Terrarium growing experiments - Page 13 - Orchid Board

Draikan · #**121** 04-07-2021, 07:45 PM

Hi fhopper!

Right now the system is a mix of MCU, outlet timers, and mistking timers. Eventually I will move all the control to the MCU, but I haven't had a chance to design and order an MCU breakout board with all the extra pump/fan/valve/sensor interfaces I want. I've been super focused on getting this first sensor version working great (the rest of the project is pretty worthless without a really great humidity sensor).

I am currently using the SHT35, but long term there is a chance I will switch to the HDC2022. The HDC2022 has similar moisture protection features and specifications, but it is much cheaper.

The heater is just an 0805 resistor right next to the humidity sensor. There is a relatively wide copper track between one of the resistor leads and the thermal pad under the SHT35 to help transfer the heat from the resistor to the humidity sensor. See the below image where the heater is circled in red, and the sensor is blue:

My tanks are pretty industrial looking, they aren't really display tanks. So I will be happy to just dangle the sensor in. If you put the sensor in a regular terrarium just make sure it has good airflow, it needs to get some circulation to measure accurately.

I will let you guys know when I get to something worthwhile for other people to test. I've shifted gears a bit on this project to consider possibly offering kits to other hobbyists. That adds some overhead to these first few versions but it should speed things up long term.

As an example, I need to test the waterproof coating I want to use to build larger volumes of sensors on this first batch, rather than just continuing to manually paint on nail polish. Unfortunately that stuff has a 12 week lead time, but I had to buy enough for A LOT of sensors so I should be good to go in the future.

fhopper · #**122** 04-08-2021, 01:37 PM

Thanks! Do you have a target MCU in mind for designing a breakout board for full automation and wifi?

Have you looked into a protective enclosure for the humidity sensor such as the one used by this dfrobot sensor assembly: SHT31 Weather-proof Temperature & Humidity Sensor - DFRobot ?

It looks like it may solve the issue of over/under exposure to the terrarium environment, assuming that the membrane allows enough airflow through and is water-resistant enough. I've been trying to find a cheap option to purchase the intake filter they use for their shield. It's quite similar to the reservoir filter from mistking but looks a bit shorter. Anyone know where to find something similar?

Draikan · #**123** 04-08-2021, 03:20 PM

I was originally using a SAMD51J19 based board from Adafruit, I think I link to it in earlier posts. It doesn't take much to read a couple sensors and control some valves. Most 32 bit Arduino based boards should be up to the job.

I have looked at the dfrobot sensor, and I built some similar enclosures earlier in the thread. I eventually gave up on them, because they do not solve the environmental exposure issues.

Mechanical protection only solves part of the issue. It will keep water and dust off the sensing element, but does nothing to control the humidity experienced by the sensor. You cannot leave the sensing element exposed to >80% humidity for more than a few hours without it absorbing moisture from the air and becoming inaccurate. The sensor does not have to get "wet" to become inaccurate, it just has to be in high humidity air. If you use a sensor with the PTFE membrane, you should have enough protection from dust/water/fingers/etc. to keep the sensing element from being damaged.

I experimented with mechanical protection and filters earlier in the thread. Eventually you will get water inside the housing, and the reduced airflow inside the housing combined with the water will cause the humidity inside the housing to be greater than the air you want to measure. I have had by far the most reliable results by coating the electronics for waterproofing, heating the sensor, and NOT using any kind of enclosure or air filter.

That said, I do eventually want to add a protective enclosure to my sensors, but it's purpose will be purely mechanical rather than for environmental protection. It would just be there to protect the thin sensing tips from bumping/dropping/etc. So the enclosure would be very open to airflow. I'd probably make the holes/slots just small enough to keep fingers and tiny critters out, but no smaller.

---------- Post added at 12:20 PM ---------- Previous post was at 11:05 AM ----------

I just noticed you were specifically asking about MCU+Wifi. I chose this board for my initial dev work for exactly that reason: Adafruit Metro M4 Express AirLift (WiFi) - Lite : ID 4000 : $34.95 : Adafruit Industries, Unique & fun DIY electronics and kits

fhopper · #**124** 04-08-2021, 06:13 PM

Gotcha, thanks for taking the time to reiterate some of the details from earlier in the thread. I look forward to seeing your continued progress. Keep the posts coming!

Draikan · #**125** 04-09-2021, 12:22 AM

I have been wanting to take better closeups of the flowers but didn't know how. My wife has a real camera and gave me some help tonight. I don't have too much in bloom at the moment, so we just did Stelis hirtzii and Pleurothallis eumecocaulon.

I never realized the P. eumecocaulon was transparent/silvery, I thought it was just white!

DirtyCoconuts · #**126** 04-09-2021, 09:00 AM

hey- slight derail, i have good vision and decent hand control but this is insanely small, it appears.

it is?

what tool do you use to see and do the soldering?

like the old school magnifier and alligator clips?

such GOOD work

the photos are nice too- try to hang a dark background - it helps for the macros to come out and for the camera to focus

Draikan · #**127** 04-09-2021, 12:29 PM

It is small, but it is mostly possible to do by hand. I'm decent with a soldering iron, but not as good as the technicians at work. I usually don't use a microscope, but they can be helpful for inspection. I do use the alligator clip helping hands, to hold everything still. And you need a decent soldering iron with a small chisel tip. A $10 radioshack iron is probably no good, but something temperature controlled for ~$50ish is probably fine, it doesn't need to be a professional grade tool.

The components in green are about 0.06" x 0.03", they are actually pretty easy to solder by hand with a little practice because there is just one solder joint on each end. The part marked with pink is a little more fiddly because the solder joints are so close together along the edges, sometimes you accidentally short them together, but it's possible even without magnification. The parts marked in red (the actual sensors) are harder because the solder connections are mostly underneath the part. I didn't wan't to solder the humidity sensor by hand, because there is actually a hidden pad under the component that would need hot air or an oven to solder well, and if I do a poor job (likely) it would probably damage the component and mess up the humidity accuracy. It would also be easy to accidentally overheat the part and melt the filter membrane.

So I did not solder these boards by hand, they were professionally assembled and reflowed. A solder paste is printed onto the copper pads of the circuit board, the components are placed into the pasted spots with a pick and place machine (like a cnc but instead of a cutting tip it has a tiny little vaccum tip to pick up and set down the parts), and then the whole thing is baked at a very carefully controlled temperature to melt all the solder joints at once.

I will try the background next time! We are also getting a small remote trigger for the camera so we don't shake it so much while taking the pictures.

DirtyCoconuts · #**128** 04-09-2021, 12:52 PM

hahaha- your humble normal is still amazing to me.

Iwatch "how its made" when i am bored at night and even watching computer driven machines make circuit boards is amazing...ill occasionally mutter "damn, that thing can solder/weld/bend!" and then be glad no one (awake) is in the room with me LOL

Draikan · #**129** 04-15-2021, 09:50 PM

We took a few more pictures tonight. Since the last two closeups I posted, we have added an extra light and a remote trigger. The trigger helps a lot to not shake the camera.

We are going to work on a better background before trying again. The plane of focus is very shallow for closeups like these, so I also need to find a way to get the whole flower in focus at once. You can see the tips of some of the petals get blurry.

Roberta · #**130** 04-15-2021, 10:36 PM

To have the entire flower in focus, I think that you're going to have to explore focus stacking. Software, plus a DSLR and some hardware to run the whole thing... it's a technique where multiple photographs with slightly different focal points are "stitched" together. Z-stacking is one option. You are up against the laws of optics... when very close, your depth of field will be small. With more light so that you can use a smaller aperture you can get a little more depth of field, but you're still pushing the limits of what is physically possible. So... yet another project??