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Serious problems with a large number of DLP Pico Projectors (Development Kit version 2)

Jing Liu1
Prodigy 10 points

We are prototyping a projector array with a large number of Pico projectors (around 70 v2.0 development projectors kit).  While each projector comes with its own individual power supply, it would be prefer to have a common shared power supply that is more efficient and takes up less space.  With this goal, we built a new power supply that can output 5v, 240A and can drive multiple projectors in parallel.  Each plug on the power circuit outputs 5v measured by multimeter, which matches that of the standard individual projector power supply.  We have successfully driven 18 projectors using our own power circuit for several weeks.  Unfortunately when we tried to add additional projectors with the same design, projectors started to fail.  In some cases, once we plugged in the plugs with our power circuit, the projectors start getting hot even we don't press the power switch button on the projector.  In other cases there was even smoke coming from inside the projector.  Obviously this is bad.
 
  Here are the symptoms of the broken projectors:
 
  1. the indicator shows red instead of green when turned on, no light coming from the projector lens
  2. the indicator shows green normally but no light coming from the projector lens
  3. the indicator turns green as soon as the power adapter is plugged in, even without pressing the power switch button. no light coming from the lens though. indicator cannot be turned off.
  4. the indicator never turns on, no light from lens either.
 
Basically we would like to know what the indicator light means in different cases, as this is not covered in the online documentation / forums.  We also could not get through to TI technical support on the phone.  Our suspicion is that the power output might be fluctuating a little bit which causes the power chip of the projectors to fail.  Is this possible?  Alternatively maybe the change in the load in the circuit with additional projectors caused the failure.  We are currently trying to debug the different symptoms of the broken projectors in hopes of fixing at least some of them.  We have more than 30 malfunctioning projectors.  If anyone has seen similar behavior or has deeper knowledge of the TI circuitry we would appreciate any help.  Thank you very much.

  • 0
    TI__Genius 9935 points

    Jing Liu1,

    Welcome to the DLP & MEMS E2E forum.

    I am very sorry to hear about the issues that you have encountered with your DLP Pico Kit v2 units. Let's start with the power supply. The DLP Pico Kit v2 requires 5V @ 2A. If you have a power supply capable of 240A, but with good 5V regulation, then you should have no problem driving up to around 120 DLP Pico Kit v2 units at the same time. Of course, this will require adequate (large) gauge wire to prevent excessive voltage drop over the length of the run. This could be a problem at such a large current - so check it out with a "dummy" load which will pull only a few amps, but will allow you to determine the resistivity of the supply line, and therefore calculate the voltage drop under any load.

    The important thing is that the 5V regulation plus voltage drop hold the voltage at any tap point to 5V +/- 10%. This is absolutely necessary - at every tap point. It is also necessary that under any and all load conditions the voltage does not exceed 5.5V, even for a momentary spike. This is highly likely to damage or destroy the DLP Pico Kit v2.

    As for the LED indicator - the normal operation is that the LED glows green when the DLP Pico Kit v2 is powered up by touching the momentary contact ON button (next to the LED). It will turn red if there is an initialization failure, or other error condition which occurs. If the LED turns red, remove power from the kit and verify that the supply voltage is correct. If the supply voltage is correct, reconnect the kit to the power supply. Before the ON button is pressed, the Pico Kit v2 should not show any light from the LED, until the ON button is pressed. It then may flash red momentarily, then turn green, and remain green after the LEDs of the projection system come on. You should see the inital splash screen projected, then after a few seconds, the screen will go black if you do not have an HDMI video input, of an internal operation selected via i2c command.

    The Pico Kit v2 units which are getting hot before being turned on, or are showing a red or green LED before being turned on, are not operating correctly. They may be damaged - perhaps from an over-voltage spike. The ones which are showing a green LED, but nothing is being projected, please cycle these off and on again and check whether you see the splash screen. If not, then they are also probably damaged.

    We do not offer repair for damaged Pico Kit v2 units. You may attempt repair yourself, if you have the facilities and capability. If you do not believe that you damaged any units with over-voltage, you may contact the vendor from whom you bought your Pico Kit v2 units to inquire about any warranty or return that they may offer.

    Again, sorry for the problems you are experiencing. If the units are not subjected to over-voltage supply, or otherwise damaged, they should operate fine. We have found them to be very robust in operation.

    Best regards,

    Pascal

  • 0 in reply to Pascal DLP
    Prodigy 20 points

    Hello Pascal DLP,

    I am working on the same Pico projectors work as Jing Liu1. I have a question about Pico. We are now hooking up about 70 projectors to build a Pico array and finding a way to turn on and off them easily (hopefully at once). It would be a little bit pain to turn on Pico one by one for 70 times. I am wondering if Pico has any hardware function with which we turn it on without touching a button. If it has such a hardware capability, it would be really helpful for us to control the switch of a large number of projectors at a time (e.g. connect all power wires to one and just connect it/ create a circuit board to manipulate them etc). I searched for a specs document, but could not find one. If you know anything about this and/or have suggestions, please let me know.

    Thank you very much in advance.

  • 0 in reply to Koki Nagano
    TI__Genius 9935 points

    Koki,

    Welcome to the DLP & MEMS E2E forum.

    Yes. There is a way to control the Pico Kit v2 power through a pin PWRONZ on the Auxiliary port. Please refer to the Pico Kit v2 Users Guide (http://www.ti.com/lit/ug/dlpu003a/dlpu003a.pdf) Figure 2-4. Auxiliary Connector on page 10. The PWRONZ can be pulled low momentarily by push-button, relay, or open-drain FET to activate/deactivate the Pico Kit v2 power. You may also get the schematics for the Pico Kit v2 from DigiKey (http://digikey.com/pico). Look for PWRONZ on the mainboard schematic.

  • 0 in reply to Pascal DLP
    Prodigy 20 points

    Thank you for the quick reply.
    Actually we designed a circuit board to test if we can use it for turning on/off Picos, but we found that if the number of Picos are large, our system went unstable. So I am wondering if there is a way to turn on the Pico automatically as soon as power cord is plugged in, instead of using an extra circuit board (e.g. modifying register etc)?

    Thank you.

  • 0 in reply to Koki Nagano
    TI__Genius 9935 points

    Koki,

    There is no register-based auto power-on function in the Pico Kit v2. The PWRONZ method is the recommended way to implement this feature. I don't know how you have implemented this, but I would guess that the observed instability in your multi-device system is probably due to trying to use a single pull-down for too many units on a long aggregate of wiring. Also, even though the pull-down on each unit does not involve much current, the sum of many devices could add up to several mA. Driving long stretches of wiring without introducing noise problems is a challenge, but careful layout and design can tame these beasts.

    Could you share the method of driving these units? The distance between units? The wiring method (shielded, twisted pair)? Maybe I can see something and make a further suggestion.