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[vince]

I would like to know more about battery powered devices. I hear that they can run for years without replacing batteries. What about battery powered thermostats??

[Protocol]

Hello,

There seems to be several models popping up including battery powered motion detectors and such. Is this the right way to go? Most people don't even change their smoke detector batteries...I wonder how many will think of checking the batteries in the tstat, motion detector etc?

I can see a lot of service calls with this type of equipment due to dead batteries. What do you think?


Protocol

[emmsys]

Hi guys,

Since you're posting in the wireless section, I'm guessing you mean battery-powered wireless devices?  Power consumption, energy savings, and "going green" are all the rave now. A lot of people equate "being battery powered" with energy and cost savings. I'm not sure it's as clear cut as that, but the recent trend is definitely moving towards more battery-powered wireless devices. The cost savings are obvious (no need to pull wire) but there's also the flexibility of putting this wireless device anywhere you want to. There are battery powered thermostats, light switches etc. out there now running on ZigBee. It's interesting how the technology works. These devices are not actually "off" in the sense that they do not draw any power at all. Their microcontrollers are actually put in an ultra low power (or sleep) state. In this sleep state, the microcontroller will only revert to full-on mode when certain actions occur (like pressing a key on a remote, flicking a light switch or even waking up at fixed intervals). Typically a sleeping microcontroller running on a battery would result in the battery lasting its entire shelf life. Unfortunately it doesn't always translate into that in the real world. With wireless devices, it's possible to draw over 35mA to transmit and receive. The more work you do between sleep cycles the more energy you draw. That's why cellphones only have a talk time of a few hours but standby times in the order of days. See the difference in energy consumption?

Like Protocol said, I too think battery-powered devices aren't the solution to ALL our problems. Imagine a hotel having to replace 1-2 button-cell batteries for all of it's 150-300 rooms every few years? I wouldn't want to be the tech that has to do it! Granted, these products will likely have low-battery alarms anyway so it wouldn't be a huge mess but it's still effort every few years.

emmsys