Hi Adam

Those are all very good ideas. Transmitting a few day's data is a nice 
twist. As for the lower frequencies, I have some experience with Linx 
tech's chips at 434Mhz. I can apply that experience. I have been 
thinking too much about bi-directional communication, and, I should 
think more laterally it seems.

You have given me lots to think about.

Thanks

Rolf



M. Adam Davis wrote:
> A few points:
>
> 1.  You're transmitting very little data.  Don't use a transceiver -
> just a transmitter.  Transmit about every 10-20 minutes, and during
> each transmission send the last 48 hours worth of data.  Send it twice
> with some data correction information, and you'll have a plenty
> reliable system.  This will also drastically lower the cost and power
> consumption of the device.  A pair of D cells could run it for a year
> depending on sensor consumption and time between level checks.
>
> 2. Yeah, you're going to have trouble sending any signal through
> concrete and snow.  Looks like there's rebar in the concrete too.  The
> best thing to do is overengineer it and try it out.  Keep in mind that
> lower frequencies penetrate better, so I'd look more in the 400mHz
> range and slower than up in the 900 or 2.4GHz range (ie, bluetooth,
> zigbee, and wifi will be poor).  You could go very low frequency if
> you enjoy designing radios.
>
> 3. Antenna design will be very important here.
>
> 4. For an interesting hack, use a pulley system with counterweights
> and floats, and attach it to a generator to power the system.  It only
> needs to operate if the water level is going up or down - otherwise
> it's the same.  The transmitter sends a pulse of a certain frequency
> going up, and a different frequency going down for each inch up or
> down.  A capacitor stores energy generated inbetween pulses for use
> during the pulse.  Given the huge power that can be generated from
> that much water moving up and down, this should provide plenty of
> energy, but it is very mechanical...
>
> 5. Rather than worrying about when the computer is on, build a
> receiver that attaches to the computer and has its own display that's
> always on.  That way he doesn't even need to power up the computer,
> and you can have an alarm.  Let this device do the logging, and keep
> the power and parts in the well cheap.
>
> 6. If the issue is drilling a hole in the concrete, you can put the
> receiver on the outside of the cap to maximize coupling, and then run
> cable to the house.  But at that point, is making a hole that big a
> deal?  Depends on on your county environmental health organization -
> could be that you'll have trouble if they ever inspect it (usually at
> sale or transfer).
>
> ...
>
> Well, I'd better stop there, or I'll start solving problems you don't have...
>
> -Adam
>
> On 10/9/07, Rolf <learr@rogers.com> wrote:
>   
>> Hi All.
>>     

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