I'm working on a project where power requirements is a big issue, and looking into saving power by entering sleep mode.
I'll probably use the arduino pro mini 3.3v for maximum power savings.
The problem is the wake up call, getting the arduino into sleep is no problem, but I need to wake up the aurdino about 2 times in 24 hours to do some work via an interrupt. And I cannot depend on daylight source.
Timing of the wakeup is not so important, only in a 24 hour timeline it should have triggered about 2 times. I'm thinking about a resistor/capacitor/transistor trigger on the interrupt line, but I'm not sure what values to use to minimize idle power usage for the wake up circuit on a 12 hour cycle, and avoiding usage of big electrolytes. Any ideas or pointers to help me with this?
btw, a Big Thank You, to the people and community making the arduino hw/sw. This is fun stuff!!
You're not going to get anywhere with an RC timer for this.
If you need really really low power, use an external RTC with an alarm output. The DS1307 is readily available, draws a tiny amount of power, and is be rather well supported on this forum.
If thats not an option, it can be done with no xtra hardware, but a bit more current consumption.
Timer1 can be set to generate an interrupt every second. The interrupt will wake your Arduino.
In your interrupt routine, you increment a counter, looking for it to reach 43,200 (43,200 seconds is a half day).
Until then , your interrupt routine just puts the Arduino back to sleep.
When the counter reaches 4300, clear the counter, do your work, and then go back to sleep.
I had similar requirement about power, but in this forum people say that it is not possible to get up the arduino by the use of ds1307 since it not have alarms.
But i received some recomendations in this forum to use DS1337 RTC since it is able to trigger to different alarms
If somebody knows how to trigger alarms by DS1307 it could be a great new for those of us using this component!
DS1305 then? "Two programmable time-of-day alarms are provided by the DS1305. Each alarm can generate an interrupt on a programmable combination of seconds, minutes, hours, and day."
This could probably save my day. I dont need such accurancy, actually. I could need more diversion on the trigger. Given a set of lot of devices, they should not trigger on the same time, but I can program my way out of that. I would have hoped for a simpler sollution, but this is a good direction to examine! thanx for the suggestions so far!