I've finished a relatively simple project to control some large 12V linear actuators using an Uno and 12V relays. 12VDC, 10A is fed from a standard power supply through the relays which are controlled by the uno board. This will run continuously outside for 12-18 hours and I have some concerns with heat. There is a chance of rain, so I've modified a plastic ammo box to hold the power supply, the uno and the relays.
I followed this project to connect everything:
The only difference is I programmed the relays to switch after a given amount of time rather than using push buttons.
Do I need to be concerned with overheating these little components? The motor on the actuator gets warm after 10 minutes or so, but I don't know if the Uno, relays, or power supply will generate too much heat and stop working. Does anyone have better ideas to waterproof and ventilate these components?
but I don't know if the Uno, relays, or power supply will generate too much heat and stop working.
If everything is wired correctly the Arduino just sends a low-current "signal" to the relay driver so you're not stressing the Arduino at all. Generally relays can be left-on continuously with no problems, but with linear actuators the relays can't be on more than half of the time. I can't tell you anything else about your other components.
It's generally a good idea to "derate" components. If you need 10 Amps, use a 12 or 15-amp power supply, and if the actuators are lifting 10 lbs, get actuators rated for 15 or 20 lbs, etc.
Does anyone have better ideas to waterproof and ventilate these components?
That's a difficult question. If you seal it in a box, you'll trap-in the existing humidity. Humidity alone isn't a problem, but when it gets cold the humidity will condense (turn to liquid). If there's enough heat generated continuously internally that shouldn't be problem. And, most outdoor electronics seems to be sealed inside a waterproof box.
Sometimes conformal coating can be used to seal/encapsulate a circuit board but it makes it unserviceable and you can't coat the connectors.
You might try sticking it in your freezer before sealing it up (there is no humidity below freezing) and/or you can get a desiccant and seal it inside.