УРЛАГ
ГОО САЙХАН БА ЭРҮҮЛ МЭНД
ГАРААР ХИЙСЭН
СОЁЛ БА ТҮҮХ
ҮЗВЭР НААДАМ
БАЙГАЛЬ ОРЧИН
ХООЛ БА УНДАА
НОГООН ИРЭЭДҮЙ
УРВУУ ИНЖЕНЕРЧЛЭЛ
СУРГУУЛИЙН ТӨСӨЛ
ШИНЖЛЭХ УХААН
СПОРТ
ТЕХНОЛОГИ
ӨМСДӨГ ХЭРЭГСЭЛ
Using Relays — SIK Circuit 13
Ed

Зохиогч

Ed

17. Гуравдугаар сар 2026FI
70
0
0
0
0

Using Relays — SIK Circuit 13

Control a relay with a transistor to switch between two LEDs. Learn about electromechanical switching, SPDT relays, Normally Open vs Normally Closed contacts, and flyback protection.

Зааварчилгаа

1

Parts & Introduction

A relay is an electrically-operated mechanical switch. A small current energizes a coil that physically moves a contact arm, switching a separate circuit. Relays can control high-power devices (motors, lights, appliances) from low-power Arduino signals. This experiment uses an SPDT (Single Pole Double Throw) relay to alternate between two LEDs.

Parts Needed

  • 1x Arduino Uno + USB cable
  • 1x Breadboard
  • 1x SPDT Relay
  • 1x NPN Transistor (P2N2222A)
  • 1x Diode (1N4148)
  • 2x LEDs (different colors)
  • 2x 330Ω Resistors
  • 14x Jumper Wires

Materials for this step:

SparkFun Inventors Kit - V3.2SparkFun Inventors Kit - V3.21 багц
Arduino Uno R3Arduino Uno R31 ширхэг
BreadboardBreadboard1 ширхэг
SPDT Relay1 ширхэг
NPN Transistor (P2N2222A)NPN Transistor (P2N2222A)1 ширхэг
Diode (1N4148)Diode (1N4148)1 ширхэг
5mm LED5mm LED1 ширхэг
330 Ohm Resistor330 Ohm Resistor2 ширхэг
Jumper WiresJumper Wires8 ширхэг

Tools needed:

Computer with Arduino IDE
2

Hardware Hookup

Wiring Instructions

Transistor + Relay Coil
  1. Connect transistor Base through 330Ω resistor to Arduino Digital Pin 2.
  2. Connect transistor Emitter to GND.
  3. Connect one side of the relay coil to transistor Collector.
  4. Connect other side of relay coil to 5V.
  5. Flyback Diode: Band (cathode) to 5V, anode to Collector.
Relay Contacts + LEDs
  1. Connect relay COMMON through a 330Ω resistor to 5V.
  2. Connect relay NC (Normally Closed) to LED 1 positive leg.
  3. Connect relay NO (Normally Open) to LED 2 positive leg.
  4. Connect both LED negative legs to GND.

Materials for this step:

SPDT Relay1 ширхэг
NPN Transistor (P2N2222A)NPN Transistor (P2N2222A)1 ширхэг
Diode (1N4148)Diode (1N4148)1 ширхэг
5mm LED5mm LED1 ширхэг
330 Ohm Resistor330 Ohm Resistor2 ширхэг
BreadboardBreadboard1 ширхэг
Jumper WiresJumper Wires8 ширхэг
3

Arduino Code

Open the Arduino IDE and upload the following sketch to your Arduino board.

relay.inoarduino
/*
SparkFun Inventor's Kit
Example sketch 13 — RELAYS

Use a transistor to drive a relay, alternating two LEDs.

Hardware connections:
  Transistor BASE through 330 ohm resistor to digital pin 2
  Transistor EMITTER to GND
  Relay coil: one side to COLLECTOR, other to 5V
  Flyback diode: band to 5V, anode to COLLECTOR
  Relay COMMON through 330 ohm to 5V
  Relay NC to LED 1 positive, Relay NO to LED 2 positive
  Both LED negatives to GND

This code is completely free for any use.
*/

const int relayPin = 2;
const int timeDelay = 1000;

void setup()
{
  pinMode(relayPin, OUTPUT);
}

void loop()
{
  digitalWrite(relayPin, HIGH);  // Relay on (COM connects to NO)
  delay(timeDelay);

  digitalWrite(relayPin, LOW);   // Relay off (COM connects to NC)
  delay(timeDelay);
}

Materials for this step:

Arduino Uno R3Arduino Uno R31 ширхэг

Tools needed:

Computer with Arduino IDE
4

Test & Experiment

What You Should See

You should hear the relay clicking, and see the two LEDs alternating — one on, one off — switching every second.

Troubleshooting

  • LEDs not lighting: Check LED polarity — longer leg is positive.
  • No clicking sound: The transistor or coil circuit isn't working. Verify transistor orientation and coil connections.
  • Relay not making good contact: The SIK relay is designed for soldering, not breadboarding. Press it firmly to ensure all pins contact.
  • Confusion: Don't mix up the TMP36 temperature sensor with the transistor!

Experiments to Try

  • Replace the LEDs with a motor on the NO contact — use the relay as a motor on/off switch.
  • Use a button to control when the relay toggles.
  • Add variable delay to create morse code patterns.

Материал

9

Шаардлагатай багаж

1
  • 13
    Computer with Arduino IDE
Estimated Total
$181.00

You can swap these in

Can't get one of the materials? Swap it for an equivalent — these work just as well.

Recommended for this build

Products makers often use with builds like this one.

Servo MotorUsed together and in similar builds
Resistor 10K Ohm 1/6th Watt PTH - 20 packUsed together and in similar builds
DC MotorUsed in similar builds
Push Button - 33mmFrequently used with this build's materials
Temperature SensorUsed in similar builds
Flex Sensor 2.2 InchUsed together and in similar builds
LED - RGB Diffused Common Cathode - 5mmFrequently used with this build's materials
USB CableFrequently used with this build's materials

Related blueprints

Other builds that share materials, tools, or techniques with this one.

Using a Flex Sensor — SIK Circuit 9electronics/electromech1 shared material
Driving a Motor — SIK Circuit 12electronics/electromech1 shared material
Driving a Servo Motor — SIK Circuit 8electronics/electromech1 shared material
Reading a Temperature Sensor — SIK Circuit 7electronics/electromech1 shared material
Flex Sensor Glove — Control 5 Servo Motors with Hand Gestureselectronics/electromech1 shared material
Using an LCD — SIK Circuit 15electronics1 shared material

CC0 Нийтийн домэйн

Энэ загвар CC0 дор гаргагдсан. Та зөвшөөрөл авахгүйгээр хуулах, өөрчлөх, түгээх, ашиглах боломжтой.

Загвараар дамжуулан бүтээгдэхүүн худалдаж авч Бүтээгчийг дэмжээрэй Бүтээгчийн шимтгэл Борлуулагчаар тогтоосон, эсвэл энэ загварын шинэ хувилбар үүсгэж орлогоо хуваахын тулд өөрийн загварт холбоос болгон оруулна уу.

Хэлэлцүүлэг

(0)

Нэвтрэх хэлэлцүүлэгт нэгдэхийн тулд

Loading comments...