F.Y.I.
The Radio part 's
available from * RFM * ( www.rfm.com )
now include the * TR 3001 * ,
which is a transciever
capable of 19.2 kbps using OOK modulation and up to 119 kbps
using ASK modulation
. The part cost $20 in low volume and $ 8 at 100,000 . It is just
now
rolling off the line and
samples are difficult to obtain. This model operates at 315 mhz.
and
they offer the same part in
other freq.'s ( 303 , 418 , 433 , 868 , 916 mhz.) .
The part has * Sleep * (150
uA ) and while operating , only consumes approx. 12 mA / Xmitting -
4 mA / Receiving.
Plus , in sleep , it can wake itself when a * Training -Preamble *
begins
to be received . . . .
.eliminating constant polling . Range is anywhere from over 300
feet
to less than 50 feet . . .
. depending on environment , output power ,etc .
They ( RFM ) have some good
* On-Line * designers guides under the * Applications Icon *,
and if you start now . . .
. . you may be able to determine how to setup your antenna by the
holidays : )
It's taking quite a while for me to narrow down a selection . . . . . . .
Regards . . . .
.
Steve Kelley
Protobyte Inc.
At 10:16 AM 9/26/99 -0700, you wrote:
>I'm
working a keyless entry system using the PIC16C84 and
would
>appreciate anyone's tips and or advice. I plan for the
system to run on
>a 4x3 keypad outside and it will unlock or lock the
door on a house when
>the proper code is
entered.
>Thanks.
>chris camerlin
>
Hi!
You may try
something like this:
use a 16F84 to read the keyboard, there are
applications on the AN, let me
see if I
can find one...(2 min wait
looking 4 it)...done, I couldn't find it, so:
A0
A1 A2 A3 <---outputs sequenced (see
below)
| | |
|
1----2----3----A-------B0 input
|
| | |
4----5----6----B-------B1
input <----typical keypad
|
| | |
7----8----9----C-------B2
input
| | |
|
*----0----#----D-------B3 input
you must add pulldown resistors
on all tree B inputs
the way of use it is sequencing (high) the
inputs A1..A3 (only 1 on at once) and
reading the outputs, if (for
example) B1 is high when A2 is selected, then the
digit 6 was
pressed.
Now the easiest way to send it to the central is IMHO using
RS232, because only
3 wires are necesary (Power, ground and data out),
and you also can doit
wireless,
it is more complex and a little more
expensive but no wiring needed to the
central.
some time ago I did
something like that with RFM modules (encapsulated
transmitters
that
works at 400 mhz with ON/OFF modulation at 1200 baud (RX1000/TX1000
model))
each key pressed can be transmitted via RS232 to the central,
for extra
security you
can isolate Rs232 with optocoupler and power
the keypad with a different
power supply,
so if some kind of short or
destruction ocurrs on the pad, it will not
affect the
normal operation
of the central.
I have some PDF's of RFM modules and some simple
Rs232 routines (without
using prescaler), If you need it, let me
know.
did you have the mechanical part solved?.
I hope it will
helpful.
Leandro J. Laporta (LU2AOQ)
mail:
lu2aoq@yahoo.com
wrk:
Arg. Assoc. for Space Technology.
ham: TCP/IP high speed
group HSG