From: Mark Fergerson
Organization: @Home Network Member
X-Mailer: Mozilla 4.61 [en]C-AtHome0407 (Win98; U)
Subject: Re: wanted: telemmetry micro transmitter schematics needed
Date: Wed, 30 Oct 2002 18:21:21 GMT
NNTP-Posting-Date: Wed, 30 Oct 2002 13:21:21 EST
"Pablo Rodríguez Barreiro" wrote:
> Hello, i've to develop a project related to biology, and i need to find some
> info about schematics of micro radio transmitters (216Mhz).
> I know they are implemented with quartz crystal and discrete elements, cause
> they are only about 1,5 cm long and they've very specific application.
> And also are very light.
> The system works with button batteries (2x1,5 volts).
Long ago, I read an article in (I
think) the late, lamented
Radio-Electronics about building a
swallowable thermometer built around a
very simple, low power one-transistor LC
oscillator. There was a calibratable
temperature-sensitive capacitor in the
tank circuit that determined the
frequency. It used two mercury button
cells, and was encapsulated in epoxy
with the cap not-quite exposed (battery
life wasn't an issue because the device
didn't stay in the digestive tract long
enough for them to die). The data was
recovered with a simple whip or coil
antenna attached to a chart recorder.
It was mentioned that other sensors
could be implemented frinst using
exposed electrodes to monitor pH changes
and like that, but no details were
given. Today you could probably build a
sound sensor using a tiny piezo speaker
(not available back then) as a
Sorry I can't remember exactly what
year, much less issue. But remember this
was before surface mount transistors,
much less s.m. IC's. I'm sure much more
could be done with today's parts.
A quick Google using the search term
'miniaturized +biotelemetry' turned up
many pages of stuff that you might find
Mark L. Fergerson