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Thread: alsdc-RGB1000 troubleshooting green laser diode

  1. #1
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    Apr 2016
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    Laser Warning alsdc-RGB1000 troubleshooting green laser diode

    The green laser has 6 wires!
    See pics. After testing voltage, I was unable to determine the functionality of each of the black wires in reference to the red wire. I'm looking to try to troubleshoot the main control board or the diode itself red and blue diodes work fine. Also note that the fan for the green diode was dead... when measured with meter it only reads 1.6 volts compared to the expected voltage of 12v. Blue laser is measured 12v for the fan and is getting a pwm like variable voltage with the red wire being always positive. The two red lasers work as expected.

    Having a hard time to figure out the 6 wired on the green diode... if its possible to replace and how to determine if that's necessary. Contacted vendor who could not offer any help. Any advice from the professionals on this forum would be very helpful and appreciated. I have enclosed some photos to show the connection as well as the board. If u may wish to contact me for Info please do so here or at jack.maksymenko@gmail.com

    Thank u guys for keep this forum amazing! And helping out all the lil guys who dont have any local laser legends to assist us. I'm happy to have someone to ask these questions to. Much love!!
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  2. #2
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    I'm guessing the green module is DPSS, have you been told it's a diode rather than DPSS?

  3. #3
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    Quote Originally Posted by NobleGas View Post
    I'm guessing the green module is DPSS, have you been told it's a diode rather than DPSS?
    Thanks for your quick response. I have not been specifically told anything. I figured it was something like this:
    https://www.ebay.com/p/100mw-130mw-5...d=372235166437

    The problem with this is, I assume if you use the complete module with the control board, you can provide 12V and the laser will come on.

    However... in order to draw anything useful, the module in my current projector needs to modulate the signal.

    I see that the control board in the above looks like it also has 6 wires going from the control board to the laser module. They are color coded, which is great. But it doesn't help me match them up with the output of my current control board. Any ideas on that front?

    Thank's in advance.
    PS: This is the original poster. My friend posted the question for me since I didn't have an account yet.

  4. #4
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    If you can read any details off the label on the green module, that would be a great help; also, a decent photograph of the driver board might help someone ID it.

  5. #5
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    Oct 2018
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    Hardly any details on the module, other than the warning label.
    Please see the following pictures of the module and the controller board. I hope this can help someone identify it.

    Thanks!
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  6. #6
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    It's likely a DPSS diode. That means the six wires will be:

    Laser diode current +
    Laser diode current -
    Temperature sensor +
    Temperature sensor -
    TEC current +
    TEC current -

    Unfortunately since they're all black, it's impossible to say which wire is what.

    A DPSS laser's output is very temperature dependent. It works in a special way. First, an 808 nm infrared laser diode is shining into a crystal, which acts like a laser itself and outputs at 1064 nm infrared. Then, the light passes through another crystal with a special second harmonic effect that halves the wavelength of a part of the infrared light to 532 nm. This second crystal's efficiency is very temperature dependent. As such, the driving circuit will not only provide current to the diode (like with the two other colours), but will also have a control circuit that checks the temperature (likely a simple thermistor) and adjusts the current to the TEC, that can cool down or heat up the crystal. It's some kind of feedback loop.

    There are pots on the driver that allow you to play around with the parametes of the feedback circuit. It's possible that something changed in the laser system or control circuit which caused the optimal temperature to shift, or the control circuit no longer be set at the optimal temperature. Since these pots are unlabeled, you need a reference manual to have a chance to fix it.

    But it's more likely the diode is just dead, in which case you'd be better off just grabbing a new green laser module, including driver.

    I see on your picture that the control board is also driving the blue diode and the two red ones. That'll complicate things. You can keep this board for the red and blue, but you'd need a new driver for the green one. You'd also need to get the signal from the main controller to the new green driver circuit. I can't tell what is the main controller (a dmx show card, an ilda input board?). Most of them will provide modulation signals between 0 and 5 V, and most laser drivers are compatible with that, but you'll have to verify that. I'm not sure if a multimeter can be used for changing signals, see if you can send a constant signal (full on)...

    If you get a new green module, make sure to look into the 520 nm ones. They are single diode instead of DPSS and as such are simpler to drive. You could even DIY it with a diode from DTR's laser diode shop and a flexmod or BBE driver.

    Make sure you have the PSU sorted as well. It doesn't look like you have a lot of space left in the casing, so you can't take a bulky module that requires a giant PSU. Maybe you can split 12V off from somewhere else?

  7. #7
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    Oct 2018
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    Brilliant, you are on point, my friend!

    I've identified the main components on the attached picture. The 'input controller' has a small LCD screen, and SD card on the user end. It looks like it receives 5V from the board which has all of the potentiometers on it and send R, G, and B signals to the Laser controller. I checked the black and red wired on each of the separate R, G, and B connectors and it appears they are in fact 5V.

    I tested his hypothesis, by unplugging the RGB inputs to the laser controller board. To my surprise, disconnecting the inputs didn't remove the particular color. Rather it turned it on in full. So when the inputs are disconnected, the blue and the red were on all the time. With the blue input connected, the output went all red, and with the red input connected the output went all blue. Also, the polarity on the red/black wires is reversed. Reading red being negative to black...

    Is it common to enable full output of the laser and 'suppress' it, as it were with negative bias?


    Supplying 12V power is simple enough from the on-board power supply. Next I am going to have a look at ordering a 520nm laser output module as you suggested!

    Thank you!

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  8. #8
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    Quote Originally Posted by JMaksymenko View Post

    I tested his hypothesis, by unplugging the RGB inputs to the laser controller board. To my surprise, disconnecting the inputs didn't remove the particular color. Rather it turned it on in full.
    That's bad news. This is not common practice, but rather something done with cheap lasers. I'm not sure if there are many laser diode drivers out there that are compatible with that kind of input. Maybe you can look online for a circuit that adjusts this...

  9. #9
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    No problem. As long as I am aware of this I think I should be able to think up an inverting circuit.
    Any guess as to what range the PWM frequency may be in?

    I'll update my progress.


    EDIT:

    This looks like it would fit in nicely:
    https://www.ebay.ca/itm/520nm-100mW-...5No:rk:18:pf:0

    Just a though: assuming I can, in fact, make a driver for this. How would I go about physically lining it up? The mounting bracket has oval shaped holes for this, but it seems to me the tools need to get proper alignment would need to be incredibly precise.
    Last edited by JMaksymenko; 11-11-2018 at 14:23.

  10. #10
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    Laser diodes are typically not PW modulated. The input signal is amplified directly to the laser - if the modulation input is 5V (or in your case, 0v), the laser turns on.

    The module you're linking to is TTL, which means it'll only listen to discrete, digital inputs - "on" or "off". When the modulation signal is below a certain voltage, it will turn off.

    Most laser diodes are analog modulated (0-5V variable voltage), so you can set a variable intensity.

    I don't know if your laser controller is analog or TTL. Can you dim the laser via DMX? If so, you really want an analog laser driver. If not, go ahead.


    As for hardware mounting... that's my weakest spot so I'm not going to give advice but alignment is indeed a big issue. Most of these Chinese "glue goop" projectors tend to go out of alignment permanently...

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