Simple question really.

In the project I am currently working on, I need two HDD activity LED's (I am a sucker for symmetry). I know it can be done, but I wish not to blow the HDD header on my new mobo (which I am still a year away from ordering!).

Anyone have thoughts on the safest way to do this?

I know it can be done as Coel had two HDD activity lights for eyes on the Gargoyle case.

Contact twisted he has something like that.

i have an idea

find two led's that have 1/2 half the draw ( in amps) as the one you have now.

Basically you would want a small simple circuit that would draw power from a 5v+ line and you would use a small transistor as your activation... (probably made no since but I can see it in my mind *what there is left of it*).... I will make a diagram unless someone beats me to it... brb

I believe what you would want is something like this..

I am sure that will get the proper effectyou are looking for... but if anyone else would like to chime in please do...

I didnt show a value for the resistor as you would need to adjust it according to the LED's you are using...

Attached Thumbnails

 

hmm... Actually I dont think you would need to use the ground from the HDD header.... now that I think about it.. just the positive to get the signal....

Twisted, thanks for putting that together........ looks a bit complicated.

Here is what I am thinking, we all know that case led's hook up directly to the motherboard and never seem to use a resistor. I have always believed that the mobo header puts out about 2 volts.

We also know you can undervolt a LED with no difficulty (ex. run a 3.5 volt led on 2 volts) it will just be dimmer than the rated mcd.

So, could I not get two 2 volt 20 mA red LED's and run them in series. They would behave as a single 4 volt 20 mA LED, and just run a bit dim relative to their rated mcd.

Any thoughts? Am I missing something?

To clarify, I want to be able to hook 2 LED's up to the HDD activity header on the mobo and have them pulse in concert. I just need 2 for the sake of aesthetic symmetry.

Really the diagram is not complecated.... but I follow you and it would work (should work)
as far as no resistor.. The resistors are on the mobo is the reason you think it doesnt I guess ... but I bought a couple of the 2n2222 NPN's today to play around some... (was getting low on tinkering components lol)

PutWig... You got PM

i am an electronics dummy, but twizted, what is a 2n2222 NPN

Hey Putwig, I just came across this the other day...

Opto-isolation

Hope it helps ya some, more complicated, but a little safer...

Really its no more complicated than useing a 2n2222 NPN Transistor but it is a lil more expensive concidering you cant go to Rat Shack and get a Opto component to meet those requirments.. you would have to order it online and pay shipping.. and unless someone can show me why .. its no more safe than the use of the Transistor based design...

A 2n2222 NPN Transistor is basically a small switch that when activated will allow for highspeed general purpose (medium power) switching of electric current (in this case connecing the ground)...

*EDIT* ok... After thinking about it yeah it is slightly better in therory but the fact is if you know what your doing it is more logical to use the 2n2222 transistor since you can drive to your local rat shack and get it for around .20 and not have to pay shipping on a optoisolator and you can build the circuit much smaller... I have said my peace.. lol... So Peace out!!

Twisted - thanks for everything I really appreciate it! The wiring in your post looks really simple, no reason I can't do it myself!

Is this the piece I need?

http://www.jameco.com/cgi-bin/ncomme...s=503;519;695;

Thanks again!

yes that will work but you can get it as a local radio shack or electronics shop since its a common part...
would save you shipping...
thats it though...

Ordering a bunch of stuff from there ...... so no big deal!

I always thought that this was what optoisolators were for?

The link SportBilly gave above recommended opto-isolators too.

I looked through Jameco and didn't see anything called an opto-isolator. I am about to order a lot of stuff through them, and would like to order from only one place.

The link is:

www.jameco.com

If this piece of kit is at all common, it would seem odd they don't have them! They sell everything!

Edit: just found them here:

http://www.jameco.com/cgi-bin/ncomme...KW&search=opto

here are some: http://www.futurlec.com/LEDOpto.shtml

We must have posted at the same time putwig.