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Fader without the power LED?
http://metku.net/hwforum/viewtopic.php?f=50&t=4533
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Author:  BBurger [ 12.04.2005 01:00 ]
Post subject:  Fader without the power LED?

If I'm leaving the always-on power LED out of this circuit (That is, removing the parallel POWER LED & associated R2), where do I route the 5V GND?

Do I run it out of pin 4 on the opto-isolator, or directly off the fader (ACT) LED's line?

I'm guessing it should come from pin 4, but would like confirmation before I start soldering stuff!

Thanks - love the site, and this is the first 'real' electronic circuit I'm attempting, aside from wiring LEDs & resistors up for lighting!

Author:  japala [ 12.04.2005 06:50 ]
Post subject: 

You are correct. Just wire the pin 4 of the optoisolator to the ground and you are set.

Author:  BBurger [ 12.04.2005 20:00 ]
Post subject: 

japala wrote:
You are correct. Just wire the pin 4 of the optoisolator to the ground and you are set.


Excellent, thanks!

The 33mf capacitator (C1) - does the negative end of it really just link directly to the 5V ground, with the positive end coming off pin 6?

Author:  japala [ 12.04.2005 20:49 ]
Post subject: 

I believe that the image shows just that. :)

Author:  BBurger [ 19.04.2005 04:43 ]
Post subject: 

Cool, it works! Finally finished this last night, got it plugged in, and it looks great!

Right now the red superbright LED is just sticking out of the front of my fascia, but I'm currently drilling out a little (.5 inch) acrylic cube and sanding the sides of it to frost it. The LED will go into the back of the cube, and about half the cube will stick out of my front panel. Should provide a nice red glow!

Thanks for the help, and providing the project in the first place!

Author:  japala [ 19.04.2005 08:13 ]
Post subject: 

Good to hear that you got it working :)

Author:  BBurger [ 19.04.2005 21:14 ]
Post subject: 

Thanks, japala!

One interesting thing I've noticed: the LED never *quite* goes out. Even with the compupter at idle, no HDD activity at all, there's a tiny red spark of light inside the LED.

Is this normal for circuits of this type? Is my optoisolator malfunctioning slightly?

I'm pretty sure that the stock HDD LED used to go out completely at idle, but then it wasn't a superbright LED like the new one is so maybe I just couldn't see the little glow.

Author:  japala [ 19.04.2005 21:40 ]
Post subject: 

The "transistor" inside the optoisolator doesn't need that much voltage to conduct. I believe that the tinyest amount that is left to the capacitor even when it is almost empty is still enough to make the led shine just a tiny bit. For the skull's eyes this is only beneficial so hopefully it doesn't matter you that much. There could be ways to empty the capacitor even better... perhaps by connecting the + side of it a ground via a small resistor but this is something that you need to test if you are interested. :)

Author:  BBurger [ 20.04.2005 07:44 ]
Post subject: 

No, it doesn't matter that it's still glowing. I was just curious, and wanted to make sure it didn't mean there was something wrong with my circuit!

Thanks again!

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