in diameter

    this one is alittle bit smaller 29.x mm

    http://www.alibaba.com/product-gs/22..._SD_B_LED.html

    this one here has an 8.7 degree viewing angle!!!!
    http://www.thecustomsabershop.com/Lu...ngle-P537.aspx

    i found this to be very informative though it has information not pertaining to projections...the info is still very useful!

    http://www.imagineeringezine.com/ttaoc/t-circuits.html

    this is a cut and copy excerpt from its collimator section


    LIGHT COLLIMATOR
    For long range applications, the light emitted by the LED must be bent into a tight light beam to insure that a detectable amount of light will reach the distant light receiver. For most LED applications a simple plastic or glass lens will do. As discussed in the section on light emitters, the placement of the lens in front of the light source has the effect of reducing the exiting light divergence angle. Selecting the right lens for the application is dependent on the type of LED used. As illustrated in figure 7c, the lens's focal length should be picked so it can capture most of the emitted light. LEDs with wide divergence angles will require lenses with short focal lengths and LEDs with narrow divergence angles can use lenses with long focal lengths. Keep in mind that the LED divergence angle is usually defined at the 1/2 power points. Therefore, to capture most of the emitted light, a wider LED divergence angle specification should be used when making calculations.


    Figure 7cClick image for larger version. 

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    The divergence angle of light launched using a lens is:
    (LED div. angle) x (LED dia/ lense dia)

    As an example, a 1.9" lens and a 0.187" LED would reduce the naked LED divergence by a factor of 10. A LED with a naked divergence half-angle of 15 degrees would have an overall divergence angle of 1.5 degrees, if a small 1.9" lens were used. A 6" lens would yield a divergence angle of less than 0.5 degrees that is about the practical limit for most long range systems. Divergence angles less than 0.5 degrees will cause alignment problems. Very narrow light beams will be next to impossible to maintain proper alignment. Building sway and atmospheric distortion will result in forcing the light beam to miss the distant target. It is much better to waste some of the light to insure enough hits the receiver to maintain communications
    TOP



    Click image for larger version. 

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    MULTIPLE LIGHT SOURCES FOR EXTENDED RANGE
    For some very long range communications systems, the light from one LED many not be enough to cover the desired distance. As discussed above, a large lens used in conjunction with a single light source may result in a light beam that is too narrow to be practical. The divergence angle may be so small, that keeping the transmitted light aimed at the distant receiver may become impossible. To launch more light at the distant receiver, multiple light sources will be needed. However, as illustrated in figure 7d, a single lens should not be used with multiple light sources. As shown in the illustration, two light sources placed side by in front of a single lens will launch two spots of light, spaced widely apart. Only one of the spots would hit the distant receiver. This mode may be desirable in very rare situations, but for most long range systems, only one spot of light needs to be launched. Adding more light sources in front and a single lens would not increase the amount of light sent to a light receiver
    Last edited by kobra000; 01-01-2012 at 16:26.

  9. #239
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    Ozone..

    why are thre 3 anodes and 3 cathodes noted for each channel when only 2 wires on the orginal Laser diodes are used? (the pdf for the laser diode says the 3rd wire has no connection,and i assume no function!)

  10. #240
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    Does anyone have a ball park figure on the angle of collimation needed? after reading probably thousands of things on it it started sinking it ..most of the planar leds (yes i know)..have a 180 or less viewing angle...(in other words crap for our purposes)...but i keep seeing ones that have like 13 degree viewing angle and 10 and 9....but we need ours tight dont we?..say between 1 or 8mm? cause the DMD is pretty small.....would it be ok to over shoot?...try not to get shrink the angle of the beam down so super tight ive heard a little fudge room as always needed in any project ie heat expansion,cold contraction,unknown variables that affect the outcome in unknown or unforeseeable ways.),cause im thinking the dichros might add a little collimation to them i dont think so,but hey its possible and if so its most likely an imperceptible amount,but i could be wrong!

    but anyway...is between 1 and 8 degrees the ball park..or do we want that thing exactly at 1 or 2 or 3degrees? with say a focal length of 20mm and less?

    i was able to find this one..50mm so its 2 inches wide (think it could be placed in a lathe and somehow ground down,i highly doubt it could be cut with standard lathing stools) but it has a 2 to 90 viewing angle...i dont this one just strikes me as interesting cause all the rest i have seen have like 135 degree viewing angles.
    Last edited by kobra000; 01-01-2012 at 22:17.

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