Wine Cellar Controls: Simple analog control for Temperature and Humidity

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While not the most electronically-inclined individual, I am a computer
scientist--but have little grasp on the hardware (especially analog)
side of these things. I have the need to construct a control
mechanism for my wine cellar. Here are my specs:

1. I need two "threshold sensors," one for temperature (which will be
a thermostat) and one for humidity (is there such thing as a
"hygrostat"?). I only need them to act on two states: 'sufficient'
temp. and humidity, and 'insufficient.'

2. Coupled with these sensors will be a common space-heater and
humidifier. I need to know how I can create an intermediary"on/off"
switch to both of these 120V-A/C outlets. When the "insufficient"
state of either condition arises I want to complete a circuit that
will allow the heater/humidifier to run until the "sufficient" state
has been acheived and then terminate the circuit.

3. I need to know if this is even possible in the far less cost-
prohibitive analog realm. I could rig an overly-complicated DAQ-card
based and software-driven constant-polling set-up for #1), but still
would need help on the switching described in #2).


If anyone has an easy solution for me (and likes a good bottle of
wine, which I would be happy to offer as remittance) I would greatly
appreciative.

Thx all,

Luke

 

[JeffM]

I have the need to construct a control mechanism for my wine cellar.

The hubris of people on Usenet constanly amazes me
--people who think they have unique problems
which havn't been solved a billion times before
http://www.google.com/search?q=intitle:giyf+engine+-jargondb+-Mustang
and which don't have off-the-shelf solutions.
http://www.google.com/search?q=humidity-controller+OR+humidity-
controllers

 

[Homer J Simpson]

1. I need two "threshold sensors," one for temperature (which will be
a thermostat) and one for humidity (is there such thing as a
"hygrostat"?). I only need them to act on two states: 'sufficient'
temp. and humidity, and 'insufficient.'

Yes. Honeywell and other companies sell them. You should try Home Depot for
a start.

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[Fred Bartoli]

JeffM a écrit :

The hubris of people on Usenet constanly amazes me
--people who think they have unique problems
which havn't been solved a billion times before

He he, people which you are part of since there sure isn't a billion
people, err... family, equipped with a wine cellar, not even counting
their willingness to tightly control it

 

[John]

While not the most electronically-inclined individual, I am a computer
scientist--but have little grasp on the hardware (especially analog)
side of these things. I have the need to construct a control
mechanism for my wine cellar. Here are my specs:

1. I need two "threshold sensors," one for temperature (which will be
a thermostat) and one for humidity (is there such thing as a
"hygrostat"?). I only need them to act on two states: 'sufficient'
temp. and humidity, and 'insufficient.'

2. Coupled with these sensors will be a common space-heater and
humidifier. I need to know how I can create an intermediary"on/off"
switch to both of these 120V-A/C outlets. When the "insufficient"
state of either condition arises I want to complete a circuit that
will allow the heater/humidifier to run until the "sufficient" state
has been acheived and then terminate the circuit.

3. I need to know if this is even possible in the far less cost-
prohibitive analog realm. I could rig an overly-complicated DAQ-card
based and software-driven constant-polling set-up for #1), but still
would need help on the switching described in #2).


If anyone has an easy solution for me (and likes a good bottle of
wine, which I would be happy to offer as remittance) I would greatly
appreciative.

Thx all,

Luke

The simplest temperature control device would be a heater with a
thermostat - 1000 watt heaters are available for $20US (maybe half
that as they go on clearance - I just bought one at Lowe's for $10).

The next level of control is a line voltage thermostat which can
handle the power required by the heater (less than 10 amps for a 1000
watt heater). These are often over $100US new, but are usually
available on ebay for $25 - $50:
http://cgi.ebay.com/SIEMENS-Powers-...ryZ41988QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
You would need to mount the thermostat in a box with an adequate power
cord (rated the same as the space heater cord) and an outlet for
plugging in the heater.

Humidity controllers are not as readily available and most are
designed to interface to a low voltage control system of some type.
These need some eletrical/electronic interfacing to be able to control
apower to a humidifier. Ebay is also a good source for these ($25US
or less):
http://cgi.ebay.com/LIEBERT-SOLID-S...ryZ42911QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
http://cgi.ebay.com/Humidistat-made...ryZ71240QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://cgi.ebay.com/Honeywell-Wall-...3QQihZ017QQcategoryZ53301QQrdZ1QQcmdZViewItem

Digital temperature sensors are inexpensive (DS18B20 ~$5US), as are
low power microcontrollers (PICAXE 08M ~$4US). The code for a basic
temperature controller is available on the web for free:
http://www.picaxe.us/AV-fan.html (my site)
A solid state relay adequate to control a space heater is expensive
new but generally available in surplus for under $10US: (18A @ 240V)
http://www.mpja.com/productview.asp?product=16596+RL

A microcontroller could monitor both temperature and humidity and
control two solid state relays (heater, humidifier), plus provide a
status display - either simple on/off LED's or an LCD display the
shows current temperature & humidity plus on/off status of heater and
humidifier and out-of-range alarm capability (temp more than 5 degrees
from optimum, humidity more than 5 or 10% from optimum)..

Note that the microcontroller option allows mounting the temperature
and humidity sensors at their optimum locations in the area.

The choice is yours - Yugo, Ford, Lexus, Mercedes. It all depends on
where your needs and your budget meet ;-)

I can provide a plug-in solution of your choice in about 30 days
(longer if you want a finished wood case).

John

[picaxe] at [jecarter] dot [com]