2n3055 for PWM driver for RGB leds

Discussion in 'Embedded Systems and Microcontrollers' started by Hedalen, Oct 15, 2011.

  1. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    hi, i am new here and like to ask you something about the 2N3055

    de datasheet tells me:
    ABSOLUTE MAXIMUM RATINGS
    Symbol Parameter Value Unit
    NPN 2N3055
    PNP MJ2955
    VCBO Collector-Base Voltage (IE = 0) 100 V
    VCER Collector-Emitter Voltage (RBE £ 100W) 70 V
    VCEO Collector-Emitter Voltage (IB = 0) 60 V
    VEBO Emitter-Base Voltage (IC = 0) 7 V
    IC Collector Current 15 A
    IB Base Current 7 A
    Ptot Total Dissipation at Tc £ 25 oC 115 W
    Tstg Storage Temperature -65 to 200 oC
    Tj Max. Operating Junction Temperature 200 oC
    For PNP types voltage and current values are negative.


    but can i use it with 5V level and steering the basis with 5 volt from a pic chip
     
    Last edited by a moderator: Nov 1, 2011
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    A 2N3055 is a current controlled transistor.
    For full saturation you will need a base current of about 0.1 X collector current.
    As the pic can only supply about 25 mA , you will not have more than 250 mA at saturation.

    What do you want to control with your pic?

    Bertus
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Of course, you could add a smaller transistor between the pic and the 2N3055 to provide more base drive, but perhaps a logic-level MOSFET would be neater than using two bipolars like that - and it would drain less current from your supply.
     
  4. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    hi, thanks for your quick reactions.
    I have a project here @ home, for making many many leds in the floor
    so that we can see by a power break where we can walk.
    i am talking about nearly a 120 leds ( blue ) and about a 45 rgb leds
    from the rgb leds will change the colors but everytime the red, green or the blue color will light on the same time, so that will be 3 ports on the chip
    the blue leds are sometimes ( max 3 )parallel, sometimes just 1.

    so all power will come out a accu (12V) when the power goes down
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hello Hedalen,
    If you are using a 12v supply (12v lead-acid battery, maybe?) you might use up to three of the blue LEDs in series with a current limiting resistor. If each blue LED needs 20mA current, then 120 LEDs / 3 * 20mA = 800mA total current required.

    The RGB LEDs cannot be operated in series, so you will need a current limiting resistor for each R, G, B leg for each display. The resistor for red LED will be a different value than for the green or the blue.

    Like Adjuster said, you should consider using logic-level MOSFETs.
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    If you want to make many colors, you could use PWM to have different intensities for the leds.
    This thread will give you info on PWM with a microcontroller:
    Creating PWM Using Microcontrollers

    Bertus
     
  7. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    sorry, but the leds are (max 3) parallel
    they have them own 1K resistor and the RGB's are common anode (+)
    and so each RGB has 3 resistors.
    @ one place in the house comes all the cables ( UTP cat6) together, for mounting on a print with the transistors and the chip(s)
     
  8. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    thanks for the link Bertus, i will try to translate it to PROTON IDE
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
  10. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    ones i wil try to work with pic chips and PWM special for RGB-leds, but i think that is difficult for me, be course it is a new world for me
    The big problem will be the time, when 1 color = 0 , 1 = 50 and 1 = 100 percent
     
    Last edited: Oct 18, 2011
  11. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    Hi Bill it is very interesting your link, but i was looking specially for rgb leds with a pic chip
     
  12. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
  13. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    i keeps the problem
    to change from the first color at ≈ 83% to start the next color and at least the third color when the first color is at ≈ 166%
     
  14. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    What is the circuit you are using?
    Can you post the circuit diagram?

     
  15. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    this is what i try to do
     
  16. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
  17. nickelflipper

    Active Member

    Jun 2, 2010
    280
    35
  18. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    @ Bertus,

    at this moment is it not a problem that i will loose 2x 0,7V, because i use 1k resistors so i can use a external power supply up to ≈20V.

    @ nickelflipper,

    i will try to find out what i can use for proton IDE
     
  19. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    If you go to my link on Chapter 10, Transistor Drivers, you will find MOSFETs are much more suited to this application. That particular chapter will describe in detail how to go about it. PICs are a subset of the much larger field of electronics.
     
  20. Hedalen

    Thread Starter Member

    Dec 5, 2010
    19
    0
    okay, listen

    i live in Norway, and it is very expensive to buy here components( 1,50 euro for 1 resistance)
    and i have to drive about a 90 km 1 way.

    is there a possibility to do something with just some pic chips, some bc547b and some 2n3055???
     
Loading...