One of the questions that often comes up with digital circuits is what resistance value should you use with an LED? Well, here I have five different resistors. Here I have a 100 ohm resistor, a 240 ohm resistor, a 510 ohm resistor, a 1 kilo ohm resistor, and a 10 kilo ohm resistor. So you can sort of see the difference. Here we go. Here's an LED. And you can see which is the anode. The anode is the one with the long pin. Here I have each of all of these resistors. The one end is tied in common to power, red lead. The other end on this side of the trough, I have wires going to this bus, which goes to ground, the black lead. So if I connect the LED between these two in the right direction, we see that lights up. Here we go with a 240 ohm resistor. Still quite bright. Here's the 510 ohm resistor. Here's the one kilo ohm resistor. You see it's a little dimmer now. With a 10 kilo ohm resistor, it's very dim. You probably may not be able to even see whether that's on or not. So anything between 100 ohms and 1 kilo ohm is okay for this particular LED. Now how bright it is will depend on the LED. Here we have a green LED. So let's try this. Here we see it with 100 ohms. There we see it with 240. 510. One kilo ohm. And again with 10 kilo ohms, it's too dim to see. Finally. Here's a yellow LED. So again. Here we go with 100 ohms. Nice and bright. Okay. And the right. Nice. 240 ohms. 510 ohms. One kilo ohm. You'll notice with this one, it's a little dimmer with all of those. Even at one kilo ohm, it's not too bright. And again, so 10 kilo ohms. It's pretty much impossible to see. So you see that the choice of resistor doesn't matter that much as long as it's between say about 100 ohms and a kilo ohm. The important thing is that you have it there to limit the current, but the precise value isn't critical.