SWITCH INTERFACE ON 8051

SWITCHES

Switches come in many different shapes and sizes. The main idea or function is to either enable or disable something by simply turning it on/off. Thus it acts as an input device that users can use to control certain parts of the system. Below are the most common switches that you will come across

Push Button

ON-OFF Switch

In circuit diagrams, a switch is generally represented by 

Switch Symbol

After examining the Switch Symbol, I think it is quite clear how a switch actually works. It closes (connects) or opens (disconnects) a circuit. The Push Button behaves in the same fashion as it closes the circuit as long as you keep holding it in pressed state.  

SWITCH INTERFACE CODE

Here is the C language code for the Switch Interface with the 8051 microcontroller-

SWITCH Interface C Language Code

Let me explain the code in a step wise fashion

• PIN1.0 is renamed as sw using  (for convenience)
• Similarly PIN1.1 is renamed as led (LED is connected to this pin)
• sw is declared as input pin (for reading switch status)
• led is declared as output (for driving LED on/off)
• if ( !sw ) statement is true only if switch is ON (sw = 0 and !sw = 1) and thus led will glow
• Otherwise led will stay OFF

The same code simulated in Proteus looks like this -

Proteus Simulation

This concludes the topic for today. I hope that after reading this post, you have at least some basic idea of using a switch with the 8051 microcontroller.