Circuit Activity Board

Hi everyone! In this project, I want to show you a Circuit Activity Board. It's a fun little project I designed myself and it's perfect for anyone who wants to explore the basics of circuits, whether you're a maker or a teacher looking for a hands-on way to teach your students some STEM concepts.

Step 1: Overview

So, what exactly is this Circuit Activity Board? Well, it’s a simple, interactive way to learn about circuits. On this board, we have three main components: a Light Dependent Resistor (LDR), a LED, and a Buzzer. Each of these can be controlled using these 3D-printed ‘switches’ here. These are basically little levers, but you can think of them as keys to unlock the different circuit components.

Step 2: Materials Required

To build the Circuit Activity Board, you’ll need the following materials:

• Printed Circuit Board (PCB)
• 1x Light Dependent Resistor (LDR)
• 1x LED
• 1x Buzzer
• 1x CR2032 3V Battery and Battery Holder
• 2N2222 Transistor
• 27k and 220-ohm Resistor
• 10uF Capacitor
• Copper Tape
• 3D-printed switches
• 3mm bolts and nuts
• Soldering iron and wire

PCBWay was chosen for the PCB fabrication. You can find the Gerber file and circuit diagram for PCB fabrication at this link - https://www.pcbway.com/project/shareproject/Circuit_Activity_Board_Educational_Electronics_b729c8f4.html

Also, if you have no soldering experience, you can use PCBWay's assembled PCB service. I also participated in PCBWay's 7th design contest, if you want to support the project, you can vote from the same link. Thank you.

Step 3: Circuit Overview

The circuit design revolves around an LDR (Light Dependent Resistor), an LED, a buzzer, and a 2N2222 NPN transistor. A 3V battery powers the board. Let’s break down the components and their connections:

• LDR (Light Dependent Resistor) – The LDR (U2) detects the light levels. As light decreases, its resistance increases, triggering the next part of the circuit. The LDR is paired with a 27kΩ resistor (R1) to form a voltage divider, which controls the base of the transistor.
• Transistor (2N2222) – This NPN transistor (Q1) acts as a switch. When the voltage from the LDR divider reaches a certain threshold, it allows current to flow from the collector to the emitter, powering the LED and buzzer. The transistor ensures that the LED and buzzer operate only when needed.
• LED (LED1) – Connected to the collector of the transistor, the LED lights up when the LDR detects low light levels, signaling that the circuit is active.
• Buzzer (LS1) – This component emits sound when the transistor switches on. The buzzer is in parallel with the LED, meaning both components activate together when the circuit is triggered by the LDR.
• Capacitor (C1) – A 10μF capacitor is placed across the power lines to help stabilize the voltage and prevent fluctuations from affecting the buzzer and LED.
• Resistors – There are two resistors in this circuit: a 220Ω resistor (R2) limiting the current through the LED and a 27kΩ resistor (R1) as part of the voltage divider with the LDR.
• Switches – There are several switches in the circuit diagram (SW1, SW2, SW3), which represent user-interactive components that can be used to either reset or adjust the circuit's operation.

Step 4: 3D-Printed Switches

Now, these purple levers that you see were printed using a 3D printer, and I added copper tape underneath to help complete the circuit. They’re mounted onto the board using 3mm bolts and nuts, and they have an important job – they act as switches to complete the GND line of the circuit. Imagine them as bridges that help electricity flow through the circuit and activate the components.

• Begin by printing or sourcing three 3D-printed levers. These will act as switches for your circuit.
• Attach copper tape underneath each switch to ensure electrical conductivity. The copper tape allows the switches to complete the GND line in the circuit.
• Mount each switch onto the board using 3mm bolts and nuts. Each switch should have a 3mm hole for the bolt to pass through.
• These switches will be responsible for completing different sections of the circuit, like a traditional electrical switch.

Step 5: How It Works

1. First Switch – Power Control:

Let’s dive into how this works! The first switch, which is on the right, acts like an ON/OFF switch. It’s connected to a CR2032 3V battery on the back of the board and controls the GND connection for the rest of the circuit. So when this switch is flipped to ON, it essentially powers up the whole board, making the other switches functional.

2. Second Switch – LDR Activation & GND Bridging:

The second switch, here in the middle, has a bit more going on. It actually does two things:

• First, it completes the GND line for the third switch, which we’ll get to in just a moment.
• Second, it activates the LDR (Light Dependent Resistor). The LDR is now ready to detect light levels, and based on the position of the third switch, it will either trigger the LED or the Buzzer. But here’s the catch – it only works in the dark! When the LDR senses low light, it allows the third switch to activate the selected component."

3. Third Switch – LED/Buzzer Control:

Now, let’s move on to the third switch, the one on the left. This one is connected to both the Buzzer and the LED, but only one will be activated based on how you position this switch. If the middle switch completes the GND line and the LDR detects darkness, flipping this third switch will either light up the LED or sound the buzzer. It’s like a simple decision-maker for the circuit!

And that’s it for the Circuit Activity Board! I hope you found this project as fun as I did. If you’re looking for a simple but effective way to teach or learn basic circuits, this is a great project to try. Let me know in the comments if you have any questions or ideas on how to make it even better! Thanks for reading, and don’t forget to like and follow if you enjoyed this article. See you in the next one!