Counting miliseconds between ON and OFF

[sayzer]

Ok, here is one concept.

You have an advantage here, ADC reading, that you can actually measure the voltage; it does not have to go off as you can continuously check the voltage level.

Since you are using a battery, power-off concept may not be a good (or let say precise) solution for you. But if you had a non battery operation with this circuit, this is the way to go.

Thus, reading (monitoring) the battery voltage at AN0 in your case is much more accurate.


Try and see....


<img src="http://img6.picsplace.to/img6/23/poweroff.gif" alt="Image Hosting by PicsPlace.to" >



Edit: I will post another circuit to read the voltage level with AN0.
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[peu]

My app is always battery powered, that diode makes sense I'm keeping an eye on the other circuit. Thanks!

[sayzer]

I was thinking about measuring the battery with ADC but then I realized that Vref will be Battery V+ and the ADC will be tied to V+ also.

As the battery goes down, the ADC Vref will also go down in parallel and the result will never change in theory. Even a resistor tied from ADC pin to either Gnd or V+ will also be perfectly proportional to battery V+ when it is going down. Thus ADC will not see the difference, I think.


This is just possibility came to my mind but I am sure someone already has done something similar and is experienced with this.

Am I right on this or there is another way to do it?


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[peu]

Hi Sayzer, I was thinking on using BOD but the fact that it resets the uC when its triggered put the idea to rest.

I know it can be done, because I saw others doing it...

Pablo