Need help turning pc speaker into LED

I had this great little idea of using a LED in place of the PC speaker. This way it would blink, instead of beeping on startup or when errors occur.

Where i need help is, does the PC speaker connections/pins sends some extra wattage that would burn up a regular case LED? Or would it work at all? I mean do the connections check for a specific resistance or response signal only PC speakers can generate?

A resistor in series might do the trick as one of the pins is +5V.

While I like the idea, you probably won't be able to notice the difference between a high or low tone, you could of course use a switch to switch between the LED and speaker in case something is wrong.

**EDIT** I'll do some testing to see if it works.

If your handy with electronics, I bet you could make something with 2 different color LEDs. Use one for the high and one for the low tone. I don't know how that would work though. I like your idea jae.

You could try to create hi-pass and low-pass filters connected to different leds. It would take a great deal of trial and error, and may be more troble than it's worth, but it should work.

jae87 said:

Correct me if i'm wrong here, but isn't the motherboard only sending higher or lower current to make the high/low tones? So in theory the led will either blink bright or dim .. no?

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No, the frequency at which, either the polarity changes, or the rate of pulses determines the pitch of the sound, pulsing at a higher rate or changing the polarity at a higher rate will produce a higher pitched sound.

I estimate the frequency that a MOBO produces is around 1KHz, meaning that the polarity changes 1000 times per second, or that the spearker receives 1000 pulses per second.

The difference between pulses and changing polarity is:
1) Pulses will only move the cone in one direction.
2) Changing polarity will make the cone move in both directions.
When a cone moves in both directions the excursion will be bigger, thus it'll be able to move more air making it sound louder.

jae87 said:

200 mili ohm resistor (i think it was mili ohm)

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That can't be right, use Ohm's Law (V(Voltage)=I(Amperage)*R(Resistance)).
A few numbers are given (Example):
1) Output Voltage=5V (Vo).
2) LED Voltage=2V (Vl) (Depending on the type of LED).
3) Amperage=0.020A (20mA, suitable for most LEDs).
Now we need to know the voltage drop (Vd), Vo-Vl=Vd thus 5-2=3.
So the resistor should drop the voltage by 3V @ 20mA, 3/0.020=150 Ohm.

Of course it's easier to use a calculator like this

jae87 said:

KILLorBE, how did your testing go? I like the switch idea, something to think about.

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Sorry, I haven't had much time (I've spend 20+ hours to recover data from yet another dead 60GXP , I also bought some old crap on Ebay that I had to test).
I'll do some testing tonight or tomorrow, I'll also see if I can come up with a simple and easy to use/build high/low pass filter (There are several problems that I need to take a look at, it has to be adjustable as not all MOBO's are the same (The frequency may vary), I need to simulate errors...I've been thinking about using freesco, or an old program that'll play music through the PC speaker....but it may take a while).

It works, I hooked up a 4V blue LED with a 47 Ohm resistor, and when you're supposed to hear a beep the LED blinks.

Of course you should try it at your own risk.