Okay, let's say that you follow the instructions for the simple switch circuit
and you've gotten to the point where you're ready to turn your LED on
and you go to press the button and the LED doesn't turn on
The first thing you want to check is your power supply. You want to make sure that you have the orientation of your terminals from your battery snap connector
connector or in the correct position or the correct orientation or in the correct rails where you want your positive and negative side on your breadboard
So in this case we can see that from the battery snap connector this black wire here is going to this point in my circuit
But in this point in my circuit, I needed to designate this section as my positive supply here, but I have my black wire or my negative supply going into where I need my positive supply
And alternatively, you can see that our red wire, which is designated as the positive supply of the battery
is going to where I need to designate my negative supply. So I have these two terminals coming from the battery snap connector to my power source in the wrong orientation
So I need to switch them. So now I have the red wire or the positive lead from the battery
from the battery snap connector going to my positive supply rail of my breadboard and now I have the negative lead coming from the battery snap connector going to our negative rail of the breadboard. So now if I press the button, we see that the LED now comes on
But let's say that there was something else going on that you weren't aware of. And let's say that
you checked over your power supply and you noticed that your positive supply is going to your
positive supply rail and your breadboard and your negative supply is going to your negative
rail of your breadboard but you go to press the button and your LED is not turning on The next thing that you need to check is the LED itself An LED is a diode so it only allows for the flow of current to go in one direction in the circuit
So to determine whether or not you have your LED in the correct orientation is by looking at the LED itself
If you look closely inside, if you can, inside the dome of the LED, in this case I at least
we have a red LED, you can see that there's a larger terminal inside
And to me, it looks kind of like a flag. And I always consider that terminal the fat flag of the LED
So when I look at an LED, if I'm able to see inside the dome
and I see this fat flag in there, then that tells me that this is the negative side
or the cathode of the LED. So in this case, if I get my tweezers here, so my fingers aren't in the way
in this case, if you look inside, I can see the fat flag is on this side
which is connected to this terminal here. And that tells me that this leg of the LED is the negative or the cathode of the LED
Also, if you look in an LED, if the leads have not been cut off, you can determine the anode or the positive side of the LED by the longer leg of the LED
This leg is bent right now, but if it were straightened out, this leg here would be longer than this one
So this leg here tells me that this is the positive lead of the LED
So if I place the long leg here of this LED, the long leg is the long leg is the positive or anode of the LED
if I place it where I need it to be in connection to the resistor
and I place the shorter leg or where the fat flag is
the shorter leg, my negative lead or cathode, and I place it into my negative supply
then that would show me that the LED is. in the correct orientation So now if I press the button the LED lights up
But let's say that your power supply terminals are correctly connected to the positive
and negative rail of your breadboard, and let's also say that your LED is in the correct
orientation according to our circuit here. but you go to try to press the button of the circuit and the LED does not turn on
So now you need to start looking at how your components or your jumper wires, how they're connected within the circuit
as I was talking, I moved this jumper wire just from this hole or point on the positive supply of the breadboard into this point or onto the negative supply of the breadboard
If you weren't paying attention, and I've done this many times, if you weren't paying attention, you could accidentally be putting one end of a jumper wire in an incorrect point on the breadboard
And it's not connected to, in this case, the positive power supply
So there's no positive supply coming into our circuit to continue the connection to ground
So if I were, so we can see that the LED is not lighting up
If I were to just move my jumper into that point and make sure that the other end of the jumper is in line with the leg
leg of this push button. If I now press the button, the LED lights up. So I wanted to make
sure in this case that this side of the jumper wire is in connection with my positive
supply in order to continue the circuit to the switch, through the switch, and through the
resistor from the resistor through the LED and from the LED back to ground
The same goes for the resistor. Let's say that the resistor had somehow been placed in this orientation and we weren't
paying attention. We can see that this leg of the resistor is not in line Let me get this is not in line with these holes here Because on a breadboard these holes are connected but these holes here are not connected to these holes
And we can see that this lead of the resistor on this side is not connected to the switch on this end
and also in this case this side of the resistor, this terminal here, is not in line with the LED, which should be here
So if I, let me get this closer. If I were to place this lead from this hole to this hole and place this lead from this hole to this hole and place this lead from this
hole to this hole in line with the switch. Let me see. We can see now that this
leg of the resistor is in line with the LED with the anode of the
LED and we can see that this leg of the resistor is in line with the switch here
So now if I place my power supply back, we can see that if I press the button, the LED lights up
So you want to check your placement of your jumper wires, your placement of your resistor
your placement and orientation of your LED. And remember that the orientation of the resistor
doesn't matter. So the orientation it's currently in now. Let me zoom you in here. The orientation
the resistor is in now, the LED lights up. If I were to switch the orientation of the resistor
I'm turning it around. And placing it back. in the circuit and I press the button you can see the LED still lights up. So if you check
these common mistakes you can soon figure out what your issue is and hopefully get your
LED to light up