One of the most preferred tools for prototyping electronic circuits is the breadboard, also known as a solderless breadboard. In this guide, you will find the structure of the breadboard, its connection logic, how to use it with elements such as transistors – buttons – relays, and step-by-step answers to the question "which leg do I connect where?"

Basic Structure of the Breadboard

The breadboard allows you to build circuits without soldering wires or components, thanks to its internal structure.

Horizontal Lines (Red/Blue): Usually located at the top and bottom. Red: used as +VCC, Blue: used as GND (ground).
Vertical Lines (Between A–E and F–J): Each vertical column (e.g., A1–E1) is electrically connected. The gap in the middle is reserved for IC (integrated circuit) placement.

Elements Used in the Project (In the Image)

Top row: The 8 black box-shaped elements are probably relays.
Middle row: The 7 black three-legged elements are most likely transistors (BC547/BC337 or similar NPN type).

⚠️ How to Connect Elements Such as Relays, Buttons, Transistors?

1. Relay Connection

Middle 2 pins: Coil ends (connected to VCC and GND)
Side pins: NO (normally open), NC (normally closed), COM (common terminal)
Switching is done with a transistor to power the relay.

⚙️ 2. Transistor (e.g., BC547) Pinout

If the flat side is facing you:

Left: Collector (C)
Middle: Base (B)
Right: Emitter (E)

Connection Logic:

Emitter → GND
Base → Button + 1K resistor to VCC
Collector → Relay coil input

3. Button Connection

One end to GND, the other end to the BASE leg of the transistor via a 1K resistor
When pressed, it provides current and puts the transistor in a conductive state

How to Connect Circuit Power?

A 5V adapter or energy from Arduino should be supplied to the red (VCC) and blue (GND) strips on the edge of the breadboard.
Generally:
- To the red line: 5V (+)
- To the blue line: GND (–)

Sample Circuit: Circuit That Pulls the Relay When the Button is Pressed

VCC (+5V) ─┬────┬─────────────┬────────────┐
          │    │             │            │
        Relay  Button       1K Resistor     Collector
          │    │             │            │
         GND  GND          Base       Transistor (NPN)
                                    │
                                   Emitter → GND

Note: Connecting a diode (e.g., 1N4007) to the relay coil ends is important for safety to ensure the relay pulls.

✅ Tips and Frequently Asked Questions

"How do I place the cables?" → First, install the components, then connect them with colored jumper cables according to the breadboard line.
"Are the legs short or long?" → Elements such as transistors and relays are directional. Refer to the datasheets.
"The relay doesn't make a clicking sound" → The transistor may not be switching correctly, or the relay may not be getting enough voltage.

Conclusion

Although the breadboard may seem complex, it is a very easy prototyping tool when learned with a few basic rules. It is recommended that you first create a datasheet, then a pin definition, and then a breadboard diagram to determine what will come to which leg of which element in your project.