Frodo & PWMaster
Frodo Frodo
PWMaster PWMaster
Frodo Frodo
Hey, I heard you’re building a quiet fan array for a bookshelf—what kind of cooling curve are you targeting? I’ve been trying to keep my books at a nice temperature and could use some of your expertise.
PWMaster PWMaster
Yeah, the goal is a linear drop from 25°C at the top of the shelf to 22°C near the bottom, keeping the variance under 1.5°C across the stack. I’m using 12 V PWM fans set to 35 % duty, a 120 mm radiator for the heat sink, and a 0.1 µF ceramic at the fan supply for ripple suppression. That gives a 60 dB noise floor, so the only thing that’ll disturb you is a book falling off. What’s the layout you’re working with?
Frodo Frodo
Sounds like a tidy setup, but I’m a bit of a book‑worm, so I’ll just keep my shelf neat. If you can share a sketch of how you’re spacing the fans and the heat sink, I can see if the airflow will glide the temperature just right. I’ve got a couple of shelves stacked at about 30 cm apart, so let me know how you’re aligning the fans to keep the books cool without a thunderous hum.
PWMaster PWMaster
Sure thing. Picture a 120 mm fan mounted directly under each shelf, spaced 30 cm apart. The fan’s front air outlet faces the shelf surface, pulling the cooler air up from the bookshelf. Between the fan and the first shelf I keep a 0.5 mm spacer made from polycarbonate, just to prevent any back‑flow. The radiator sits beneath the fan array, attached to the same 12 V supply, and is a 200 mm by 80 mm copper plate with a 1 mm thermal pad on top. The fans run at 35 % PWM, which gives about 120 CFM per fan; that’s enough to push the stack’s heat out while staying below 60 dB. If you keep the shelves at 30 cm, the airflow will be steady enough that the temperature difference between the top and bottom shelves stays under 1.5 °C. That’s the layout in a nutshell.
Frodo Frodo
That sounds like a solid plan—nice that the fans stay quiet and the heat sink keeps the books cool. Just double‑check the spacer thickness; 0.5 mm should keep the air moving straight, but if the polycarbonate warps a bit, you might see a small gap. Also, keep an eye on the fan's lifespan; 35 % duty isn’t too harsh, but the copper plate will get warm over time. All in all, you’ll have a cool, steady shelf that won’t make any noise unless a book decides to fall. Good job on the design!
PWMaster PWMaster
Glad the numbers line up. I’ll run a quick thermal test with the 0.5 mm spacer in place to confirm no gaps, and log the fan’s temperature over a month. That should give us a solid data set for future tweaks. Thanks for the heads‑up.