AVR-Chat

On Friday 22 October 2004 06:51, Dingo wrote:
> If you only need to send data 400 feet you could look to 433MHz
> radio modules. (They are similar to Garage door remotes, but
> designed for serial data).
>
> I'm thinking a microcontroller at each end of the 400 feet. One to
> the device and the other into the serial or ethernet port.

Good idea. I've used (not built) a similar radio link for telemetry
from a solar car to a support vehicle. [The uC at both ends is an
AVR.] Initial experience was quite disappointing, with an effective
range of less than 30 metres.

> As for range on SAW wireless modules, some claim over a kilometre.
> To get this though would require a proper antenna I'd imagine. For
> 400 feet you could probably get away with just a nice small
> antenna. This really isn't my area though :)

With the solar car, we kept the original antenna (that was properly
tuned anyway) but increased the ground plane size from the original
sheet metal size of about 20 cm diameter, to one using two strips of
aluminium foil glued onto the exterior of the supporting fibreglass
panel; for an area of about a metre square. That was sufficient to
increase the reliable range to well over 50 metres which made the
experience rather more safe. At one time we were able to get
intermittent telemetry from over 100 metres; with the solar car
enclosed in a sheet-metal trailer!

A fixed installation shouldn't have too many ground-plane problems.

-- 
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