Hard drive activity led array

T

TKEcowboy

n00b
Joined
Aug 29, 2005
Messages
24
I would like to build a 6 led array to show hard drive activity. I don't want this to act like a meter, just something simple, either all on or all off. I have mounted six 3 volt LEDs on a pcb, but have no idea how to wire them up. Everything I've tried has failed. At first, I thought all I had to do was run the red wire to the + pin and the black wire to the - pin on the first LED, then connect them down the line keeping + wired to + and - wired to -, but when I do this, only the last LED in the series actually lights up. What am I doing wrong?
Also, keep in mind that while I have worked as a computer programmer for 15 years, I am still very new to building electronics. I cannot currently read schematics, but I'm trying to learn.
Thanks.

Glenn
 
From what you described, it's a bit hard to visualize what you did. Is it something like this?
Code: 
Red wire
|
|
+-->|--+
+-->|--+
+-->|--+
+-->|--+
+-->|--+
+-->|--+
       |
       |
  Black wire
Where the -->|-- are diodes? If so, you'll need to put a current-limiting resistor in line with each LED.
 
Yeah, sounds like he put them in serial instead of parallel. I think if he powers it off the mobo header he doesnt need the resistor but everyone always recomends the use of the resistor so its probably best.

If you want to put so many in you can always consider the nightrider mod :D
 
I would strongly recommend that you not use the MB header directly. Get an opto-isolator and use it to drive the leds, and the header to drive the input of the isolator. And, yes, if you don't put a resistor on each led, they all will not light, as they have to get to a certain voltage before they do light, and that voltage varies on each led (not much, but enough to make a difference), so whichever one has the lowest voltage lights. The resistors will help with that.
 
120ma/typ (20ma/typ x 6)


Thas alot of jooce.


Picturing this but it may need some tweaking. Assemble at own risk.

NPN BJT

HDD ACT. -> 10k Res -> BASE

5v -> COLLECTOR

EMMITER -> 50 to 30 Ohm 1/2watt Res.(or individual 150Ohm 1/8th Watt with each LED) -> LED ARRAY
 
Will that work? I'm pretty sure that HD indicators are negative trigger. The + pin on the MB is just a current limited +5V. The activity is done from the - terminal. What you said would just leave the leds on all the time...
 
To me it sounds like he has them wired up in parallel, but only 1 is in the correct polarity. Id say good thing as it probably wouldn't be able to do all 6 as said before.

This shows how to use an optoisolator for this means(uses schematics though). Unfortunately the 4n27 optoisolator can only source up to 50ma, which is enough to power only about 2 leds.

If this is all confusing you... The optoisolator is basically an led that shines at a transistor that is sensitive to light. The transistor then powers whatever is needed. It isolates because the led and transistor are not actually connected electrically to each other. The only thing transmitted is light. This is all inside the little chip so you can't actually see the tiny led it uses.

Ill try to come up with a simple solution to the power issue of the 4n27. Its 2:30am and brain is not funtioning well.

It sounds like this person is rather new to electronics so Id imagine anything else besides pictures(not shematics) will only serve to confuse. I don't mean to harsh you guys about it, but I don't think its realy gona help the guy out at this point. It seems like he has already been intimidated enough to not reply. I just hope they may still be watching the thread.
 
yep, I'm still watching :) I just haven't gotten back to the project for a while. I am pretty new to electronics. I do a lot of basic stuff, but schematics are over my head right now. I'm working hard to learn, though. Thanks for the input. Luckily, one of the other programmers at work spent a few years as an elctronics repairman, so I'm getting so good feedback from him. At least for what little he can remember :) Thanks again.

Glenn
 
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