Sunday, March 12, 2023

Battery Box Cooling Project

Friday - Most of today was spent messing around with the D1mini microprocessor. I think I've run into some CPU limitations. If I added one of the small OLED displays, it wouldn't reliably connect to WiFi. If I set the PWM frequency, which controls the fan speed, too high, WiFi would disconnect and reconnect and the temperature wouldn't reliably feed to the HomeAssistant server. So, it is back to "simple mode" and I'm just measuring the temperature every 15 seconds and recalculating the fan speed (as a percentage) based on my hard set lower and upper temperatures and the minimum fan speed. For testing, I used 20% as a minimum, 25°C as the lower temperature, and 37°F as the upper temperature. The fan speed is linear over that range from 20% to 100%. If the temperature is below the minimum, a relay cuts power to the fan as even with PWM at 0, the fan would still be turning.

I did this on a project board and now will be moving the project onto a breadboard which will fit in the small weatherproof boxes I've been using for these microprocessors. All of these components are incredibly cheap and I still have a small bin of these bits and pieces from other projects.

One of the differences between the D1mini and the other 8266 microprocessors is that everything is 3.3V instead of 5V. So I’m using a bi-directional logic level converter between the microprocessor I/O ports and the other components. Very inexpensive component and it seems to work. I’m not running the PWM signal through it to the fan just the temperature sensor and relay board.

At 4 on Fridays is the park-sponsored happy hour with complimentary drinks (free beer, wine, soda) and live music. It’s too loud to carry on a conversation but it’s nice. This is the group that we’ve gotten to know during our time here. Last fall, most of them were across the street. 

Saturday - A morning test session on a cool morning. Its only 64°F mid-morning. Waiting for a test session to start up. The high is forecast to be in the mid-70s (°F) which is ideal.

Maybe I'll work on the circuit board out here under the awning this afternoon. I tend to have a lot of stuff out on the table when I work on one of these projects. I need to get it wired up before I forget how I made the circuit. I guess I could always make a schematic...

 - Another beautiful day here in Tucson. In the middle of the afternoon, it was a very pleasant 76°F with high clouds. Nice enough to make a mess outside instead of the dining table. I accidentally shorted out the buck converter which put 12V on the 5V buss. So I had to replace the temperature sensor and the microprocessor. Fortunately, I have spares…

It’s time to try and fit this into a weather-proof box and see if it’ll still connect to WiFi. 

After a dip in the hot tub, we sat by one of the fire pits around the pool. I keep forgetting to check them out during the day to find the valve and igniter. They are pretty nice. 

BTW, WiFi connectivity is pretty sporadic from the Faraday cage of a battery compartment. 

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