My Ambient LED System - ATtiny85 + LDR + Mic - Circular PCB

I designed this round Diya board with 3.3V coin cell, ATtiny85, light and sound sensors in KiCad

My schematic - I divided into 5 units: Battery, ATtiny85 MCU, Light sensing, Light, Sound sensing

My PCB layout - Circular with BT1 3.3V Cell, R1/R3/R4 5.6k, D1, MK1, U1, SW2 - My actual design

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What I Made

I made a circular Diya LED board that runs on a 3.3V coin cell (BT1). It has both light sensing (LDR) and sound sensing (microphone) and a yellow LED, all controlled by my ATtiny85V.

I wanted to make a Diya that:

• Turns on automatically when dark (like real Diya at night)
• Saves battery when bright
• Maybe responds to clap sound too

So I added both LDR and mic!

My Schematic - 5 Units (What I Designed)

I divided my schematic into 5 units in KiCad (you can see in my Schmeatic-.png):

1. My Battery Unit

• BT1 3.3V Cell - I used a coin cell holder for CR2032 battery - Main power, portable, no USB needed
• SW2 SW_SPDT - I added a SPDT slide switch for power on/off

2. My Microcontroller Unit - ATtiny85

• U1 ATtiny85V-10P - I chose ATtiny85V low voltage version because it works on 1.8V-5.5V, perfect for my 3.3V coin cell
  • Pin 8 VCC → I connected to +3.3V
  • Pin 4 GND → GND
  • Pin 6 PB1 → I connected to my LED (D1)
  • Pin 7 PB2 → I connected to my LDR sensor (LDR node)
  • Pin 2 PB3 → I connected to my Mic sensor (MIC node)

3. My Light Sensing Unit

• R1 R - Fixed resistor to +3.3V
• R2 LDR07 - LDR to GND - Changes resistance based on light
• LDR node - Between R1 and R2 → To ATtiny85 PB2
• How I made it: +3.3V → R1 → LDR node → R2 LDR → GND - Voltage divider. Dark = High resistance → HIGH voltage, Bright = Low → LOW

4. My Light Unit

• D1 5mm Yellow LED - I chose yellow for warm Diya glow
• R3 R - Resistor to GND - Limits current
• LED node → ATtiny85 PB1 - My code controls LED on/off

5. My Sound Sensing Unit

• R4 5.6k - Pull-up resistor from +3.3V to MIC node - Value 5.6k visible in my PCB!
• MK1 Microphone_Condenser - Electret mic to GND - Picks up clap/sound
• MIC node - Between R4 and MK1 → To ATtiny85 PB3

My Board Features (From My Image)

• Circular PCB - Diya shape
• BT1 3.3V Cell - Coin cell holder
• R1, R3, R4 5.6k - Resistors
• D1 - LED
• MK1 - Microphone / LDR sensor
• U1 - 8-pin IC (ATtiny85)
• SW2 - Push button
• SW_SPDT - Slide switch
• Low power - Runs on coin cell

📁 My Files

kicad-ambient-led-system/
├── README.md (this file)
├── hardware/
│   ├── LayoutPcb.png (My circular PCB image)
│   └── Schmeatic-.png (My schematic - 5 units)
└── LICENSE

I already uploaded LayoutPcb.png and Schmeatic-.png

How My Board Works

Power: BT1 3.3V Cell → SW2 switch → Powers ATtiny85, sensors, LED

Light Sensing: +3.3V → R1 → LDR node → R2 LDR07 → GND → LDR node → ATtiny85 PB2

Sound Sensing: +3.3V → R4 5.6k → MIC node → MK1 Mic → GND → MIC node → ATtiny85 PB3

LED: +3.3V → D1 Yellow LED → R3 → GND, controlled by ATtiny85 PB1

My Code Plan:
- Read PB2 LDR: Dark → LED on, Bright → LED off (save battery)
- Read PB3 Mic: Clap → Toggle LED

My example code for ATtiny85:

const int ledPin = 1; // PB1 - My D1 LED
const int ldrPin = A1; // PB2 - My LDR
const int micPin = A3; // PB3 - My Mic

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

void loop() {
  int ldrValue = analogRead(ldrPin);
  int micValue = analogRead(micPin);

  if (ldrValue > 500) {
    digitalWrite(ledPin, HIGH); // Dark → LED on
  } else {
    digitalWrite(ledPin, LOW); // Bright → LED off
  }

  if (micValue > 700) {
    digitalWrite(ledPin, !digitalRead(ledPin)); // Clap → Toggle
    delay(500);
  }
  delay(100);
}

My Photos

How to View My Design

1. Install KiCad 7.0: https://kicad.org/download/
2. Clone:

git clone https://github.com/jay-waghmare/kicad-ambient-led-system.git

3. Open in KiCad

My Roadmap

• I designed KiCad schematic - 5 units - Done!
• I designed PCB - Circular - Done!
• I uploaded schematic and PCB images - Done!
• I will add KiCad project files
• I will write ATtiny85 code
• I will fabricate PCB and test

What I Learned

• Circular Edge.Cuts for Diya shape
• BT1 coin cell holder
• Low power with 5.6k resistor
• ATtiny85V for coin cell
• Voltage divider with LDR
• Pull-up with mic

About Me

I am Jay Waghmare - I design round PCB Diya with ATtiny85 + LDR + Mic

• My GitHub: @jay-waghmare

If you like my round Diya PCB, please ⭐ star!

License

MIT License

My circular Diya PCB with BT1 3.3V Cell + U1 ATtiny85V + R2 LDR07 + D1 Yellow LED + R4 5.6k + MK1 mic - I designed from scratch in KiCad - Based on my actual schematic Schmeatic-.png and PCB LayoutPcb.png