Electrical Parameters to be used

Discussion in 'The Projects Forum' started by Lana89, Feb 4, 2014.

  1. Lana89

    Thread Starter New Member

    Feb 3, 2014
    3
    0
    Hello,
    I am fairly new to this and was wondering if I am in the right track.

    My goal is to get 15 LED's (BXRA- C -0402) connected in parallel, flashing (On and OFF). My input signal is a square pulse (function generator)

    15 LED Voltage and current (from data sheet)
    Max current = 15 amps. (considered 10 amps)
    Max voltage = 9.5 V

    Transistor Char. (from data sheet)
    I am using a power transistor (MJH6284)
    Vce(Sat) = 2V; test = 1.2V.
    Vbe(sat)= 4V; test = 2.5V (considered)

    can I apply :
    11.5V at the base (square pulse)
    10.7V at the collector
    ~1 ohms load resistance which connects the transistor emitter and the 15 LED's

    in order to satisfy my condition of 10 amps i and 9.5V for 15LED's?
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    Welcome to AAC. Hope you will find this site helpful for all things electrical and electronic.

    You did not say what is supplying power to the LEDs.
     
  3. TANDBERGEREN

    Member

    Jan 20, 2014
    74
    4
    OK, I found them.

    Theese are LEDs with 9V Forward voltage at 1A

    To switch theese You should rather connect the LEDs Kathode to the transistors collector.
    The LEDs Anode to a sensible 1Ohm dropresistor (At least 1W type)
    On top of the resistors your positive line from your power supply.
    And on base of the transistor You ahave intended to use, You could put a resistor of 100Ohm in series with the signal from Your signal generator.
    Emitter of transistor to negative terminal on your power supply.

    But this will work only for about ten of Your LEDs.
    To have them all fonctioning, You should divide the leds in two groups, and have them blink alternatively.
    This is easily done by simply put a resistor from the collector of your existing switching transistor into the base of a small signal NPN-transistor (around 1 kiloOhm would do here too) Connect the emitter to ground, collector via a new 100Ohm resistor, then the collector to base of a similar powertransistor You already are using, and the second group of LEDs similar as described earlier in my answer.

    Now you will have half the power used, with nearly the same effect. All 15 LEDs will blink
     
    Last edited: Feb 4, 2014
    Lana89 likes this.
  4. Lana89

    Thread Starter New Member

    Feb 3, 2014
    3
    0
    @MrChip: at this moment a function generator square pulse.
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    You are not going to get 100mA output from a function generator.
     
  6. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    Use a MOSFET.

    Bob
     
  7. TANDBERGEREN

    Member

    Jan 20, 2014
    74
    4
    Good thing Lana89 is using a transistor buffer then.
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    She will still need an external power source.
     
  9. TANDBERGEREN

    Member

    Jan 20, 2014
    74
    4
    And she have that too.
    Capaqble of delivering 10A, possibly as much as 15A. :D
     
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