◗ PARTS LIST
Item
◗ C1, C2
◗ C3
◗ C4
◗ C5
Description
47 µF
0.1 µF
10 µF
330 µF
Source/Part No.
647-UVR1V470MDD
80-C315C104M5U
647-UVR1E100MDD
647-UVR1A331MED
◗ D1
◗ D2, D3
LED
1N4148
M859-LTL-4222N
512-1N4148
◗ J1
◗ J2
◗ J3
2.1 mm barrel
DB9-F, R/A
Pin socket
806-KLDX-0202-A
571-5747844-4
506-510-AG91D
◗ PB1
N.O. button
612-TL59F160Q
◗ Q1
◗ Q2
2N3906
2N3904
610-2N3906
610-2N3904
◗ R1 1K
◗ R2, Rf 10K
◗ R3-R6 4.7K
◗ R7-R14 100Ω
299-1K-RC
299-10K-RC
299-4.7K-RC
299-100-RC
◗ RES
50 MHz
Parallax; 250-05060
◗ TB1-TB5 Two-pos term
571-2828362
◗ U1
◗ U2
SX28AC/DP
ULN2803
Parallax; SX28AC/DP
595-ULN2803AN
◗ VR1
◗ X1-X9
LF50CP
Pin header
511-LF50CP
517-6111TG
All parts are from Mouser unless noted otherwise.
download file on the Nuts & Volts
website ( www.nutsvolts.com). It’s
very simple: Once a serial port has
been selected and opened, a timer is
started that sends the packet every 20
milliseconds. Sending it more
frequently makes no sense because
the servo framing timer is 20 milliseconds. It won’t hurt, of course, and you
can cause the control outputs to
change at the packet transmission rate
— so long as the transmission rate is
just over 11 byte periods long.
I think that 20 milliseconds is
probably a useful value for packet
transmission timing considering the
mechanical elements that are to be
controlled with the board (servos take
time to move). This will work with data
rates down to 9600 baud (which you
might want to use if the RS-232 cable
is long). Do keep in mind that the little
transistor level-shifter circuit is not true
RS-232; the TX level out is only 5V. If
you need a long transmission line, you
can replace these components with a
MAX232 or similar device. RA. 2 and
RA. 3 are available, so
they could be used
for hardware flow
control on a derivative
project, if required.
So, here’s an
opportunity to save an
old PC from the scrap
heap. It doesn’t take a
lot of resources to
send serial data, so
what I’m going to do is
reformat an old laptop
and devote it to
animatronics control
for Halloween and
Christmas. For me, the
next big question is the
PC development language; I tend to default
to VB because I have a
lot of practice with it,
but I would like to
work with others who
run different operating
systems (Mac, Linux,
etc.). So, I’m looking
for a cross-platform
development tool with
which I can develop
the same comfort as I
have with VB. Java seems to be the
leading contender, but if you have
another suggestion, I’m open to it.
Okay, that’s about it. Be sure to
study the full listing and don’t be
concerned if it doesn’t make sense
right away. When it does, a big smile
will cross your face and you’ll be off to
other things. Not too long ago, I helped
a customer in the Parallax SX forum to
mix VPs for “background” serial I/O
and Sony SIRCS decoding, and at the
moment I’m working on a serial-controlled lamp dimmer. Once you’re
used to mixing VPs, you’ll find that
you can control virtually anything —
virtually! Well, until next time, Happy
Stamping! NV
JON WILLIAMS
jwilliams@efx-tek.com
REPA
wSR
wwO ALL
.paUAX
rallR, I
ax.CNC
comE. S
www.sxlist.com
24
May 2007