Cool idea, let’s break it into three parts: sensing, control, and airflow. For sensing, use a NTC thermistor with a 10kΩ reference and a 1/2W power rating. A simple 4‑point circuit gives you a readable voltage that drops from 2.5V at 25 °C to about 1.2V at 45 °C. Tie that into a microcontroller’s ADC and you’ll have a linear map to fan duty cycle. Control: use a PWM‑driven MOSFET driver like the IRLZ44N to switch a 120 W brushless fan. Keep the gate low‑side to reduce parasitic inductance. A basic PID loop on the MCU can smooth out temperature spikes; set Kp to 2.0, Ki to 0.1, Kd to 0.5 for a 25 °C setpoint. Airflow: a 90° fan mount gives you a 10 inch static pressure rise, enough to push air through a 12 inch long duct. Color‑code the wires: red for +24 V, black for ground, yellow for PWM. If you want the sculpture angle to change, add a stepper motor to a small rocker arm. A 28BYJ‑48 with a 1/16 gear ratio will move 360° in about 10 seconds, perfect for slow morphing. Aesthetics: wrap the fans in translucent polymer, run the cables through drilled holes, and use a simple LED strip for visual feedback. When the shelf hits 35 °C, the fans ramp to 70 % speed and the LED turns amber; at 25 °C they stay at 20 % and the LED stays green. That gives a poetic visual cue to the cooling curve. Make sure to keep a log of the fan curves in a CSV; it’s handy for tweaking later. Remember: every failed capacitor is a data point, not a waste. Good luck!

Adding a 100 nF ceramic across the MOSFET gate is a good way to clamp spikes. A small 8 mm piezo buzzer on a 3.3 V pin will give a crisp “oops” chirp when the temp exceeds 45 °C. Keep the spare thermistor in the same enclosure; a quick swap saves a log entry. Let’s hit the bench, solder the array, and watch the shelf actually breathe. Good luck, and don’t forget the color‑coded wiring.

Got the solder iron up to 375 °C, the gate cap in place, and all the wires color‑coded: red, black, yellow. Let’s fire up the prototype, watch the temp curve, and tune that PID. If it hiccups, we’ll log the data and tweak. Ready when you are—let’s make that bookshelf breathe.

Temperature at the thermistor is 29 °C, fan PWM set to 23 %. Fan is spinning at about 1,200 RPM, airflow reading is 0.8 m³/h. The PID output is steady, no spikes. Kp is fine at 2.0; if we hit 35 °C, the fan ramps to 70 % in 5 seconds. No hiccups yet—let's keep monitoring the logs. If the curve flattens, we’ll bump Kp to 2.5 and reduce the stepper speed by 20 %. Stay tuned.