Need help with Clock Controller and relay contact

Projects General Guidance
1

I've been asked to develop a small circuit that will allow me to provide a dry contact closure to another control device, based on time of day and day of week. For example, I need the dry contact to provide the connection between two wires (no voltage) at a used defined time of day, and day of week. The dry contact must stay in effect for a minimum of 3 minutes in order for the other controller to "see" the connection.

So here's a real life example of what the circuit would be asked to do:

Every "x" number of days, at "y" time of day, close the connection between two wires, and hold that connection for at least three minutes.

How the heck do I do this.....can you at least offer a suggestion? I'm not looking for anyone to do my work for me, just some helpful guidance to get this old fart moving in the right direction.

Thank you....
Jim

2

One of my favorites is this library:
http://playground.arduino.cc/Code/Time

It includes a "TimeAlarms" library that I think will do just what you want. Use an external real time clock (RTC) if your particular system clock is not accurate enough.

Alarms

The Alarm library is a companion to the Time library that makes it easy to
perform tasks at specific times or after specific intervals.

Tasks scheduled at a particular time of day are called Alarms,
tasks scheduled after an interval of time has elapsed are called Timers.
These tasks can be created to continuously repeat or to occur once only.

Here is how you create an alarm to trigger a task repeatedly at a particular time of day:
Alarm.alarmRepeat(8,30,0, MorningAlarm);
This would call the function MorningAlarm() at 8:30 am every day.

If you want the alarm to trigger only once you can use the alarmOnce method:
Alarm.alarmOnce(8,30,0, MorningAlarm);
This calls a MorningAlarm() function in a sketch once only (when the time is next 8:30am)

Alarms can be specified to trigger a task repeatedly at a particular day of week and time of day:
Alarm.alarmRepeat(dowMonday, 9,15,0, MondayMorningAlarm);
This would call the function WeeklyAlarm() at 9:15am every Monday.

If you want the alarm to trigger once only on a particular day and time you can do this:
Alarm.alarmOnce(dowMonday, 9,15,0, MondayMorningAlarm);
This would call the function MondayMorning() Alarm on the next Monday at 9:15am.

Timers trigger tasks that occur after a specified interval of time has passed.
The timer interval can be specified in seconds, or in hour, minutes and seconds.
Alarm.timerRepeat(15, Repeats); // timer task every 15 seconds
This calls the Repeats() function in your sketch every 15 seconds.

If you want a timer to trigger once only, you can use the timerOnce method:
Alarm.timerOnce(10, OnceOnly); // called once after 10 seconds
This calls the onceOnly() function in a sketch 10 seconds after the timer is created.

If you want to trigger once at a specified date and time you can use the trigger Once() method:
Alarm. triggerOnce(time_t value, explicitAlarm); // value specifies a date and time
(See the makeTime() method in the Time library to convert dates and times into time_t)

Your sketch should call the Alarm.delay() function instead of the Arduino delay() function when
using the Alarms library. The timeliness of triggers depends on sketch delays using this function.
Alarm.delay( period); // Similar to Arduino delay - pauses the program for the period (in milliseconds).