The Official PC building thread - 4th Edition

Just discovered that the LED's are sensitive in a certain way. There are apparently positive and negative terminals on the lights. And it's critical that they are connected accordingly. Not usually so with 12V bulbs. Not sure if the voltage has something to do with this. Wouldn't think so. At least I discovered this BEFORE I hot glued everything back in place. I would have been screaming and yelling LOL!

This is what I've done. Sorry its blurry. When I zoom with my camera, clarity goes out the window LOL! It'll be different in the future. Probably solder, than hot glue. I got lazy.

I was testing them, and they were not lighting up. I thought somehow the use of the solder gun blew them. Much like welding without proper grounding? In any case, I reversed the wiring and all was well. Apparently positive and negative connections are critical. So I'll be wiring them, while the computer is running...

 

Diode = Current only flows one way. Basic electronics

 

LOL! Whoops! Showing my true colors again Nah, there's still much I don't know...

 

Wow, I feel like I'm back in school today. L-E-D. Light Emitting Diode. I understand the function of a diode. I never thought to look up LED. Just passed it off as a new form of light, I guess. Silly silly LOL!

I just may begin modifying my HAF in the near future. Not sure. Looks like Radioshack.com sells the L-E-D's in bulk too. In the non hot glued fashion If newegg does, that would be new to me. I searched around for a while, before purchasing what I did. They certainly should sell them in their basic unused form factor!

 

Basic LED Principles:

-> LEDs conduct in one direction only. IIRC, the negative pin is the shorter leg.
-> LEDs are non-ohmic, they will drop a fixed voltage unless forced.
-> Typically LEDs drop 2-2.5V and have a typical If of about 20mA. Thus, you need to use a resistance in series with them that causes the appropriate amount of current.

for example:
12V supply
2.5V voltage drop
30mA forward current

12V-2.5V = 9.5V
9.5/30x10^-3 = 316.66Ohms minimum resistance, nearest value would be 330.

 

Oman7,
I thought you knew that they were Diodes! That's what the "D" stands for in LED (Light Emitting Diode). Diodes only pass current in one direction!

Russ

 

LOL! I know that now russ.

Thanks sam. Valuable information. I guess we'll see what happens :S

The thing is, the device I bought:
This one
It Did have obvious resistors(it would need them, due to 12V molex input), but I don't believe the stock LED's in my tower did. I think they're being fed what they need. Perhaps off the 5v rail. Or a different rail, regulated by the mobo. Which would be whatever the Fpanel puts out...

Wish I had a voltage meter. Then I could determine exactly what the Fpanel puts out

 

You think the F_panel is universally 5V then?

If that's true, than the LED's are only getting slightly more than their requirement. Which allows them to be brighter. At probably a slight cut in life...

I knew there was a reason I love this thread! xD

 

Oman7,
Typically, most LEDs require less than 2v DC. They can handle about 5v, maximum, before blowing out, although I don't recommend it. You could also daisy-chain about 8 of them in a series circuit (+ to -, + to -, and so on, and use the 12v DC from the PSU fed to each open end. If that isn't bright enough for you, you could use 7 instead, for a bit more brightness, or 9 for a bit less. The down side to the Series circuit is that if one LED dies, the whole string goes out.

Russ

 

That's one of the first things I learned about basic electronics. Wiring in series. 2 12v batteries in series = 24V, and so on. I hope that isn't the way it was wired stock. I guess I'll find out when/if I pop the led's...

 

Typical cheap large LEDs have a 2V voltage drop. Smaller ones may be less. Typically bright blue/purple/white ones have higher than 2V.

 

I'm hoping that this is their specification. But not all 5mm leds are the same?????
http://www.radioshack.com/product/index.jsp?productId=3107633

 

Notice as it's a UV LED the Vf is 3.2-3.8V.

 

Do you think they would survive ~5V, or is that over doing it. 25% overvolt does seem extreme.

 

No, if it says 3.8V max I wouldn't expect them to survive 4V for long, let alone 5V. Even if they did survive, with no current limiters you'd probably fry them anyway.

 

Man...I'm buying a voltage reader today. It's the only way to be 100% certain. I've wanted one for a long time anyway If I don't, I'm calling MSI to know EXACTLY what the damn wires are reading...

 

I wonder if they're getting the other typical voltage. 3.3V. Lets find out! I just got my voltage meter. P.S. I did not shop this. I would have done a better job
Here it is:


I may consider these LED's next time. 7 colors rolled into one is pretty intriguing. I could be into that xD
http://www.radioshack.com/product/index.jsp?productId=3060680&clickid=prod_cs

Uh oh... It looks like the power source on the board may be wonky LOL! It reads ~.8V, and 14.5ma. And since the previous blue LED's took a long while to power up, I'm forced to conclude that the voltage output is unstable. I have gotten 4 yrs out of that tower. Can I really complain? I'll check it again in an hour.

 

Oman7,
It's interesting, I clicked on the roll of Solder, right under the 7 color LED, and happened to notice that it was 60% Tin and 40% lead, while the Solder I get from my local independent electronics store is silver based and is 100% lead free! I thought that lead was out for good!

Russ