Issue 140 March 2002
Spy-Size Event Logger

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Logging capabilities aside, the device can be programmed to trigger the INT pin every second or upon a seconds match, a seconds/minutes match, a seconds/minutes/hours match, or a seconds/minutes/hours/day-of-the-week (DOW) match. Accessing any alarm register resets the alarm output. This mode allows your circuit to sleep for up to a week at a time. That’s quite the low-current alarm!

I find this device extremely flexible and offer kudos to Dallas and Maxim. You can count on them to produce unique devices covering a wide range of applications. There are a couple of other new logging devices you may wish to research at the companies’ web sites, namely, the DS1615 and DS1616. Internal temperature sensors and ADC additions may satisfy more complex requirements.

In any event, I’ll be taking this project over to my well’s water pump to give me an indication of pump cycle times over the course of a week. I can use Trigger on Rising and Falling Edges mode to capture the on and off cycles of the pump. Note that the logger does not log on or off status, but I’ll be able to determine which is which because an event will occur at each transition between on and off. Additionally, the off times should be considerably longer than the on times, especially during nighttime hours. I wonder if I can monitor the gas pedal in my car to truly determine the best driving route?