Electronic Circuit Question

[xmastree]

Since there's no power in a rig till the mobo gets on,

There is limited power available from some USB ports. Usually enabled by a jumper on the board.

[slytherock]

There is limited power available from some USB ports. Usually enabled by a jumper on the board.

Nice point, forgot about it, thx

[jbaldwinroberts]

i could power them from an external 240V source straight from the mains coudnt i?? or better off a 9 volt battery as it would take a while to run down?? and be easier to use. i would also prefer this to having another plug into the mains. (i have lots of scrambled wired and plugs already)

i dont understand waht you mean by this as i have absolutely no grounding in electronics

QUOTE
Firstly, a 4017 and a 555 will give you a 'running light' effect.


But... I have a better idea.

Using a 3914 is a bargraph driver chip (similar to a vu meter) which with a bit of additional circuitry can be made to give a nice effect.

If you use your hd activity light to control a RC network (basically charging a capacitor when the light is on, letting it discharge when off) the 'meter' will start at zero and rise to 100% as the disk is accessed. The flashing of the normal light will become a 'bouncing' of the meter (think - vu meter again).
QUOTE

could you explain what you mean in simpler terms or give me some good websites to give more info.

thanks alot

Joe

[xmastree]

Hmm... LM3914.

Imagine an LED vu meter, you know the thing? The 3914 is the driver chip which controls these. I'm suggesting that you use a similar device to drive the LED's around your switch.
Something like this but without the sensor thing they use.
If you have a local electronics hobby shop, they might have a similar kit. If you can, make sure it's not a vu meter kit, as they have a different response.

Now, the LED's will light up proportional to the voltage input to the circuit, so you need to generate a voltage which rises and falls with the disk access.
That's quite easy, you can use a transistor switched by the HDD header, and charge a capacitor with it.

[jbaldwinroberts]

Why cant i just use this circuit here or is that what you are suggesting?? as the vu meter idea would just make more leds light up the more activity whereas i want them to rotate. this circuit guide here seems to do this. i think i know which two circuits i want to use to do the 2 things i need but i just need to know how i can join them so that they can both control the same set of leds and so that the key switches one circuit on and so that the power button switches one circuit on and one off.

i found a good little hard drive chaser circuit here
http://metku.net/index.html?sect=vie...lot2/index_eng
but i would need to change it to workonly when the computer is on not when the key is turned.

i also found a cricuit to make the leds pulse that i would connect to the key switch so thay would run when the key is turned. i would also need to change this so it stopped when the computer is powered on. would this circuit work??
http://metku.net/index.html?path=mod...fade/index_eng

thanks for any help, and do you think these two circuits could work together.

[xmastree]

Why cant i just use this circuit here or is that what you are suggesting??

You can, and that seems to be just what you are looking for. See my first post about a 555/4017 circuit, that's it.

The vu idea was just an alternative approach, that's all.

[jbaldwinroberts]

ok, well i think i am going to stick with my idea, but thanks for the input. it gave me an idea that i could put a vu meter on the side of my case or somewhere that would be connected to my speakers. maybe another project for after this one.

thanks

[jbaldwinroberts]

any idea how i would join these 2 circuits up then??

[slytherock]

Told you; I'm moving, give me a couple of days

[jbaldwinroberts]

Ok thanks, sorry for being impatient