I would like to make a request to add three features to the FarmBot electronics box:
A weather & pest proof heat venting solution.
Thinking top & bottom louver style with fine mesh screen at top and bottom of sides (convection). Aluminum or plastic. Bonus would be to add a fan or two. Double bonus would be to have FB control the fan, say “On” if RazPi temp or outdoor temp exceeds x"
I found these:
(I am going to buy some of these and see if I can add them. I am thinking I will drill out a few holes, place and seal the vent, and figure out a way to block when the rains start. looks like I may need to replace or augment mesh right from the start - stock mesh looks big.)
Did you have a link to a specific document that you meant to link to?
There was no link in your post.
To answer your question, maybe one stepper driver in my early bring-up days, but not conclusive that it was due to heat.
I am, however, concerned with a) my current observations of the temps inside the box. During very mild days, the internal temp reached close to 130 or 140 F (55 to 60 C), and b) knowing heat is the enemy, I want to preemptively mitigate as much as possible. We can get up to 110 F (44-ish C) in the summer, and our FB is in full sun.
Reviving an old topic as my curiosity was piqued by some other discussions where I think thermal management would be important (see ramblings here)
I see two constraints that oppose or at least conflate each other:
Getting heat outside of the enclosure
Sealing the enclosure from the elements
A possible solution is to put a ‘double sided’ passive heat exchanger what has fins both on the inside and the outside of the enclosure. This allows the enclosure to stay (relatively) hermetically sealed and allows better heat transfer to the outside. I did a brief google search to find an example, but am falling short so far. Adding a circulating fan inside the enclosure could help with getting heat from the electronics’ heat sinks to the heat exchanger. You see this design pattern in telephone and cable communications equipment, as well as some power substations.
A more expensive idea (likely requiring a massive design change) would be to use a metal mounting system for the cards that touch the grounding pads to draw heat away from the boards. This metal mounting system would also connect directly to a heat exchanger with external heat sinks. This is a design pattern that exists in avionics units, but again, would likely be prohibitively expensive for Farmbot. I bring that solution up only to spark discussions.
For a different project from my day job I have some cooling experience. In a very cramped aluminum box I have an RK3399 with a bunch of components and a PoE+ power board. The environmental requirements for the project are pretty high so we were hoping to have it sealed aside from small gaps in the bearing surfaces. In the first design I had a thermoelectric cooler (TEC) sandwiched between the processor and the housing. It worked reasonably well for a month. After it failed, I opened the housing, and a stream of about 0.25 cups (60mL) of water poured out. There was that much condensate even through those tiny gaps. A couple of revisions later and the setup uses a 12V centrifugal fan with tiny ducts. The air intakes are twice the surface area of the fan’s intake and covered with fine stainless steel mesh. For the FB I would investigate copper mesh as it would be unappealing to many critters. Phone manufacturers also apply a hydrophobic coating (ala Scotch Guard) to one side of the mesh to keep the water out.
How well did this new design work after a month? Any condensate?
Also, how well does it perform during rain or high humidity? Would the hydrophobic coating would ‘clog’ during this period and reduce performance of the fans?
The latest revision has been working for months and performs well both for heat and high humidity and dust. Rain resistance is not a current design goal for that project. Also I have not tried coatings myself; I am simply aware of their use in cell phones. Cell phones are no forced air like we are referring to in the FB design. How about a small engine intake and just mesh on the exhaust: https://amazon.com/dp/B017DA4ZPU
I like the idea of the air filter on the intake!! Combined with some conformal coating (or similar like you mentioned for cell phones), this could be a relatively cheap and workable solution.
This spurred another thought: what if there was a metal tube that ran through the box, with a fan on the bottom to force air up, and a vented cap on the top. No air is entering the box. Inside the box, have a small fan to circulate air. In effect, the metal tube becomes the heat exchanger. The fan trades electrical and mechanical complexity for design complexity of a two sided heat exchanger. Obviously, that poor fan would have to be rated for the elements.
Bud Industries makes a variety HIGH QUALITY of weatherproof boxes in plastic and metals. They have air & moisture vents that you can attach a fan to. This may be a good way to go. You can attach a 60mm (P/N IPV-1115) or 80mm (P/N IPV-1116) fan to this, for example: