Order Tray | Contact Us | Home | SIG Lists

[wxsig] Wind Speed Spike

Will Beals will at beals5.com
Sun Jul 9 14:06:41 UTC 2006


To your second question:

I have three pins on the 1-wire bus in order to provide sufficient drive
strength for the "active high" state needed for some 1-wire sensors like the
DS18S20 temperature sensor.  The active high state is defined to allow some
sensors that temporarily need more than the paracitic power provided by the
pull-up resistor in order perform some function.  The suggested circuit for
this active high state is a FET driven by a control line.  I "cheated" (I
call it optimized) by just ganging three IO pins together to supply the
needed current rather than have the external FET.

That is a long winded way of saying (unfortunately) that you can't separate
the lines.  I need all three tied together to drive high  to supply the
current needed for the temperature sensor.  For regular communications only
drive low on PortB bit 0 only and sense on Port B bit 0 only.  


-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
Behalf Of Ken Brown
Sent: Saturday, July 08, 2006 5:51 PM
To: wxsig at lists.tapr.org
Subject: [wxsig] Wind Speed Spike


Several times in the last couple of weeks I have had a wind speed spike of
199g099.  This is since the nearby lightning event that caused several
other, seemingly resettable problems in the weather station and other
equipment.  That was also when the MAX232 chip failed and the barometer
became erratic.  The barometer is now plugged into a test T238 that has no
outside sensors and seems to be fine.  The status messages for a couple of
hours before, the affected line and several after are included below.  The
wind sensor is an original Dallas Semi although purchased from AAG.

normal data at 1404z 01080B350D55FED1
normal data at 1504z 01080B350D0CFEBF
(line wrap) P000r000h61e1w 03AC1DFFFF53E23A normal data at 1604z
01080C350D16FCC0 normal data at 1704z 01080D350D19FDC2

I had a similar problem a year or more ago and I changed the T238, wind
sensor, and wiring.  I don't know what may have cleared it at that time.

On another subject, I notice on the schematic that you use three pins on the
CPU to generate the one wire bus.  I assume this is to improve fan-out.  Are
all three pins the same or do you transmit on two and receive on one?  I ask
because I thought I might try to separate the one wire lines going to my
wind, temp/rh/rain, and barometer, by separating the transmit and receive
lines into some external devices to create three one wire bus lines.

Ken Brown

wxsig mailing list
wxsig at lists.tapr.org

More information about the wxsig mailing list