Hey Bill.....A Quest abt 555...s

Discussion in 'General Electronics Chat' started by R!f@@, Jan 12, 2011.

  1. R!f@@

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    Hi there Mr. Timer.

    I was wondering what you would recommend to PWM a 20W Led.
    Specs are 12V at around 1.7A.

    Need something as simple as possible, to make the circuit small. Like to drive a logic level HEXFET used in mobo's...I will use a high current one to make the circuit as feasible as possible.

    Brilliance control need to be 20% to 100%. Power supply will be 12V.

    I know I shud have gone thru the database. I need to make this quick. No time for trial runs. So I hope you wud take some time to just post a schema that I could make in one go.
     
  2. R!f@@

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    Ouch..
    U just beat Bill by a pic..
     
  3. retched

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  4. R!f@@

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    It is not as simple I thought ..it uses another chip isn't it.

    Retched...u must be mistaken...it does not use a FET.

    But this is handy to make backlit. Is this thing possible to add any no. of LED's
     
  5. retched

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    I was trying to delete it before you read it.

    You can use a 10f204 for the job.

    You would need to add a MOSFET, and a POT to adjust PWM duty-cycle for dimming.
     
  6. Wendy

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  7. R!f@@

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    [​IMG]

    Hey Bill...
    I Stole ur schematic idea to make my PWM.
    Made the circuit and blew a 1W 3.7V LED, was in such a hurry that I never realize that I had 12V applied. The Led Flashed a couple of times and died. I too was blinded for a while :p.

    Finally realized the hiccup, I do not need to flash the led, just dim it. So replaced the C1 cap with a 0.22uf and Viola.
    I can get from real dim to max or DC or something.
    Measured the frequency to make sure it was pulsing.

    I omitted every component from the output. Instead used a 100Ω R with a logic FET. It drives a 20W led at 12V perfectly @ 555 Hz :D.....(555 Hmmmmm!!!)

    Thanks for the info. Below is a pic for fun

    Have a good day.

    [​IMG]

    P.S...the 555Hz part was just a coincidence.......really....what's with you and 555..HUH!!
     
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  8. R!f@@

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    RM, can u please find me these components...I want to make one...real big one. pls reply
     
  9. Wendy

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    Your LED, is it a 1W model?
     
  10. R!f@@

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    The test was with a 1W. Actual load LED is 12V, 20W one.
     
  11. HallMark

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    Apr 3, 2011
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    Is it working properly now?
     
  12. R!f@@

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    U betcha!!!!!. It's in a friends kitchen cabinet or something. :D
     
  13. Wendy

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    How much current? A 12V 20W LED (which, BTW, doesn't really exist, this LED has a dropping resistor or circuitry) would use about 1.7A.

    Even high power LEDs use the standard dropping voltages, if they are components and not circuits.
     
  14. R!f@@

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    Sorry my mistake it is 20W and I am using 12V adapter which he has on hand .
     
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