So I have some basic experience with coding and need some help. My project is to turn lights on and off with the light exposure. I have the basic code to drive the lights already done. I am using a arduino uno, a simple photon resistor and an LED. The schematic is shown below as well as the code.
<
const int PHOTON = A3;
const int LED = 5;
const float VCC = 4.98;
const float R_DIV = 4684;
const float DARK_MIN = 8000;
if (lightR >= DARK_MIN)
digitalWrite(LED, HIGH);
else
digitalWrite(LED, LOW);
}
}
My project board has an LED attached to digital pin 5 already. I don't want the system to turn the lights off though if they are exposed quickly to a flashlight for a few seconds. I know that millis() would be how to use it but dont know how to implement it into my code already. I want the system to wait 30 seconds and if a light is still on the photon sensor, turn the lights off. I appreciate any help.
As is usually the case with me when looking at problems like this, I'd suggest a finite state machine. Here's some "pseudocode" you can have a look at:
void loop()
{
static uint32_t
timeLDR;
static uint8_t
stateLDR = ST_IDLE;
uint32_t timeNow = millis();
switch( stateLDR )
{
case ST_IDLE:
//if LDR shows some level of brightness...
if( LDR reads at or above turn-off threshold )
{
//get the time now and move to time the exposure
timeLDR = timeNow;
state = ST_TIME_EXPOSURE;
}//if
break;
case ST_TIME_EXPOSURE:
//if the LDR shows below the threshold, go back to idle
if( LDR reads below turn-off threshold )
stateLDR = ST_IDLE;
else if( timeNow - timeLDR >= 30000ul ) //time 30-sec or more?
{
//if exposure has been there for 30-sec turn off lights
turn lights off
timeLDR = timeNow;
//wait until it's "dark" again before turning lights on and going back to idle
stateLDR = ST_WAIT_DARK;
}//if
break;
case ST_WAIT_DARK:
//wait for LDR to show "dark" for more than 30-sec
if( LDR reads at or above dark threshold ) //if LDR shows brightness, reset the timer
timeLDR = timeNow;
else
{
//still dark; been dark for 30-sec?
if( timeNow - timeLDR >=30000ul )
{
//yes; turn on lights and return to idle state
turn lights on
stateLDR = ST_IDLE;
}//if
}
break;
}//switch
}//loop
You won't need everything shown if all that's needed is a timer controlled light but this timer counter state change toggle FSM tutorial illustrates the concepts to control your lights.
