Remote sensor, advice needed

Greetings,
  I am planning a project that involves a remote sensor (eg, temp) that
sits idle but has to send an alert when the trigger goes off.  The
requirements are:

- Low power: has to be able to remain idle for about 1 week if needed.
- Has to transmit over wireless from across town (Atlanta, 30min drive
or so).
- In the fufture, has to be able to send an image from a camera. BW is
fine 640x480 is also fine.
- Form factor has to be as small as possibe, and does not have to be
weatherproof since it will be inside.

I have been looking at gprs or something similar.  I do not have enough
experience with these systems although I have built many
electronic/FPGA projects in the past.

Does anyone have any insights or advice about this?  Any kind of info
would be helpful, eg, which microcontroller would you use, is gprs the
way to go in the US or is there another RF solution?  Subscriber fees,
if needed, are not a big issue if it works reliably and well.  The
reason I say gprs is because I do not know how far does RF reach.

Thank you for your time and help.

A

amerdsp wrote:
> Greetings,
>   I am planning a project that involves a remote sensor (eg, temp) that
> sits idle but has to send an alert when the trigger goes off.  The
> requirements are:
> 
> - Low power: has to be able to remain idle for about 1 week if needed.
> - Has to transmit over wireless from across town (Atlanta, 30min drive
> or so).
> - In the fufture, has to be able to send an image from a camera. BW is
> fine 640x480 is also fine.
> - Form factor has to be as small as possibe, and does not have to be
> weatherproof since it will be inside.
> 
> I have been looking at gprs or something similar.  I do not have enough
> experience with these systems although I have built many
> electronic/FPGA projects in the past.
> 
> Does anyone have any insights or advice about this?  Any kind of info
> would be helpful, eg, which microcontroller would you use, is gprs the
> way to go in the US or is there another RF solution?  Subscriber fees,
> if needed, are not a big issue if it works reliably and well.  The
> reason I say gprs is because I do not know how far does RF reach.
> 
> Thank you for your time and help.
> 
> A
> 
Which country will this device be in at deployment ?

If its the USA, there are a few cell phone modems that can do this job.
http://www.sparkfun.com/commerce/categories.php?cPath=66_68

If you want to do this on the cheap, using an off the self cell phone, 
there is no interface available on US cell phones. Unless you want to 
use a laptop as your embedded system.

Good Luck

donald

amerdsp wrote:
> Greetings,
>   I am planning a project that involves a remote sensor (eg, temp) that
> sits idle but has to send an alert when the trigger goes off.

Certainly it is possible to make a radio that transmits reliably over
30km, but as you guessed, the FCC won't allow it without a permit.

If it is really near Atlanta, the phone company should be able to run a
line to the location.  Then you could get rid of both power problem and
communications problem at once.

-Le Chaud Lapin-

Unfortunately, I am unable to connect a land line to the location since
it changes every so often.  The unit has to be portable as well, so low
power is also key.

I am starting to get convinced that cellphone data is the only way to
go with this.

What small power supplies do people use on par with a 9V battery, size
and performance?  I mention 9V because its the only one I know.  All my
previous projects had a bench power supply.  This is the first time I
have to consider the limited amount of power.  Do you think a  9V would
be enough for the cell phone module, microcontroller for about 1 week?
I understand that during inactivity, all will be in standby low power
mode, unless a trigger happens.

Thank you all for the good information.

A

amerdsp wrote:
> Unfortunately, I am unable to connect a land line to the location since
> it changes every so often.  The unit has to be portable as well, so low
> power is also key.
> 
> I am starting to get convinced that cellphone data is the only way to
> go with this.
> 
> What small power supplies do people use on par with a 9V battery, size
> and performance?  I mention 9V because its the only one I know.  All my

Don't get out much, eh .  ;-)


> previous projects had a bench power supply.  This is the first time I
> have to consider the limited amount of power.  Do you think a  9V would
> be enough for the cell phone module, microcontroller for about 1 week?

Which module are you thinking of using ???

> I understand that during inactivity, all will be in standby low power
> mode, unless a trigger happens.
> 
> Thank you all for the good information.
> 
> A
> 

The GM862-PCS Key features:

     * 17mA average stand-by, 3.5mA in low-power mode
     * 250mA average operating current
     * Data, Voice, SMS, and Fax
     * Data speeds up to 57.6kbps
     * Supply voltage : 3.4-4.2V
     * CMOS Camera Capable
     * MMCX Antenna Connector
     * Extensive datasheets and forum support


Supply is 3.4 to 4.2 volts with an operating current of 250 ma.

I should work. but as always, try it out a few times for deploying in 
the field.


donald

PS: I have not used this module. Like any other design, read the data 
sheets and evaluate the possibilities.
Then be ready to be wrong.