Basic LED circuit controlled with momentary tactile push button switch on a breadboard
Lighting an LED and being able to turn it on and off with a switch sounds simple enough, but when studied carefully, this circuit reveals a lot of electronic properties involved in all electronic circuits.
I am working on a video where I build this circuit on a breadboard. I will be covering all the components in detail and taking multimeter measurements.
Component topics that will be covered:
- Electronics prototype circuit breadboard – A board that makes electrical connection by inserting through hole components leads into.
- Breadboard power supply – Easily plugs into a standard breadboard. Takes a higher voltage at it’s female barrel plug input and converts that voltage to either 5V or 3.3V, which it outputs to the breadboard power rails, marked with red for positive, and blue for negative.
- Outlet plug (wall wort) – Plugs into the household outlet (120V alternating current in the US) and outputs a lower DC voltage via a male barrel plug. The outlet plug I will be using has a range of voltages it can output. I will probably keep it at 9V.
- LED (Light emitting diode) – A diode that lights up. Being a diode, it conducts current easily in one direct (usually at about 2V) and blocks current up to an unknown voltage (probably a bit more than 9V). Easily conducts while forward biased (Andode more positive than cathode) and blocks current while reverse biased (anode more negative than cathode). Most through hole LEDs should have current limited to 20 mA (milliamps) or less.
- Resistors – When the switch is turned on, the resistor will be the only component in this circuit that limits current through all of the series components. The amount of current in amps will be the voltage across the resistor, divided by the amount of resistance the resistor provides in units called ohms, based on the Ohms law formula I = V/R. Since there will be a lot less than 1A of current, it will be converted and referred to in milliamps. Resistors create a lot of heat and can dissipate it based on their wattage rating. Most resistors are 1/4W resistors and schematics usually assume you will use 1/4W resistors unless it labels the resistor’s schematic symbol as a different wattage.
- Normally off momentary tactile push button switch – Normally the switch will prevent all current from flowing due to high resistance, but when you press the switch, it will make a almost 0 resistance connection that will allow full transfer of power throughout the circuit.
List of topics that will probably be covered in video:
- Prototype breadboard introduction
- Breadboard MB102 0V, 3.3V or 5V power supply introduction. 6.5V-12V input, with 9V recommended.
- Providing power to breadboard power supply
- Measuring voltage of power supply with a multimeter
- Resistor component introduction. 1/4W kept below 1/8W and heat dissipation. Resistance (R), voltage (V) and current (I) measurements with multimeter
- LED component introduction. Forward and reverse biased V drop measurements with multimeter. V and I measurements. 20mA maximum recommended forward current.
- Momentary tactile push button switch introduction. Almost infinity ohm (Ω) resistance (insulator) when off and almost 0Ω ohm (conductor) when on demonstration.
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