Xbee standalone sensor unit

[joanba]

Hi,

I'm designing an standalone sensor unit based on an XBee circuit. I want to know which components I need to include in order to support the following features:

- Solar powered
- Waterproof ( temperature range: -20ºC to 45ºC ), maybe some box required.
- Low cost is desirable
- Some space will be required for sensors ( connected to XBee inputs ) and probably some electronic components.

I'm considering a combination of an XBee board wiht a LiPoly charger with a solar pannel but I don't know if there is any kit already available. Can you help me, please ?

Regards,
Joan

[adafruit_support_bill]

We don't have a kit that includes all that. But we do have a selection of components that should work for your project.

Solar panel and battery size will depend on the expected current demands and solar conditions. The panel ratings are for direct sunlight. Output will be considerably less at dawn, dusk or cloudy conditions.
You will want to use the Solar version of the LiPoly charger. http://www.adafruit.com/products/390 The tutorial explains the solar-specific aspects of the charger design.
For enclosures, we carry several sizes of waterproof Otter Boxes https://www.adafruit.com/index.php?main ... ch&q=otter
as well as weatherproof enclosures in two sizes: https://www.adafruit.com/index.php?main ... +enclosure

[joanba]

Hi,

Just a final question about the 390 charger: Does it will power an XBee adapter that has an input Vcc of 5Volts ( regulator is KB33 ) ? What adapter do you recommend ?

Regards,
Joan

[adafruit_support_bill]

That is a very low-dropout regulator and should be able to power the XBee from battery voltages down to about 3.5v. A fully charged LiPo is 4.2v and will supply about 3.7v for most of its useful discharge cycle.

[joanba]

Hi,

And if you have to power an XBee with the 390 lipoly charger, what do you recommend ?

Regards,
Joan

[adafruit_support_bill]

The "Load" output from the charger will be the same as the battery charge level. It should be sufficient to drive the adapter.

[prussia]

Hi Joanba,
I'd like to join in as i'm interested in creating a similar project. I started by hacking a solar plant light (see below) for power.

My use case: Creating Xbee zones that monitor sensor data from the front yard, back yard and indoor plants and send it back to a Pi. Each zone would have multiple hygrometers, a temp sensor, and a light sensor. Eventually I'd like for the zones to water plants as needed but i haven't figured out that part yet.

Sensors in Mind:
1. Hygrometer /Moisture Sensor- analog
2. TMP36 analog temp sensor from Adafruit
3. Light sensors and solar gear I hacked from a solar garden light for now but I think Adafruits solution is much more reliable.
4.MCP23017 ADC chip (not a sensor) communicating through I2c back to the mother Pi

Questions:
1. How would you send data back to the Pi? Can you use the ADC chip listed above communicating with the I2C protocol to expand the number of analog sensor inputs in each zone ? I haven't found any examples of connecting Xbee devices to analog sensors that doesn't involve plugging the sensors directly onto the xbee analog input.
2. What is the best way of implementing power saving mode. It seems the Xbee can wake up at pre-determined times, take readings, transmit them and go back to sleep. Can you use wake from sleep there?

I apologize if this information is better in it's own post and would gladly repost if you would like.

Thanks

[joanba]

Hi,

First of all excuse this late answer. I will answer your questions:

1. How would you send data back to the Pi? I don't use PI, I'm using Arduino with a wireless shield that allows to connect and XBee and send/receive data using a serial port. Is explained in a lot of sources, is really easy.

2. What is the best way of implementing power saving mode. It seems the Xbee can wake up at pre-determined times, take readings, transmit them and go back to sleep. Can you use wake from sleep there? Yes, of course. I sleep XBee all the time, and I wake it up during 10 seconds every hour, in this way I have enough time to have 5 consistent reads of my sensor. The problem with sleep mode is that when configured the XBee is dead, so I propose to install a reset button in order to wake it up for test purpouses.

Regards,
Joan