Twilight Mk2

The picture shows an updated version of Twilight driving a 3W LED inside a salt crystal. The new circuit:

• does away with the LEDs, using the controlled light itself as an indicator,
• ditches the variable resistor, using a long-press on the switch to indicate the light-level at which to switch on,
• stores this light-level in EEPROM to preserve it across power cycles
• uses an ATtiny85 for a smaller footprint

When switched on for the first time, the light is flashed quickly four times. When the environment reaches the desired level of twilight, the user presses the switch for two seconds to indicate this light level is to be stored. The light is then flashed slowly twice.

A circuit diagram and sketch (for Arduino 1.0) are shown below.

	#include <EEPROM.h>
	#define MOTION 1
	#define SWITCH 0
	#define LIGHT 2
	#define LDR 3
	#define HZ 4
	#define SAMPLES (15*HZ)
	#define ON_DELAY (15*60*HZ)
	#define OFF_DELAY (15*HZ)
	#define THRESHOLD 0
	boolean off = true;
	int onCount = 0, offCount = 0;
	int samples[SAMPLES], pos, smoothed;
	long total, press_time;
	boolean depressed;
	int threshold;
	inline int readLight() {
	return analogRead(LDR);
	}
	int sampleLight() {
	int curr = readLight();
	total += curr - samples[pos];
	samples[pos++] = curr;
	if (pos == SAMPLES) pos = 0;
	smoothed = (int)(total / SAMPLES);
	return smoothed;
	}
	#define SLOW 250
	#define FAST 125
	void blink(int d) {
	int n = 500 / d;
	for (int i = 0; i < n; i++) {
	digitalWrite(LIGHT, HIGH);
	delay(d);
	digitalWrite(LIGHT, LOW);
	delay(d);
	}
	}
	void setup() {
	pinMode(MOTION, INPUT);
	pinMode(SWITCH, INPUT);
	digitalWrite(SWITCH, HIGH); // activate pull-up
	pinMode(LIGHT, OUTPUT);
	smoothed = readLight();
	for (int i = 0; i < SAMPLES; i++) {
	samples[i] = smoothed;
	total += smoothed;
	}
	int t = EEPROM.read(THRESHOLD);
	if (t == 0xff)
	blink(FAST);
	else {
	blink(SLOW);
	threshold = 4 * t;
	}
	}
	inline long manual() {
	boolean d = (digitalRead(SWITCH) == LOW);
	if (depressed && !d) {
	depressed = false;
	return millis() - press_time;
	}
	if (!depressed && d) {
	depressed = true;
	press_time = millis();
	}
	return 0;
	}
	inline boolean isDark() {
	return smoothed >= threshold;
	}
	void turnOn() {
	if (off) {
	digitalWrite(LIGHT, HIGH);
	off = false;
	}
	}
	void turnOff() {
	if (!off) {
	digitalWrite(LIGHT, LOW);
	off = true;
	}
	}
	inline boolean movement() {
	return digitalRead(MOTION) == HIGH;
	}
	void loop() {
	int s = sampleLight();
	long d = manual();
	if (d > 0) {
	if (d > 1000) {
	threshold = s;
	EEPROM.write(THRESHOLD, (uint8_t)(s / 4));
	blink(SLOW);
	}
	if (off) {
	turnOn();
	onCount = ON_DELAY;
	} else {
	turnOff();
	offCount = OFF_DELAY;
	}
	} else if (movement()) {
	onCount = ON_DELAY;
	if (offCount == 0 && isDark())
	turnOn();
	} else if (onCount == 0)
	turnOff();
	delay(1000 / HZ);
	if (offCount > 0) offCount--;
	if (onCount > 0) onCount--;
	}

view raw twilight2.ino hosted with ❤ by GitHub