How to randomly hold for 5-30 minutes?

[travderose]

I want an LED to blink once but at random intervals of time that are between 5 and 30 minutes long.

For example: LED blinks, wait 18 minutes, LED blinks, wait 29 minutes, LED blinks, wait 7 minutes, etc.

What would be the best way to write this sketch on an Arduino Uno?

Appreciate any help or advice you can offer!

[jremington]

unsigned long millis_between_blinks = 60UL*random(5,31)*1000;

random() - Arduino Reference

[anon57585045]

@travderose

What would be the best way to write this sketch on an Arduino Uno?

Fingers work really well. Just kidding. Have you tried the Blink sketch yet? You can modify it to do what you ask.

[xfpd]

@jremington

unsigned long millis_between_blinks = 60UL*random(5,31)*1000;

For a more random randomness, prefix the above line with the following line (copied from the link)...

  // if analog input pin 0 is unconnected, random analog
  // noise will cause the call to randomSeed() to generate
  // different seed numbers each time the sketch runs.
  // randomSeed() will then shuffle the random function.
  randomSeed(analogRead(0));

[jremington]

The randomSeed() function should be called only once in a program, since it merely defines the start point of the (fixed) pseudorandom sequence of numbers produced by random().

[travderose]

YES! this is great