Concept of Operation

The circuit demonstrates the use of a momentary push button switch. This is one of the simplest circuits and a good first circuit for a new electronics student or enthusiast to try.

The switch is connected between a battery (or other power source) and a light emitting diode (LED). The circuit also includes a resistor to limit the current flowing through the LED.

The momentary switch is "normally open" meaning that when the button is not pushed there is no electrical connection made. When the button is pushed, the switch is closed, completing the circuit and lighting the LED. When the button is released the switch opens and the LED turns off.

Schematic

Breadboard Diagram

Parts

• 330 Ohm Resistor (x1)
• Standard LED (x1)
• Tactile Pushbutton Switch (x1)

(All parts for the project are available in our store.)

Notes on Implementation

1. LEDs are polarized and must be mounted in the proper orientation. On standard, round LEDs, the cathode (negative lead) is identified by a flat edge. Also, the cathode lead is typically shorter than the anode.
2. The tactile switch must also be mounted in the breadboard in the proper orientation. Although the typical switch used here comes in a square package, the spacing of the leads is wider in one direction (5mm) than the other (3mm). When oriented correctly, the leads will span the gap down the center of the breadboard and fit easily into the holes. When oriented incorrectly the leads will be too narrowly spaced and will not span the gap.
3. The circuit was built and tested at 4.8 volts DC (4 AA NiMH rechargeable batteries). Any power source that supplies about 5v DC should work fine.