XBee, PIR Motion detector questions

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XBee, PIR Motion detector questions

Postby Digit » Sun Oct 11, 2009 8:57 pm

I've got [url="http://www.adafruit.com/index.php?main_page=product_info&cPath=35&products_id=189"]this[/url] Motion sensor connected to an XBee.

This XBee is plugged into a [url="http://www.sparkfun.com/commerce/product_info.php?products_id=9132"]XBee Explorer Regulated[/url].
This Explorer takes care of supplying the XBee the required 3.3V.
Current setup (XBee, Explorer, Motion sensor) uses 40 mA.

In my first setup i used 4 x AA batteries and a LM7805 voltage regulator to provide 5V to the motion sensor and Explorer.
However, after around 16 hours the output voltage of the 4 AA batteries started to reach 5.5V and i think the LM7805 becomes unstable at that point, cause i see the XBee sending motion events even when there's no motion. Now i know a LM7805 needs more then 5.5V...

My questions are:

- Is using a 9V battery a better idea? it has much less mAh (580 vs 2850) then AA which will decrease time to switch batteries.
- Wouldnt it be better to get rid of the Explorer regulated, which is only needed for the 5V > 3.3V voltage regulation. This will only add more loss, right?

So actually i would need a voltage regulator that can provide me both 5V and 3.3V with minimal losses.
How can i do that? What's the best way?

Elektro gurus, your advice please :-)
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XBee, PIR Motion detector questions

Postby RDNZL » Mon Oct 12, 2009 7:45 am

Cannot advice on the best regulator, but I think the 7805 series are not very efficient.
Can those Xbee modules be put into sleep mode too?
Thats also an important energy saver, look here for more info (for JeeNodes) not exactly matching your setup, but useful info I think.

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XBee, PIR Motion detector questions

Postby Post-IT » Mon Oct 12, 2009 9:21 am

Found this note while I was browsing for more ZigBee reading, might help you out. There are 2 modes: Sleep (Cyclic) and Hybernate.


And some more discussion on the Sleep mode here:
and here:
http://www.digi.com/support/kbase/kbase ... jsp?kb=193

Hope this helps you in the right direction.

I've been thinking about buying the Zigbee PIR in the Alertme kit (priced at 25 GBP): http://www.alertme.com/smart-energy/sta ... n-the-box/
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XBee, PIR Motion detector questions

Postby Willem4ever » Mon Oct 12, 2009 11:25 am


I think it would be better to design your solution with components which run on 3 Volt and not to use any voltage regulator at all. Once I have my setup running (on 3 volts) I'll post the results.
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