Relays (CIRC11)

Purpose
The purpose of this circuit is to explore the role of a relay.


Equipment

• 1 x Transistor
• 1 x Relay
• 1 x Diode
• 1 x 560 Ohm Resistor
• 1 x 2.2K Resistor
• 2 x LEDs
• 14 x Wires
• 1 x Arduino Uno
• 1 x Breadboard & reference sheet

Program Details

     Assembling this circuit takes up to around 7 minutes. There are a lot of important pieces besides the wires that need to be placed correctly. Some of these pieces have been used before, however it is still important to know how each piece functions to understand the circuit. The diode allows one way current flow, and the transistor either switches or amplifies current. This function is similar to the relay which acts as a switch for even large amounts of current. Since we're working with a lot of current the resistors are stronger as well. Below & beside are pictures of assembled circuits. 

     The code for the following circuit is as straightforward as blinking. In fact it follows the same format except instead of turning the LED on and off directly. We send the message to the pin connected to the relay. The LEDs are connected to the relay as well, so we're using one pin to control the bulk of the outputs. 

Results

     

     The LEDs worked fine, as instructed by the program. It did seem some what underwhelming, however I can imagine that it more LEDs were added it'd be pretty significant. This would be a good next step.

Tips

     The only important tip with this circuit is to connect the relay properly. If one of its 3 pins aren't connected properly, it won't function. Also make sure the wire that connects the relay to the Arduino board is connected to pin 2 on the Arduino board. 

Next Steps & Associated Modifications

     A simple addition would be to connect more LEDs to the circuit (specifically to the relay). This way we can see how useful the relay really is. The program code for this stays the same. However this circuit isn't simply limited to LEDs, try a motor! Or even the piezo element! The code that can be applied to basically all these outputs is explained below.

int ledPin=2; //the relay is connected to pin 2

void setup()

{ pinMode (ledPin, OUTPUT); } //make it so the relay sends output to LED

void loop()

{

  digitalWrite (ledPin, HIGH); //turns LED on via relay

  delay (1000); //wait a second

  digitalWrite (ledPin, LOW); //turns LED off via relay

  delay (1000); //wait a second before repeating this blinking effect

  

}

References:

1. Spark Fun Inventor's Starter Guide

2. http://www.oomlout.com/a/products/ardx/circ-11