About the Pushbutton LED Circuitthe way the push button works is that when you push the button, it turns the open circuit into a closed circuit. when the button is NOT pushed, it isn't a closed circuit, so the LED doesn't turn on.
How Buzzer Circuit WorksWe made a complete circuit from the positive bus to the buzzer then to the lower negative bus. Then we connected it to the resistor so the alarm would not be as loud. After that we connected the negative wire to the resistor to for a complete circuit.
PNP Transistor ReviewIf the base prong is connected to the negative battery wire, it will be turned off, lighting up the LED. If the base prong is connected to the positive battery wire, the transistor will be on, turning off the LED.
How the PNP works with the capacitor to brighten the LEDThe PNP is the switch that controls whether the LED lights up or not. If the PNP DOES have charge on its middle leg, then the LED will NOT light up. If the PNP DOESN'T have charge on its middle let, then the LED WILL light up. The capacitor is what controls whether or not there is charge on the middle leg of the PNP. While the capacitor is filling up, it's also leaking charge through to the middle leg of the PNP. At the beginning, when the capacitor is almost empty, it's leaking a lot. When it's nearly full, it's only leaking a little bit. When it's totally full, it stop leaking. So as the capacitor fills, less and less charge gets through to the PNP's middle leg. So the PNP goes from being totally off, to a little bit on, to being totally on. That's why the LED gradually lights up.
How does the reed switch workThere are two small, leaf-like tabs of metal inside the reed switch. By default, they are separate when the switch is closed. But when the bolt is applied to the surface of the glass bulb, the metal tabs merge, thus opening the switch, and turning on the light bulb.
How does the bi-color LED circuit workWhen two resistors of opposite voltage meet, the voltage is approximately the middle of the maximum voltage the batteries can apply.