Image from www.btinternet.com
This is not going to be a long post, and maybe not even that interesting, but it is important. There are lots of applications for an LED, and it seems that it is a good starting point for the new DIYer. It is supprisingly how much trouble people have with them, but it is understandable. If you connect an LED straight to a 9v battery, you will then only have a pretty little plastic dome with two wires coming out, and some pretty blue smoke.
Anyway, it is important to be able to tell which lead is ground. The long lead is the anode, which is connected to your positive voltage (Vcc). The short lead is the cathode, which is connected through a resistor to the ground.
How do you tell if the leads have been cut? Well, I have a simple way of remembering this. If you look closely inside the LED, you will see where the leads go inside of the plastic. One of the leads will be bigger and more horizontal. In my mind it looks like a “-” sign. This is your ground lead. In the above picture, it would be the lead on the right.
2 Responses to “Which LED lead is Ground?”
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Really. I have never seen one that way. That is interesting. Well, I guess it is not a fool proof plan, but it is a “general” guideline. You could always just put a small voltage on it, and flip it around until it turns on. Honestly, that is what I do
Now, I have a bigger question. If you find a bucket full of LEDs, I do not know how to figure out the voltage rating for them. How do you decide the resistor value for an LED when you don’t know the LED values? There has to be a way, if anyone knows then leave a comment.
Oh and Brandon, all you have to do for the IR LED, is you could build a detector circuit that was permanently mounted, with a transistor, and another regular LED. You could shine your infrared LED at your new circuit, and if it is on, your circuit would turn on the visible LED. It would be kind of a checker. That way you would know if you accidently fried your IR LED. (Which I have done several times sadly)