I am building a little device for cloning plants. During the first week while the plants are rooting the humidity is held at 100%. Once the plants have rooted, they need to be 'hardened off' to ambient RH over the course of a couple days so that they aren't shocked by the dry air when they come out.
I plan on having a humidity sensor inside the cloner and a small computer-sized fan mounted on the outside that pulls air through the tub to reduce the humidity. The fan will be controlled by a smart switch.
How would I go about setting it up so that I could flip a switch in HA and then have it turn the fan on and off to maintain the RH at a set level that reduces over 48hours, ie starting at 100% and ending at 50% two days later? Just to make the math easier it could reduce by 1% every hour (-48% over 48 hours).
The idea is that when I first turn it on it holds the humidity at 99% for an hour, then the next hour it holds it at 98%, then an hour later 97%, etc. all the way down to 50% by the end of ~48hrs.
Hi, that fan you want to use is really for use with a computer?
If so, you cannot use a smart plug since those use different voltages compared to a computer fan.
Using a normal 110 / 220v fan could be easier since you can just hook that up to a smart plug.
All you have to do then is to measure the humidity and control the smartplug/fan so that the value is what you like it to be.
Hi, that fan you want to use is really for use with a computer?
If so, you cannot use a smart plug since those use different voltages compared to a computer fan.
The fan I'm using is made for cooling A/V cabinets so it's USB that plugs into a 110V wall wart, all good there!
All you have to do then is to measure the humidity and control the smartplug/fan so that the value is what you like it to be.
This is the bit I need help with, I do not know how to make a single toggle that will slowly step the humidity down over 48 hours.
Does the temperature matter or are you going to keep it constant? Are you going to have direct sunlight or grow lights?
The temperature is maintained by a seedling heat mat on a smart switch underneath the tub that uses the same temp / humidity sensor I plan on using to control the humidity. Thankfully the temp is static so that automation is pretty easy and already set up.
The light is a simple LED bulb on 24/7. Too much light causes plants to metabolize and eat themselves while they are cloning so low consistent levels of light are perfect.
Constant temp and light will make it much easier. A 5V fan can be controlled by an ESP32 with a 5V power supply. It can be turned on/off by a 5V relay or transistor/Mosfet. We don't know the size of your propagator so a single 5V fan may not be enough.
Automations can turn on/off the fan based on if it humidity goes below/above desired level. You would need to set that level based on an input number entity. That number can be decremented each hour by calling the service decrement.
Constant temp and light will make it much easier. A 5V fan can be controlled by an ESP32 with a 5V power supply. It can be turned on/off by a 5V relay or transistor/Mosfet.
The fan is 110V so no worries there, I'm just using a plain old smart switch for it.
Automations can turn on/off the fan based on if it humidity goes below/above desired level. You would need to set that level based on an input number entity. That number can be decremented each hour by calling the service decrement.
The thing I need help figuring out is how to script out an automation that will slowly lower the humidity setpoint 1% per hour over 48 hours. This decrement service possibly sounds like what I'm looking for but I don't know how to use it.
Have you considered just getting the chamber up to the desired humidity then turning the fan on and timing how long it takes to equilibrate to ambient? That should give you an gross estimate for total "fan-on" time needed. Combine that with Spiro's time pattern and counter, using the value of the input number to compare to the current humidity to see if the fan should run.
While you're at it, run a few tests with just small openings and no fan. Unless this is a large, tightly sealed enclosure, active ventilation may not be necessary at all. Through it might be useful to have the fan inside the container for circulation to combat the stack effect. How useful that would be is also going to be dictated by the size and shape of the container.
If you want to get fancy, there is a custom integration to create a PID Controller. The PID would work to maintain a steady humidity and your automation would just decrement the setpoint every hour.
The air will not stay inside a heated device with a fan mounted that allow air through even when it is not running.
Another issue is on the fan, which the s way too powerful.
A single 8cm fan is sometimes used for freezer in stores to freeze ice cream by the check out. That is how powerful they are.
The air will not stay inside a heated device with a fan mounted that allow air through even when it is not running.
Another issue is on the fan, which the s way too powerful.
A single 8cm fan is sometimes used for freezer in stores to freeze ice cream by the check out. That is how powerful they are.
I understand where you're coming from here but I've accounted for that. The intake side is 4x 3/4" holes in the tote and then the fan is mounted over the top of 2x 3/4" holes for exhaust. As you can imagine this makes the fan much less powerful. I keep the intake holes taped over for the 100% humidity portion of the cloning (first week), then un-tape when I'm ready for the fan-automated "hardening off" to start. The 2x 3/4" holes on the exhaust side do not need taped over as they do not drop the humidity appreciably on their own.
It's all set up and working and I can manually run the fan for 30-60 seconds to drop the humidity 1-2% and when the fan stops the humidity remains where it was until the plants transpiring causes it to rise again after an hour or so.
The humidity is caused by the moisture in the medium and the plants themselves transpiring. If I fill the tote with plants and close it the humidity will rapidly rise from ambient (~50%) to 100%.
