[SOLVED] Timer IC that doesn't reset count because of power down and remembers last state

Hello,

I'm looking for a timer/RTC that will count how long the system power was up in total and will toggle a pin after a specific time that will be configured in advance.
Does a timer that "remembers" exists?

For example, on the first time that the system is powered up for 2 hours, after this it's down, and powered up for 1 more hour, so in total the timer will be already 3 hours, etc.
After 500 hours (for example) I'd like to toggle a pin that will notify this.

The time resolution can be even hours, but I don't want to use a microcontroller (except for initial values configuration) or a battery (or supercap because I don't know for how long it will be down).

My main purpose is small size and less components, Power consumption is not an issue.


Thanks

You are asking for a clock that keeps time and can toggle a pin without any power source at all. It doesn't exist.
The best you will manage is a system that records start-up time in NVRAM and rechecks it each time the power is applied.

Incidentally, a small super-cap (0.47F for example) will keep an RTC IC running for several months. I have used DS1302 RTCs with built in charger to keep a supercap topped up and it has still kept time 3 months after the power was removed.

Brian.

Hi,

what resolution do you need and what accuracy do you need? (Please values with units.)

Generally, every battery powered microcontroller should work. One input to detect the presence of system power, one output pin as desired.

Klaus

DS1682 Total-Elapsed-Time Recorder with Alarm might serve your purpose. https://www.maximintegrated.com/en/products/analog/real-time-clocks/DS1682.html

KlausST said:

Hi,

what resolution do you need and what accuracy do you need? (Please values with units.)

Generally, every battery powered microcontroller should work. One input to detect the presence of system power, one output pin as desired.

Klaus

Click to expand...

The accuracy is not very important to me, and a resolution of hours is also good (of course that minutes or seconds is even better).

betwixt said:

You are asking for a clock that keeps time and can toggle a pin without any power source at all. It doesn't exist.
The best you will manage is a system that records start-up time in NVRAM and rechecks it each time the power is applied.

Incidentally, a small super-cap (0.47F for example) will keep an RTC IC running for several months. I have used DS1302 RTCs with built in charger to keep a supercap topped up and it has still kept time 3 months after the power was removed.

Brian.

Click to expand...

Interesting

FvM said:

DS1682 Total-Elapsed-Time Recorder with Alarm might serve your purpose. https://www.maximintegrated.com/en/products/analog/real-time-clocks/DS1682.html

Click to expand...

Looks very close to what I need.


Thanks you all for your answers, it gave me good hints for what I need to look for!