ATTINY85 TINY85 Micro USB Development Board – Small Automation Projects (Example: Night Light / Relay Control)

Overview

Compact ATTINY85 development board with Micro-USB programming and power. Small, low-power and perfect for embedded automation tasks. The example below demonstrates a typical small automation: an automatic night light that turns a relay on when ambient light is low, with a manual override button. The example is written for the Arduino environment (ATTiny cores) and is intentionally simple to adapt.

Key benefits

• Very small footprint, USB powered and programmer-friendly
• Supports I²C (software), ADC, PWM and GPIO
• Ideal for low-cost, low-power automation and gadget projects
• Ready for Arduino IDE with ATTiny cores (examples included)

Wiring (Night-Light / Relay Example)

Board pin mapping (common ATTiny85 boards):
  PB0 -> Arduino D0 / A0
  PB1 -> Arduino D1
  PB2 -> Arduino D2 / A2 (ADC)
  PB3 -> Arduino D3
  PB4 -> Arduino D4
  PB5 -> RESET (do not use for I/O)

Example wiring:
  LDR (voltage divider) -> A2 (PB2)
  Manual button (momentary) -> D0 (PB0) with INPUT_PULLUP
  Relay module IN -> D1 (PB1)  (use a relay module with proper transistor / optocoupler)
  VCC -> 5V (from Micro-USB)
  GND -> GND

Important:
  - Use a relay module rated for your load; isolate mains wiring and follow safety rules.
  - Many ATTiny boards run at 8MHz internal clock; set this in the Arduino board settings.

What this example does

The sketch reads an analog LDR value and switches a relay ON when ambient light falls below a configurable threshold. A manual button provides an override (toggle). Basic hysteresis prevents relay chatter near the threshold. This demonstrates a practical small automation task suitable for hallways, cupboards, garden lights, or equipment cabinets.

Code — Arduino (ATTiny85)

/*
  ATTINY85 Night Light + Manual Override
  - LDR (voltage divider) connected to A2 (PB2)
  - Manual button to PB0 (D0) using INPUT_PULLUP
  - Relay module IN to PB1 (D1)  (logic HIGH turns relay ON; invert if your module is active LOW)
  Notes:
  - Confirm pin mapping for your ATTiny85 board variant.
  - Compile with ATTiny85 core (e.g., SpenceKonde / AttinyCore) and set correct clock/source.
*/

const uint8_t PIN_LDR    = A2;    // PB2 (analog)
const uint8_t PIN_BUTTON = 0;     // PB0 (digital, INPUT_PULLUP)
const uint8_t PIN_RELAY  = 1;     // PB1 (digital output)

const int LIGHT_THRESHOLD = 450;  // 0..1023 - lower = darker
const int HYSTERESIS = 30;        // prevents chatter

bool relayState = false;
int lastLdr = 0;
unsigned long lastDebounce = 0;
const unsigned long BUTTON_DEBOUNCE_MS = 50;

void setup() {
  pinMode(PIN_RELAY, OUTPUT);
  digitalWrite(PIN_RELAY, LOW); // ensure relay off at boot (adjust if active LOW)
  pinMode(PIN_BUTTON, INPUT_PULLUP);
  analogReference(DEFAULT); // use default reference; some builds may differ
}

void toggleRelay() {
  relayState = !relayState;
  digitalWrite(PIN_RELAY, relayState ? HIGH : LOW);
}

void loop() {
  // Read LDR
  int ldr = analogRead(PIN_LDR);

  // Simple hysteresis logic
  if (!relayState && ldr < (LIGHT_THRESHOLD - HYSTERESIS)) {
    // it's dark -> turn ON
    relayState = true;
    digitalWrite(PIN_RELAY, HIGH);
  } else if (relayState && ldr > (LIGHT_THRESHOLD + HYSTERESIS)) {
    // it's bright -> turn OFF
    relayState = false;
    digitalWrite(PIN_RELAY, LOW);
  }

  // Button handling (debounced)
  int buttonRead = digitalRead(PIN_BUTTON);
  if (buttonRead == LOW) { // pressed (INPUT_PULLUP)
    if (millis() - lastDebounce > BUTTON_DEBOUNCE_MS) {
      toggleRelay();
      lastDebounce = millis();
      // simple delay to avoid multiple toggles; acceptable in tiny automation
      delay(200);
    }
  }

  // (Optional) small delay to reduce CPU usage
  delay(200);
}
  

Notes on programming & setup

• In Arduino IDE install an ATTiny core (e.g., AttinyCore) and select the correct board + clock (many boards run 8MHz internal).
• Upload using a USB-AVR programmer, or use the board’s Micro-USB if it exposes a bootloader compatible with your core.
• If your relay module is active-LOW invert the digitalWrite logic accordingly.
• For battery operation consider adding sleep/low-power code (libraries such as LowPower or using AVR sleep modes).

Possible Uses (small automation focus)

• Automatic night lights for hallways, cabinets or porches
• Simple timer-based or sensor-based relay control
• Door/window small actuator control (garage mini-projects)
• Low-cost environmental triggers (light, temperature via simple sensors)
• Appliance keep-alive or watchdog toggles for legacy devices
• Power-saving automation for battery devices (with sleep)
• Small educational automation kits and STEM projects

Package & title

• Package includes: 1 × ATTINY85 Micro USB Development Board

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