Controlling LED Piranha with PWM controllers

Discussion in 'The Projects Forum' started by aquarius, Oct 26, 2009.

  1. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    In my project I need to control intensity of 8 LED Piranha by using following components(see an attached file):
    - LED RGB Controller ( simply changes combination of R,G,B colors)
    - OPTO22 ODC15 Solid state relays module
    - 8 independent PWM controllers (work from software and change output voltage from 0 to 12VDC)
    - 8 LED RGB Piranha 12VDC, 25mA, with resistors
    My point is to make dimmable 8 LED Piranha while the LED Controller changes colors. Each LED performs according to the PWM Controller output voltage.
    I've already made and tested only one LED. Works perfect.
    Don't know where to connect other 7 negative outputs from PWM's.
    Do I have to have 7 more OPTO22 or there is another solution?
    Need help.
    Thank you.
     
  2. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Since the negative outputs of the PWM provide the path from the current to return back to its source, they can probably all be connected together. It looks like you have already connected together the negative side of the the RED, GREEN, and BLUE loads at the OPTO22.
     
  3. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    I've connected only one and it works. If to connect all negative outputs from PWM, the output voltage from 0 to 12VDC doesn't change. The same time all controllers get input signal from 0 to 10V.
     
  4. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Can you list all of the part numbers, and attach data sheets if you can, of all of the components of the system? The LED controller, PWM controller, module with OPTO 22 parts in it, etc...

    I must not be understanding the diagram correctly.
     
  5. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    See an attached specs for OPTO22 ODC15 and PWM controller.
    The LED Controller had been taken from broken LED bulb. No indications on it. It's simple sequencer, which has 12VAC input and R,G,B,Vcc outputs.
     
  6. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Just to see if I am starting to understand the setup a little...

    Are you using Common Anode LEDs? Is the PWM+ signal going to the Common of the LEDs always at +12VDC? The actual PWM signal at the set frequency is coming from the PWM- and is pulling the LEDs on through the OPTO22 device?
     
  7. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    I think since you are using a unique PWM signal to be routed through the OPTO device, the current setup would require 7 more OPTO devices.

    However, I think if you use common cathode LEDs you could drive the common pin with the PWM- signal, which is unique for each controller, and route the 12VDC into the OPTO device. Each of the LEDs requires the 12VDC to light so you would only need one OPTO device. Piranha LEDs come in both varieties.
     
  8. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    The Piranha has Common Cathode(+). See the initial diagram. In that case only one PWM works properly with one Piranha.
    More info about PWMs. All PWMs use mutual (-) for the input signal.
    Could you clarify your idea of using only one OPTO22 for all 8 PWMs.
     
  9. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    This is what I was thinking...
     
  10. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    Sorry, looks like I already use your proposed diagram. Look at my diagram. Everything works fine only for one PWM connected.
     
  11. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    What is the voltage on the COM pin of the LED? 12V or PWM signal?
     
  12. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    COM pin of the LED uses +12VDC from PVM
     
  13. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    That is why I think your setup is closer to the first picture...
     
  14. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    I clarify again. The PWM outputs is used to power and fade LED. The negative is connected to the OPTO22. The positive is connected to the COM of LED.
    I've noticed other thing in this circuit, if I connect only one negative output from PWM ( other 7 are not connected) to the OPTO and all 8 positive PWM outputs are connected to the 8 COM of LEDs than all LEDs are powered and change color according to LED controller and brightness according to the PWM. But I don't need this effect.
    I've checked everything with two separate OPTO22 (I have only two modules OPTO22) for two LEDs and everything works like I need. But 8 OPTO22 take space and it's costly. Hope you understand my point.
     
  15. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    I understand your point. I still think your configuration is closer to the first picture.

    I think the positive of the PWM, which you connect to the COM of the LED, might be a constant 12VDC. The negative PWM signal is the fluctuating portion which is controlling the output of the LED or LEDs.
     
  16. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    What is your suggestion? I've mixed up with all connections.
     
  17. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    There is a picture in post #9.

    The 12Vdc above the OPTO22 would be the 12Vdc supplied to the PWM boards. The FET at the bottom would be the PWM- which goes into the COMMON(-) of the LEDs. You will need to get different LEDs, the Piranha LEDs come in both varieties COMMON(+) and COMMON(-).
     
  18. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    As far as I understand, first of all I need to get LED Pirahna with Common Anode(-) and then rebuild all circuit according to your proposed diagram. Correct?
     
  19. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    You can start building it by using only one color of each tri-color LED and make sure the concept works. That way you can see if you can get independent control of eight LEDs with the eight PWMs before you invest in the new LEDs.

    In the end, you will need to buy the new LEDs.
     
  20. aquarius

    Thread Starter Active Member

    Mar 14, 2009
    33
    0
    You said: "You can start building it by using only one color of each tri-color LED and make sure the concept works." Means start working with existing RGB Piranha witn COM Cathode?
     
Loading...