Keep Track of minutes and seconds Arduino

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hi all, doing project in making lock. lock unlocks via keypad, , want have different things going on once unlocked. give user option press d key on keypad re-lock it, if not re-locked in 5 minutes set off alarm (piezo speaker). cannot delay, because there not enough time user react , press d key. how put action on timer, timer can counting without stopping entire code?

google time library!


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