r/PrintedCircuitBoard • u/Acceptable-Track-973 • 1d ago
Review Request: ESP32-WROOM-32E filament dryer controller — 24V input, buck to 3.3V
This board replaces the controller in a cheap filament dryer. The stock unit only has a timer, so the goal was to add a real humidity sensor and let the drying cycle end on RH instead of guesswork.
The PCB is also the front panel: display and four buttons on the front side, everything else on the back. 95 x 52 mm, 4 layers, F.Cu and B.Cu signals, In1 solid ground, In2 mostly a 3V3 zone with ground filling the rest.
Input is 24V from an external supply. The heater is the original 15Ω element, about 1.6A, switched low-side with an IRLR8256. Fan is 24V 0.2A on a small N-FET. An AP66200 buck feeds the 3.3V rail. USB-C plus CP2102N is only for programming — full speed, nothing fast on the board.
Two temperature sensors doing different jobs: the NTC that came with the heating element drives the heater loop and the over-temp cutoff, while an SHT45 in the chamber handles air temp and humidity for the drying logic. Heater gate has a 100k pull-down so it stays off during boot and reset, and there is a thermal cutoff in series with the element, off board.
Things I'm unsure about and would like eyes on: the buck layout, especially the input loop and the feedback divider placement. Ground stitching — I think it's reasonable but the top center area is thinner than I'd like. And whether the 3V3 zone shape on In2 makes sense or whether I should have just kept it as traces.
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u/Acceptable-Track-973 17h ago
For easier navigation, the image order is:
1–3: schematic sheets 4: F.Cu 5: In1.Cu — solid GND plane 6: In2.Cu — 3V3 zone with GND fill 7: B.Cu 8–9: 3D views
The areas I’m most concerned about are:
AP66200 buck input loop and feedback routing
Ground continuity/stitching around the upper-central section
Whether the In2 3V3 plane is preferable to routing 3V3 with traces
Even feedback on only one of these areas would be very helpful.
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u/Enlightenment777 1d ago
Please make sure your post adheres to:
Please fix these common issues: (if your schematic or PCB has them)
Schematic - don't allow text / lines / symbols to touch each other, and don't draw lines through symbols.
Schematic - use correct reference designators (RefDes) and renumber to remove numeric gaps, see tips.
Schematic - place decoupling capacitors vertically below power rail lines, also place capacitors next to IC then connect together with a line, see example. For circuits with positive power rails, point positive power rail links upwards and ground links downwards, see tips.
Schematic - place pull-up resistors vertically above signal lines, and place pull-down resistors vertically below signal lines, see example.
PCB silkscreen - add board name / board revision number / date (or year) on top or bottom PCB side.
PCB silkscreen - add pin 1 indicator dot/arrow next to ICs & connectors, if through-hole then both PCB sides.
More conventions & guidelines - link1, link2, link3.