Mini Green House
Green house is misleading, it's a seed starter pod for the basement. I have the light, I just need an insulated box.
Ok, so I did that and I don't like it. I want to do this with LEDs.
Build
- Get measurements 50"x18"x32"
- Layout design, get cut list
- Find spare timer
- Buy insulation
- Cut insulation
- Assemble
- Add blower
- Gather temp data
Heater Circuit
Only if necessary. Or if I really want to. But don't let it be an impediment to something good-enough
Use an RTC module and an Arduino. The RTC module will wake the Arduino every 10 minutes. If the temp is too low, it will turn on a small heater. It will also check the time and turn the light on or off as needed.
The heater can be pretty simple, just run a few volts through a power resistor and blow a small fan over it. At 5v and 0.75A I can use 8x 50 Ohm 1/2W in parallel That will handle 4 watts.
The light is a bit more of a challenge because I need a latching power relay. I also need a way to check the state of the light, not hard, but there's a few ways to do it. It might actually be easier to hook a servo up to a light switch.
Components
- Blower to circulate air
- Heater
- Light control
Build
- Start by just building the box - the light might be enough to keep the plants warm
- Add a fan - the air movement helps build stronger stems
- If the temperature is getting too low, add a circuit.
V2
- Power
- LEDS
- Fan
- Power resistor
- Power supply
- RTC
- Arduino
All electronics go inside the box. I don't need to worry too much about efficiency because heat is an issue.
Structure
Just foam insulation. I should probably cover the walls with aluminum foil to reflect the light.
LEDs
I can get an LED panel for about $25, but I'm not sure I trust those.
Plants have A and B chlorophyll see here
- A: 430nm and 662nm
- B: 453nm and 642
https://www2.mcdaniel.edu/Biology/botf99/photo/p3igments.html
So I want LEDs with peaks around those values. They should use about 50-80 watt/sqft
- 440nm blue led 1w : $4.00/50
- 660nm red 1w : $10/50
$14 for LEDs, not bad. And that 100w So about 14"x14"
The forward voltage is different, 3.2v for blue and 2.1v for red. But the current is the same 280-25mA.
Power
I'll clearly need 100W. 120w @$12, 240w@12v:$18, 2402@24v$12
I'll need a buck to drive the arduino.
Water
I'd like to setup a water reservoir that operates like a pet water bowl. Probably with something like a 2L as the tank. This not only makes sure that the plants have water, but it will also serve as a thermal reservoir.
Heat
I need a sensor, but I think I have some.
This depends on if the lights are on. If they are off, I should use more power and I may need it because the lights will generate a lot of heat. But if they are on, I need to limit the power.
I should also add an emergency cutoff - if the temperature gets too high, turn off the lights.
Interface
I'd like an LCD interface to display the data.