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Saturday, November 24, 2007
WxService Update Available
- WxService ow4j071124
- Added support for two more temperature sensors in the CSV history.
- Fixed a bug reading temperature on DS18B20 temperature sensors.
- WxMonitor ow4J071124
- Added support to display the additional columns for the CSV history.
If you update WxService, you will need to update all WxMonitor clients in order to display the wider CSV data.
(download the latest version)
Friday, November 23, 2007
Added WxService Tech Notes Page
I added a tech notes page for advanced users of the 1-Wire Weather Service for Java. I will periodically add new topics
as time permits.
WxService Update Available
- WxService ow4j071123
- Added support to automatically discover DS1920 or DS18S20, DS1822 and DS18B20 temperature sensors using family codes 0x10,
0x22, 0x28.
- Improved 1-Wire speed negotiation for better reliability.
Devices on the 1-Wire network sometimes get out of sync with the network speed. When a device stops responding, it needs
to re-negotiate the speed setting. This release adds that capability.
(download the latest version)
Tuesday, November 20, 2007
Dallas DS2438 Temperature / Humidity Sensor Bug
The DS2438 Smart Battery Monitor (A.K.A. Temperature / Humidity Sensor) has an analog to digital converter (ADC) with
two input channels, to read the power supply voltage (Vdd), and an external voltage source (Vad).
In the hygrometer application, a 1-Wire command tells the ADC to read the power supply voltage on the Vdd channel and
then the humidity sensor voltage on the Vad channel. Sporadically, the humidity module will suddenly report bizarre values,
sometimes far in excess of 100%, and then return to the actual value.
To diagnose the problem, I modified WxService to log the Vdd and Vad values, and I discovered that the channels were
sporadically getting swapped. In other words, when I ask for Vdd, I might get Vdd but sometimes Vad. When I ask for Vad, I
might get Vad but sometimes Vdd. This defect occurs with two different samples of DS2438. It is not my software, because the
same problem occurs using the 1-Wire viewer.
WxService can now filter out invalid reads due to swapped DS2438 channels, because the humidity sensor output on Vad
should always be less than Vdd by at least 0.5 volts (corresponding to roughly 100% humidity). If this is not the case, I
simply discard the reading and try again.
Sunday, November 18, 2007
My Rain Gauge Needs a New Battery
The other thing I noticed with all the restarts is that the rain gauge needs a new battery. Whenever the rain gauge loses
power, the DS2423 counters come up at random values, which makes the total accumulation following a restart anywhere from
0 to hundreds of inches of rain.
The battery is supposed to keep the rain gauge running and recording any rainfall even when the 1-Wire network is offline.
USB Adapter Locking Up
The Dallas USB adapter has been locking up since I bought the weather station, but it has been getting worse lately.
Especially whenever the wind gets above 20 MPH. That's pretty annoying, since the thing fails every time the weather gets
interesting.
I incorporated a watchdog timer that restarts the computer whenever no data is received for five minutes, but that should
be a last resort.
I finally got disgusted with the computer rebooting every five minutes, and ordered a powered serial adapter. Watch this
space for updates on how that works out for me.
Saturday, November 10, 2007
Humidity Sensor Flaking Out
My humidity sensor started reading erratically. I need to check my electronics box to see if I have another HIH-4000
or I'll have to order one and replace it.
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Welcome!
This site is dedicated to my interest in engineering. I use it as a place to just put stuff "out there" for anyone who
might be interested, as well as a job search tool. This page contains my engineering web log (to your left). Anything that
seems timeless enough, or too involved for a log entry may get it's own page as a full-blown article. And, of course, my resume
is here for anyone who might be considering hiring me to do something. Email me.
About Me
I have worked as a broadcast engineer, electronics designer (analog and digital) and software developer. I especially
enjoy audio engineering, although I've been writing software for the last several years, since that's where the opportunities
are in the Pacific Northwest (this is Microsoft country after all). I'm currently working as a Senior Staff Engineer -- Resume at another large independent software vendor in Washington State.
I majored in mathematics and physics in college. Other interests include music appreciation (baroque, classical and early
romantic, ragtime, and 60's and 70's rock & roll), high fidelity audio electronics, meteorology and of course, computing
hardware and software. I tend to think a lot like this guy.
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