I have a project that opens a window blind in the day and closes it at night. It worked great for a week or two until we had a power outage. That night the blind tried to open, and in the morning it tried to close. Seems like the rotation reversed. I dealt with it by reversing two of the stepper wires. But since then it seems to reverse direction intermittently unexpectedly. I don't mean it reverses while turning, but that at dusk sometimes it tries to open when it should close and vice versa.
It uses a Trinket 5V, an SN754410E H-bridge, and a NEMA 17 motor (pretty sure but no markings).
// WARNING! If the motor is too strong this program can damage your blind.
// Customize these params according to your board. Make sure your PHOTO_PIN supports analog in and that
// you use the analog pin number, not the board pin number.
#define PHOTO_PIN 1 // Analog pin 1 = PB2 on the trinket
#define A1_PIN 1
#define A2_PIN 0
#define B1_PIN 3
#define B2_PIN 4
#define ANALOG_BITS 10
#define ANALOG_MAX ((1 << ANALOG_BITS) - 1)
// You may need to reduce AVG_HEAD if the motor starts at the wrong time of day
#define AVG_HEAD 0.5 // Weight of the latest sample
#define AVG_TAIL (1.0 - AVG_HEAD)
// Reduce DAYLIGHT for day to start earlier / end later. Increase DAYLIGHT_MARGIN if the blind reverses
// immediately after it opens / closes.
#define DAYLIGHT 0.5
#define DAYLIGHT_MARGIN 0.02
// Customize these params according to your motor.
#define STEPS 200
#define RPM 100
// Customize this param according to your blind.
#define TURNS -5 // Turns at sunset
Stepper stepper = Stepper(STEPS, A1_PIN, A2_PIN, B1_PIN, B2_PIN);
bool isOpen = false; // Make sure your blind is in this position when booting.
float avgLight = isOpen ? 1.0 : 0.0;
// Return the lightness value calculated with exponential moving average.
float sample() {
float floatRead = ((float) analogRead(PHOTO_PIN)) / ANALOG_MAX;
avgLight = (avgLight * AVG_TAIL) + (floatRead * AVG_HEAD);
return avgLight;
}
void setup() {
// These may or may not be strictly necessary
pinMode(A1_PIN, OUTPUT);
pinMode(A2_PIN, OUTPUT);
pinMode(B1_PIN, OUTPUT);
pinMode(B2_PIN, OUTPUT);
pinMode(PHOTO_PIN, INPUT); // or INPUT_PULLUP if you do not have a pullup resistor in place
stepper.setSpeed(RPM);
delay(1);
}
void turn(int rotations) {
stepper.step(rotations * STEPS);
// Turn off the current because the stepper doesn't need to hold in place.
digitalWrite(A1_PIN, 0);
digitalWrite(A2_PIN, 0);
digitalWrite(B1_PIN, 0);
digitalWrite(B2_PIN, 0);
}
void loop() {
float s = sample();
if (isOpen && s < DAYLIGHT - DAYLIGHT_MARGIN) { // Sunset happens
turn(TURNS); // Assuming positive rotations to close
isOpen = false;
} else if (!isOpen && s > DAYLIGHT + DAYLIGHT_MARGIN) { // Sunrise happens
turn(-TURNS); // Assuming negative rotation to open
isOpen = true;
}
delay(1);
