Click Pichure to download schematic
1 - Housing - Your choice but because of
the envronment we recommend something waterproof.
A metal housing can double as a heat sink for the two SSRs - you
just mount the SSRs to the inside of the box.
one recommendation from www.digikey.com that is cast aluminum
and includes a mounting flange.
1 - MYPIN TA4-SSR PID Temperature
2 - 25A rated SSRs (Solid Sate Relays).
1 - K type thermocouple - use to measure temperature.
1 - Common wall outlet - but please read the
Outlet modification note below.
1 - Electric space heater -
available from Wal-Mart & other sources.
Note: This project was designed with an electric heater in mind. A
conventional thermostat will work better
gas heat used in larger greenhouses.
1 - Exhaust vent - can
be a re-purposed bathroom vent or a vent designed for your
1 - Heavy duty extension cord - rated for the current
that your space heater will draw.
The female end will be cut
off & the cord will be used to feed power to your controller
(at the most) - Wire for the internals of your project.
If your extension cord is long enough you can cut off about 3' off
the female end and use the wires for your internal wiring.
is managed by the controller's PID logic. We recommend that you
start with a temperature setting that's 10 - 15 degrees F above the
lowest temperature you want your greenhouse to reach over night & we
recommend that you monitor your temperature independent of this
controller until you are sure the heater you selected will maintain
your minimum desired temperature. Only then should you drop your
setting lower to conserve heat. We recommend that you run the PID in
auto-tune mode so that the controller auto-adapts to season changes.
The exhaust fan is managed by the AL1 setting with no PID action
- it's a simple on/off like a thermostat.
Sorry for not providing more specific
step-by-step instructions but how things go together depends a lot
on the housing you chose to build your project into. Later on we
will build one for ourselves and I'll include detailed instructions
on this page, but I can include a list of things to watch for.
1. Make sure that all internal wiring
between the incoming power cord and the power outlets is rated for
the current you will be drawing.
2. If you use a metal housing
make sure you run a ground wire from the housing to the green
(ground) wire coming from the extension cord.
KILLS!!! If you don't understand these instructions, or any part of
these instructions then call a qualified Electrician.
safety, always plug this controller into a GFCI protected outlet.
Outlet modification for this controller
Actual controller in operation
This is a video of the actual circuit in operation.
temperature is set to 50F and tha AL1 temperature is set to 80F to
demonstrate switching between heat and exhaust vent modes.
see the PID in action - the heater side switches more on on & less off
as the temperature gets closer to 50F.