Circuitrocks

May naayos akong customer issue last week, parang worth sharing kasi madalas mangyari ito.

Setup: regular ESP32 dev board, kabit sa laptop USB. Bare board, walang problema — boots, flashes, lahat OK. Pero ka-wire mo lang ng DHT22 (3.3V, GND, data line with 10k pull-up), boot loop agad. Sa serial monitor: Brownout detector was triggered.

Common reaction: blame the sensor, blame the board. Pero yung brownout detector is doing exactly what it should. The ESP32 wants a steady 3.3V rail, and a laptop USB port plus the onboard regulator can be borderline once may sumasagasa pa ng kuryente. Mas malala if cheap yung cable mo, or kung shared yung port with other USB devices.

Mga nakakatulong na fixes (in order of how often they solve it sa shop):

• Better USB cable. The cheapo "charging only" kind drops half a volt under load. Sayang lang yung debug time.
• Powered USB hub instead of plugging straight into the laptop.
• A 10–100µF electrolytic cap right across the sensor's 3.3V and GND. Smooths out yung dip pag may bigla yung sensor draw.
• External 5V into VIN, skip USB altogether.

Yung instinct na "siguro depekto yung board" — almost never. Power. Halos parati, power.

Pareho ba sa ESP8266? Iba kasi yung brownout behavior dun (mas marupok actually). Curious if naranasan din ng iba.

Confirming this from the shop side — about half ng "ESP32 not working" customers namin are brownout-from-USB issues. Yung other half are CH340 driver or counterfeit boards.

Trick na natutunan ko: probe yung 3.3V rail with an oscilloscope habang nag-bo-boot at nagco-connect sa WiFi yung board. Makikita mo yung sharp dip pag mag-fire ang WiFi radio — minsan 200mV+ down. Kahit hindi mag-trigger ng brownout reset on this run, that dip is your warning na soft yung supply for reliable operation.

External 5V supply or a beefier USB cable usually flattens it out. Solid yung cap suggestion sa original post — 100µF on 3.3V is a no-cost insurance.