I built a serial port temp. sensor years ago based on this fella's
And just bought kit 145 from carl's electronics:
The unit uses DS1820 temp sensors and connects to the pc serial port.
There is a fifty foot run from the computer to the sensor.
My better half made me quit using it because of AM radio interference.
There is a constant beep beep beep.
I'm once again in need of 24 X 7 temp. logging. Is there an easy way
to salvage this unit? Or am I better off to just start over with some
sort of analog unit?
Start with the basics. Is the cable shielded with the shields
terminated? You should be running shielded twisted pair, and the cable
signal lines should be terminated at both ends. Are the circuit boards
in a grounded metal enclosure? If the system is shielded, the next step
will be to wrap a few turns of the cables around a ferrite attenuator
core, as Jim suggests. If it were in my heart and lung machine I would
add .1uF monolythic ceramic capacitors to the output of the DTS line at
the computer and the input of the voltage regulator on the board.
Separation of the data cable and the AM antenna will help. Running the
cable close to the ground or in metallic conduit will help. An external
AM antenna for the radio (away from the data line) will help.
You didnt say if it worked....assume it did....
Short of a lot of stuffing around, the clamp on ferrite interference
cores are worth a try - then try
if the cables you have run have spare conductors, ground them all at
each end. Maybe double up on the power one on pin 8 - the thing gets
its power from the receiving computer, could be a bit iffy what with
voltage drop on your feed cable...
Oh, and BTW Karl - you are aware you are committing a Federal Offense
by running an unlicensed radio transmitter causing interference to
your wifes radio. Possibly a lot of other radios as well.. Tsk
Buy her a bloody FM radio! Better yet, a sat radio, with none of the
farkin' commercials playing all the time.
Threee days before Tucson, Howard Dean explained that the
tea party movement is "the last gasp of the generation that
has trouble with diversity." Rising to the challenge of
lowering his reputation and the tone of public discourse,
Dean smeared tea partiers as racists: They oppose Obama's
agenda, Obama is African-American, ergo...
Let us hope that Dean is the last gasp of the generation
of liberals whose default position in any argument is to
indict opponents as racists. This McCarthyism of the left
-- devoid of intellectual content, unsupported by data --
is a mental tic, not an idea but a tactic for avoiding
engagement with ideas. It expresses limitless contempt for
the American people, who have reciprocated by reducing
liberalism to its current characteristics of electoral
weakness and bad sociology. --George Will 14 JAN 2011
Article titled "Tragedies often spark plenty of analysis"
Professor Will appears to have jumped the gun. Here's the latest example:
" [R]espondents were asked whether they agreed with various
characterizations of different racial groups. Only 35 percent of those who
strongly approve of the tea party agreed that blacks are hardworking,
compared with 55 percent of those who strongly disapprove of the tea party.
On whether blacks were intelligent, 45 percent of the tea-party supporters
agreed, compared with 59 percent of the tea-party opponents. And on the
issue of whether blacks were trustworthy, 41 percent of the tea-party
supporters agreed, compared with 57 percent of the tea-party opponents.
"The survey, which included about 1,000 respondents in six battleground
states (like Michigan and Nevada) and California, found similar margins on
questions regarding Latinos."
George tends to fall in love with his own rhetorical skills and to go off
half-cocked when he thinks he has a great insight. His "insight" this time
appears to be that the Tea Party is the second coming of his beloved Burkean
conservatives, with a strong libertarian bent. The evidence is that not
everyone in the Tea Party is a racist, but that racists seem to gravitate
toward the Tea Party -- something like Muslims and terrorists.
20 mA current loop, with shielded twisted pair. Maybe RS-485 for that
distance, although I've run cat5 LAN cable 100 feet before.
The secret to minimizing interference to the radio is twisted pair
and shielding. I recommend you get enough conductors so that you can
also use DTR/DSR and RTS/CTS, if only for the sake of completeness.
And again, use twisted pairs and shield the cable. Ground the shield
ONLY at the host end, so that you don't get a mongo ground loop.
I've been running a 1 wire system using DS18S20s driven by a DS9097U
for over three years and haven't had any AM radio interference. I am
a AM radio listener with about six radios that are spread around the house.
I have two bedside radios I use at night for weak signals, so if I had
I would have tracked it down in short order.
I have 13 freezers that I monitor on a real time basis, although the
program I use
will save and graph data.
You might look up the DS9097U as a driver unit. But I think now they have
USB connections so the numbers may change.
The program I use is Lampomitari, it does exactly what I wanted but
the best or easiest program to use.
I'll check in when I have more time to see if I can get you more info.
The only American citizens who are not "natural born" are those who
immigrated (legally) and then did the whole citizenship thing. Being
born in another country is still "natural born" if one or both of your
parents are American citizens. The "birthers" whining about this are
simply morons, whether they are racist or not.
I still do not support Obummer, and I am certainly no racist. Though as
a centrist I do agree with his positions on some issues, I disagree with
his positions on enough issues to not be able to support him.
It would be interesting if the same questions were asked about white
folks. It could be that members of the Tea Party have a lower opinion
about everyone. In fact I would expect members of a group that thinks
the government is not hard working, trustworthy, or intelligent, would
also think everyone is the same way.
Fortunately, the serial port has slew-rate limited signals and shouldn't be
an issue. The DS1820 (new ones are DS18S20) one-wire interface,
though, isn't so limited. If you use twisted pair wiring, and maybe a few
ferrite beads or 'clamp filter' units, it'll get better. To avoid ground
loops, ensure none of the distant end (sensor) wires touch any nearby