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[wxsig] X1W-2 Fan

John Bennett jabennett at insightbb.com
Tue Feb 13 00:42:29 UTC 2007


Understand that the boards were originally designed to support my WXN
server which doesn't run the fan unless the RH exceeds a specified
setpoint (default is 80% - can be altered in the wxnhostd.ini file).
Given Murphy's probabilities of blowing things up, I decided the best
place to put the PIO was on the inside board. It's easier to replace the
PIO there if it gets blown than if it's on the tower. Also, the T-238
does not support on/off control of the aspirator. The X1W-2 works in
both the T-238 and WXN enviroments. In the rev 2 version, the rain gauge
and EMP interface was duplicated on the -2 in hopes that it would be
incorporated into the T-238+ firmware (rain gauge does work - speaking
of the EMP interface). Will has expressed a desire to do so, but like
myself he is very busy. Hard to find time for much anything else except
eat, sleep and work it seems.

The idea of the aspirator is to improve the accuracy of the RH readings
at the high end to help prevent condensation from forming on the sensor.
If condensation forms, all bets are off for an accurate reading. The
idea was to turn off the aspirator when it was not needed to save the
fan bearings. Since I have started using them (several years now), not
one has failed except due to a direct lightning strike. Unfortunately I
have no frame of reference to using one that is on continuously since I
have never done this.

Accuracy at the high-end, incidentally, is a marked improvement with the
4000 series sensors over the earlier IC  Honeywell had out. Not one
failure to date, and seems to track very closely with NWS readings. The
older sensor used to saturate almost every night, regardless of
conditions. This is assuming the board has been properly sealed per my
suggestions in the manual.

If you are not running my server, you don't need the PIO switch. Just
hook up the power leads to 12V. If you use only the photo-cells to run
the aspirator, it would not run at night when it is needed the most
unless you have a fairly decent battery than can be charged - and then
you have more tower maintenance.

The -1 board has two such PIOs. Just because the are labeled 'Aspirator
Control' and 'Rain Gauge Heater Control' doesn't mean they have to be
used for that. If I ever get the time, I hope to do something in the way
of a remote I/O control board using these PIOs. They are inexpensive and
can be used for input as well as output. Ideal for simple on/off and
sensing applications. Lots of things you could do with them. But that's
another project.

Hope this helps you understand why the PIOs are there.


On Mon, 2007-02-12 at 08:28 -0800, Rasputin Novgorod wrote:
> The fan is installed in X1W-2 Humidty/Temperature Kit,
> but the strange thing to me is that the control for the fan 
> is located on the X1W-1 indoor barometer board, so you have
> to string more wires to connect them. 
> 1) I wondered about moving the fan controller to the fan
> baord, but then I suppose you have to string extra wires
> to provide power for the fan.
> 2) Instead, I was thinking of getting some photo-cells to
> power the fan. When the sun is shining and you need a fan,
> the fan would get power from the sun (photocells) and 
> start up.  I'm unsure how many cells I'd need, or about
> regulation. Any thoughts?
> Sincerely
> /b
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John Bennett
Evansville, IN
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