Complete newbie needs help w/ MOSFET design.

Discussion in 'The Projects Forum' started by jeffkrol, Dec 8, 2015.

  1. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    I have this constant voltage aquarium light that I found can be divided into 3 channels relatively easy.
    Also know that the TC-420 controller will PWM dim LED strip lights. I'm trying to bring the 2 together.
    Problem is the MOSFET output of the TC-420 is on the neg side. The light has a negative bus and each channel is on the pos. side..
    So I thought the below could basically reverse this condition using a p channel MOSFET as a second pulse width switch.
    Important parameters:
    15V constant voltage power supply
    TC-420 is said to work between 12-24V but I believe some have run it w/ lower input voltage.
    TC-430 will not have a "load" to control really..It will just be a PWM output generator..
    Current will be in the new MOSFETS.
    Anyways the point is to change the neg pulses to positive pulses
    Now this may be COMPLETELY wrong but I'd appreciate any feedback on this, EVEN if to say I'm an idiot.. ;)
    Anyways a diagram:

    [​IMG]
     
  2. Bordodynov

    Active Member

    May 20, 2015
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    I believe that you will not come out. If you persist, you will destroy the LEDs. The device is self-sufficient and is not intended to control the transistors. This device utilizes PWM to control the internal transistors. Dimming is an added bonus comes at a lower frequency.
     
  3. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    Hmmm thanks for the response.. but the tc-420 can control 4A 15V of LED's at it output.. Controlling the gate of a MOSFET should be no problem.. In a sense all I am doing is putting a high speed switch onto another high speed switch..
    I have more worries about destroying the added MOSFET's and/or the TC-420 more than the LED's.
    Parts are in only a few details need to be worked out..
     
  4. Bordodynov

    Active Member

    May 20, 2015
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    The LEDs are powered current, rather than voltage. tc-420 is a current source. Without load tc-420 will provide 15 volts. If you Including series with the P-channel transistor LEDs without current limiting device that will destroy them.
    Explain to me the following question. When you write "LED" you mean only LED without driver?
     
    Last edited: Dec 10, 2015
  5. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    [​IMG]

    option 2
     
  6. Bordodynov

    Active Member

    May 20, 2015
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    I was wrong. I apologize. Here I found the cheapest, transistor suitable for you FQP7P06 (MOSFET P-CH 60V 7A TO-220). Digi Key $0.8.
     
  7. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    The 'LED" is really a series/parallel string w/ current limiting resistor..
    4 in series, 1 resistor ..... 3 rows of 4 in parallel .
    As such it runs in constant voltage mode...15V - resistor drop (current limiting) = 4 x V(f) of the diodes.. basically..
    This is the one I was planning on using:
    http://www.nteinc.com/specs/2300to2399/pdf/nte2373.pdf
     
  8. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    Proof of concept.. needs cleanup and analysis:
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
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    I wouldn't use NTE parts; way overpriced.
     
  10. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    Only available
     
  11. jeffkrol

    Thread Starter New Member

    Dec 8, 2015
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    Working...
     
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