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Author Topic: Help on Power_LED/HDD LED Mod  (Read 3777 times)

viridius

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Help on Power_LED/HDD LED Mod
« Reply #10 on: March 02, 2004, 07:18:58 PM »

I'm pretty sure the emitter-collector current of a 2N3904 is 600mA.  You can, of course, take it to the next level with FETs.
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rukcus

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Help on Power_LED/HDD LED Mod
« Reply #11 on: March 02, 2004, 10:35:33 PM »

linear: can you draw up a quick diagram of what you're talking about. I'm sitting here scratching my head wondering what hooks up to where. Especially with the opto-isolator, which I do have a few spare.

Also, how could I make this expandable to more than one LED? Would I just have to mirror Macro's http://www.bit-tech.net/article/58/ ?
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linear

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Help on Power_LED/HDD LED Mod
« Reply #12 on: March 03, 2004, 12:47:36 PM »

Quote from: viridius
I'm pretty sure the emitter-collector current of a 2N3904 is 600mA.  You can, of course, take it to the next level with FETs.

200mA, but that's still gonna drive a stack of LEDs.


Quote from: rukcus
linear: can you draw up a quick diagram of what you're talking about. I'm sitting here scratching my head wondering what hooks up to where. Especially with the opto-isolator, which I do have a few spare.

Also, how could I make this expandable to more than one LED? Would I just have to mirror Macro's http://www.bit-tech.net/article/58/ ?


I can draw one, but I can't scan it, sorry. So you'll have to make do with some 1337 ASCII art:
Code: [Select]
                       /----|<|--|<|--|<|--/\/\/--o +12V
                      |/
          +---/\/\/---| NPN
          |           |\
          |             \--------------------------o gnd
HDD o-----+
          |             /----|<|--|<|--|<|--/\/\/--o +12V
          |           |/
          +---/\/\/---| PNP
                      |\
                        \--------------------------o gnd


Those strings of 3 LEDs + a resistor, they each draw 20 mA (less if you want, just use a bigger resistor).  Combine as many of those strings as you like in the collector circuit, up to the 200 mA rating of the transistor.

I don't care much for FETs, I'd rather go to a complementary pair of BJTs that can handle more currnet, like TIP31A/32A. 3A collector current to play with, about 69 cents.  :thumbsup:
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viridius

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Help on Power_LED/HDD LED Mod
« Reply #13 on: March 03, 2004, 05:56:50 PM »

Quote from: linear

200mA, but that's still gonna drive a stack of LEDs.

My mistake.
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