I am building an outdoor decorative holiday device, yeah, who isn't this time of year. Anyway, it requires a bit of amperage so I am using an open-frame A/C to 5vdc 10amp power supply and everything is wonderful on my bench. But I started thinking about it being outside, and if I should install a fan in my device to cool things down, and then I started thinking about moisture. Fog, rain, that sort of thing. The whole device is encased in a moderately large acrylic tube 2 inches in diameter. Should I seal it up to avoid moisture from shorting it out? Should I go ahead with a fan and hope the heat inside burns off any high-humidity issues?
The heart of the controller is an ESP-32 and a bunch of WS2812 LED's. 160 to be exact and although my math says max 9.6 amps at full all out LED's (3x60ma per led x 160), I do not expect my light show to max out more than 5 amps. I plan to install two temperature sensors... one inside and one outside in the next layer (inside a light fixture).
Am I over thinking this or what should I do to cool yet keep moisture out?
I would appreciate any advice I can get! And I certainly appreciate your time!
THANKS! - Hop
I'll suggest separating the power supply from the circuitry.
Put it in an aluminum box as heat sink and seal it in.
If the control circuitry builds any heat, do similar.
Big aluminum boxes are Great heat sinks. Depending on net heat it can be one box.
Venting, fans and openings in outdoor stuff is Real Trouble.
If you're north of the equator temps are already on your side.
I really like your approach to this. Unfortunately, the open-frame PSU barely fits into the acrylic tube I picked it for. And, I am not sure how I would sink it to an aluminum case considering the heat points of the switching PSU (yeah I do not fully understand the mechanics of a switching PSU) are all sinked individually on the board with their own heat sinks. I would have to heat pipe those smaller heat sinks to the enclosure, right?
I'll run tests on my bench and then put it out on the back patio to see how the ambient temperature affects the environment in the tube.
It's really something. You do not ever realize all that goes into a device's design including heat, etc. until you do it on your own.
Thanks for the reply!!
You can have a fan inside the Al box that flows over the heatsinks.
Get a $30 digital temp/humidity and put the sensor in the power box. Put the whole thing on the back porch && monitor it for a few days. If you want to get fancy, use temp/humidity sensors fro adafruit/sparkfun, an 8266, Arduino, and build yourself a sensor set for the interior of the box. Inside the house, use your other end of the 8266 to monitor and alert you if needed.
Post your project on instructables.com && send us the link! We want to see the video! (Can also send it to hackaday)
I've done holiday decorations for decades. Like CustomSarge said, if you're in the Northern Hemisphere temperature is unlikely to be a problem, particularly at night. Water, however, will be an issue. Seal the thing tight as a drum, or it will only be a matter of when, not if, water penetration, moist air and condensation corrodes and destroys the power supply. Been there done that. You can do some calculations for heat transfer (acrylic = 0.2W/meter/kelvin), but your idea of just testing it on the back porch is going to tell you more. In particular, you may find that the warmth the circuit generates is useful in preventing dew and condensation from forming on the outside of the tube. Those are the sort of real design challenges you don't find out about until you're "in the field" so to speak.
Thank you, everything replied here has been GREAT! You are right about testing. Without any data to see, I really have no idea until I put my prototype to the test. I am piggybacking a stm32f103c8t6 for peripherals and using a BME280 on the inside along with two or three DS18B20's on the PSU, the ESP32, and on the outside of the tube maybe. I have code I wrote for the ESP32 to serve websockets so my python script on my home headless debian linux server can log the data to a sqlite local folder database file. A few days through this while running the effects code will let me see more, and I should have done that before I posted. I was just thinking ahead and worried about bringing moist outside air into the thing to cool it. Again, if it was even needed.
I appreciate the big confirmation about outside moist air and my open-framed PSU. I promise to post more as this thing comes together mid-next week! :)
If you are concerned about "bringing moist outside air into the thing to cool it", what about to install an outside humidity sensor and bring outside air to cool the circuit only if the humidity is low?
Let me know if you'd be interested in writing a blog post about this project. If you are, I will update your account to give you access to the blogging interface. Thanks and good luck!