LED on off

This logic can be used to time a little LED chain when there is only an on/off switch for the 3 AA batteries. The NPN transistor used is BC550 The 4.5V switch turns the unit on and off. The switch before the 15k simulates logic level signal from ATTiny85 (or other) output pin. R values may need to change to match the actual LED configuration. A sample Arduino sketch: // LEDtimer.ino // gah Dec. 02, 2023 // This is supposed to go into an ATTINY85 to make it an on off timer for LEDs // Remove all console communication first unsigned long t_now = 0L; // initial value unsigned long t_8h = 0L; unsigned long t_16h = 0L; // We could also have a second on_time in the morning if desired. int ledPIN = 13; void setup() { delay (3000); // security delay Serial.begin (9600); pinMode(ledPIN, OUTPUT); t_8h = 1000L * 60 * 60 * 8; // initial 8h numerical representation in msec t_16h = 1000L * 60 * 60 * 16; // initial 18h numerical representation in msec } void loop () { digitalWrite(ledPIN, HIGH); // turn power to the LEDs ON Serial.println ("LEDs are powered ON now\n"); Serial.print ("Elapsed time since start = "); Serial.println (t_now); Serial.print ("\tt_8h = "); Serial.print (t_8h); Serial.print ("\tt_16h = "); Serial.print (t_16h); while (t_now < t_8h) { t_now = millis(); } digitalWrite(ledPIN, LOW); // turn power to the LEDs OFF Serial.println ("LEDs are powered OFF now\n"); Serial.print ("Elapsed time since start = "); Serial.println (t_now); Serial.print ("\tt_8h = "); Serial.print (t_8h); Serial.print ("\tt_16h = "); Serial.print (t_16h); while (t_now < t_16h) { t_now = millis(); } // This concludes 1 full day (24 hrs) // incerementing t_8h and t_16h values now t_8h = t_8h + 1000L * 60 * 60 * 24; t_16h = t_16h + 1000L * 60 * 60 * 24; // then loop untill battery is empty or power switch is pressed // if overflow occurs during that time you have an excellent battery. }

published 2 years ago