Brief switch controlled indicator LED circuit

Lighting an LED is a simple circuit that is a part of many demonstration circuits.

Brief circuit schematics with short video – List of pages
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Diagram

220Ω or higher resistor will work well with a 5V power supply.

Simple pushbutton switch controlled LED circuit schematic diagram by electronzap electronzapdotcom
Simple pushbutton switch controlled LED circuit schematic diagram by electronzap electronzapdotcom

Video

Quick switch controlled LED circuit schematic to breadboard build

Important topics to understand:

Voltage across LED and protective resistor schematic diagram by electronzap
Voltage across LED and protective resistor schematic diagram by electronzap
  • Voltage must be high enough to light the LED – 5V works well. Too high of voltage might overheat the protective resistor. 12V is about as high as is commonly used, and it is good to use at least 1000Ω (1k) resistor to protect an LED from 12V.
  • LED must be inserted in the right direction (forward biased) in order to light up. The Anode is connected toward the positive side of the power supply, whereas the cathode is connected towards the negative side of the power supply (usually called ground). Anode is usually the longer lead of the component and the Cathode is the shorter lead if they haven’t been cut. Cathode also commonly has a flat edge along the rim.
  •  Current must be limited to no more than 20mA (0.02A) for most LEDs. Good chance it will be plenty bright at 10mA, so don’t try for 20mA all the time.
  • Resistor value is selected to be high enough to limit current to no more than 20mA to protect the LED. I = V/R (current in amps equals voltage in volts divided by resistance in ohms).
  • Resistor also must not overheat. Most are rated at 1/4 watt (0.25W), which should still be limited to not more than 1/8W (0.125W) for extended periods of time. P = IV (Power in watts equals current in amps through a component times the voltage in volts across the component)
  • Forward biased LEDs typically drop about 2-3V of the power supply voltage from reaching the current limiting resistor. You need to subtract that voltage from the supply voltage in order to get a more accurate calculation of the current that will flow.
Next topics

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Kit that has everything you need to learn basic electronics and Arduino.



Nice looking LED kit. Good to have a lot of LEDs because it’s relatively easy to damage them, or to want to use a lot of them in various projects.


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