1. MAKE: AN ELECTRONICS WORKSHOP
SAMI Makerspace
MAKE: AN ELECTRONICS WORKSHOP

2. Relay board
A little electricity can control a LOT of electricity!

3. Why use a relay?
PROBLEM: I want to run something like a motor or lamp that needs more voltage/current than an Arduino can supply. SOLUTION: Use a relay! It’s like an electric switch. A little electricity can open/close the switch, which can be connected to a larger source of electricity.

4. How does a relay work?
At first, the common (COM) and normally closed (N/C) are connected.
A small current flows from A1 to A2
The magnet pulls the switch down, connecting the COM and normally open (N/O).
This creates a magnet in the relay.

5. Safely separated from each other
How does a relay work?
LARGE current from batteries
small current from Arduino
Safely separated from each other

6. Your Relay board 2 pins to provide power to all the relays
4 relays in one!
Screw terminals to securely hold wires!
4 pins to control the relays
Normally Closed (N/C)
Common (COM)
Normally Open (N/O)

7. Controlling the relays with an arduino
Connect the final 4 pins to 4 digital pins on the Arduino
Connect the grounds (GND)
Connect the 5V on the Arduino to the VCC on the relay board

8. Programming the arduino
When the digital pins are HIGH (5V), the relays are “off.” Common (COM) is connected to normally-closed (N/C).
Your digital pins should be initialized as OUTPUT in the setup() function.
When the digital pins are brought LOW, the relay is “on.” Common (COM) will be connected to normally-open (N/O). You will hear a “click.”

9. Example: Blink an LED

10. Blink an LED: The Code Challenges:
Using one relay, have two LEDs alternate between on and off (when one is on, the other is off)
Create a more complicated blinking pattern.

11. EXAMPLE: Run a DC motor in two directions
“B”
“A”
N/C
N/O
COM
COM
N/O
N/C
A = HIGH, B = HIGH : Motor grounded on both sides; no motion.
A = HIGH, B = LOW : Electricity flows from left to right; motor spins.
A = LOW, B = HIGH : Motor spins in other direction.
A = LOW, B = LOW : Motor high on both sides (AVOID)

12. Final warnings!
Be careful not to create shorts. Double check all connections before you add any power, ALWAYS!
A relay can’t be turned on and off too fast. Avoid switching any faster than twice a second.
The coil in a relay can burn out if left on for to long. Always design your circuit so the resting state has no current running through the coil of the relay.