Week 25: 2/6/2023 - 2/13/2023

Ian's primary objective for this week was to finish the control box build. All connections to the MCU were made in the previous week, so this week the connections to the terminal blocks had to be soldered. Ian started by soldering the connections from the transistor array to the fan terminal blocks.

The image below shows the fan terminal blocks from the MCU perspective. Wire color coding was done in rainbow order, such that yellow corresponds to transistor 0, green to transistor 1, and so on.

From the fan terminal block perspective.

Next, the power connections from the buck/boost converter were soldered to the transistor array rails.

Next, connections from the MCU board to the sensor terminal blocks were made. The sensor wires were color coded to the chart below, where K stands for Kathode and A for Anode.

The wiring to the terminal blocks is shown below. The green wire coming from the PCF8575 board goes to the green indicator LED anode.

With all connections made to the terminal blocks, the next step was to create wiring harnesses to run the cables from the terminal blocks to the windows. Ian started with the sensor terminal blocks.

Next, the wiring for the fan terminal blocks was completed.

Finally, the IP65 connectors were soldered to the freshly created wiring harnesses. These allow the control box to be easily disconnected from the fans. With this, the control box build was complete.

As shown in the group report for this week, some testing was completed on the weekend following build completion. The group report also details that the Raspberry Pi Pico was cooked in testing the battery monitor circuit. Once the group received the new Pico, Ian connected it to his computer and made sure that it operated properly. He also configured it to operate on CircuitPython. Next, Ian desoldered the old Pico and removed it from the PCB. This process was made remarkably painless by the Weller solder sucker at Valencia College. Finally, Ian installed the new Pico and soldered all the connections. The image below shows the new Pico.

While Daniel was finishing up the connections for the cables between the control box and fans, Ian retested the sensors with the new Pico, starting with the temperature sensors. He used a digital clock thermometer in the room for comparison. The results from the sample below indicate that the sensors ran anywhere from 0.3 °C to 2.3 °C hotter than the control thermometer. This may have been due to the positioning of the sensors in the room, and further testing over an extended period would be useful to calibrate them to an average.

Next, Ian set about testing the IR proximity sensors. A couple of the wires snapped off from their solder joints, so Ian fixed that first. Next, he ran the IR sensor test program. Interestingly, the proximity levels were an order of magnitude larger than the day before and also behaved inversely. In the previous test, the proximity levels decreased as objects approached the sensors. In this test, the proximity increased as objects approached the sensors. Regardless, the behavior of the sensors is still desirable, and a quick adjustment to the threshold fixed the program operation. Ian set the threshold to 48000. In the images below, the green LED is on when no object is present. When an object gets close enough to the sensor, the proximity level rises above 48000, and the program turns off the LED.

The battery monitor circuit will be retested in the coming week. Testing the sensors made clear that it may have been more efficient to wire all the sensor terminal blocks to the MCU first and test them before wiring the transistor array. The bulkiness of the transistor array made troubleshooting the sensors a bit more challenging.