Simple Digital On Off Cycler V1-A30m in Beta

On my Saturday I made this device which is the first actually useful thing I made with my Arduino (aside from a tiny programmer and a energylogger which haven't really been used).

It is a VERY simple thing that just switches some 220V AC power on and off on a 30 minute cycle. In beta testing I'm just turning a light on and off:

The main reason I made this is that the Vaporizer in my son's room empties halfway through the night on it's minimum setting, so with this I can switch it on on a half-hourly cycle so that it will last the night.

Let me know if you want one, I'll sell these if there is interest :)

It even has 2 LED's for debugging. The green one is on while it gives power out. The yellow one blinks 100 times each cycle (so if the cycle is 30 minutes, it is on for 9 seconds and then off for 9 seconds and so on).

I tested and measured over and over again to make sure it is safe, but I'm just an amateur electronics guy hacking away, so I should get this reviewed to make sure I don't burn my house down when leaving it on over night.

To my wife's dismay I made quite a mess, but I cleaned up nicely afterwards :)

When I did the tiny programmer I went straight from the breadboard to veroboard, this time I wrote down the design and I think in future I should really try to draw and lay it out on DipTrace first. This is open hardware, so here is the design and code so far:

==

#define BLINK_PIN 13
#define RELAY_PIN 12
#define MULTIPLIER 100

int cycleSeconds = 30*60;
int sleepMS = round(cycleSeconds * 1000 / MULTIPLIER / 2);
int counter = 0;
int blinkLevel = LOW;
int relayLevel = HIGH;

void setup() {                
  pinMode(BLINK_PIN, OUTPUT);     
  pinMode(RELAY_PIN, OUTPUT);     
  digitalWrite(RELAY_PIN, relayLevel); // start on
}

void loop() {
  if (blinkLevel == LOW)  {
    blinkLevel = HIGH;
    counter += 1;
  } else {
    blinkLevel = LOW;
  }
  digitalWrite(BLINK_PIN, blinkLevel);    
  
  if (counter >= MULTIPLIER) {
    counter = 0;
    if (relayLevel == LOW)  {
      relayLevel = HIGH;
    } else {
      relayLevel = LOW;
    }
    digitalWrite(RELAY_PIN, relayLevel);    
  }
  
  delay(sleepMS);       
}
==

For next versions I'll use an ATTINY85 in stead of the arduino, I can add some knobs to control the cycle times and maybe rather build it into a multi adaptor.