Differential Thermostat Kit
This low cost, high-quality, homemade 12 volt DC differential thermostat responds to the difference between solar collector temperature and heat storage temperature and regulates the on/off time of a 12 pump. It also displays the actual temperature inside the solar collector and inside the heat storage tank at any given time. The Digital Volt Meters are not a necessary part of differential thermostat regulation but they make a nice addition to the differential thermostat kit.
Without DVM meters this controller will still regulate the on and off time
of the pump, but if you're curious like me you'll probably want to know
how
hot your collectors are getting and you might also want to know how
much heat is being stored
inside the heat storage vault.
A permanent set of meters could be mounted as
illustrated above or one
meter could also be plugged into convenient test points to monitor
temperature
from time to time. The circuit to the right has three indicator
lamps that tell a story. The
green LED comes on when the pump is
activated. The top, red LED monitors collector
temperature and the
bottom, red LED monitors storage tank temperature. The temperature at
which these red indicator lamps come on may be set with the red
potentiometer (bottom right).
This additional circuitry is also unnecessary
as far as turning the pump on
and off. It's just nice to have visual indicators.
This brings us to a bare bones differential
controller that I've simplified as
much as possible without sacrificing durability and reliability.
This is a basic differential controller without all the frills. It has one black potentiometer that's used to adjust the on and off times of the pump. The terminal strip to the right is where all the external connections are made. I charge $100 for this controller assembled, but I sell kits for $29. Do you think you could assemble this differential controller from a kit?. I know you can. I'll even throw in a few extra components so you can build the controller with the indicator lamps. If you decide to build the one at the top of the page you'll need a to purchase a few DVM's. You'll also need a few temperature probes (not supplied with this kit). Solder not included.
So what do I get with the differential controller kit?
Thought you'd never ask!
To start with you'll get a partially stuffed bread board that looks like this.
The stuffed bread board ,mounted on plastic runners, is designed to get you off to a good start. It will contain an eight connector terminal strip, a 1K indicator pot, a 20K regulator pot, a quad op amp and a 12 volt, 10 amp DC relay. Installation of the other components as well as the wiring will be up to you. If you are not good with a soldering iron don't bother. I'll build it for you, but I do charge for that service.
I think I'll give it a try. What components will I get in addition to the bread board for $29.
a diode
AND a full set of
instructions for the electronic part of the project.
If you're a do-it-yourselfer I'm sure you can build and design a suitable frame
for the DVM's.
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