Power on the pluggable terminal base
The base makes no power of its own. Its 3V3 ways are the ESP32-S3's regulator output, its 5V way is USB a diode down, and the terminals' 8 A rating is the terminal's, not the supply's: what the ways can give is what the ESP32-S3's pins can.
Which ways carry what
Each edge has a 4-way power block above its signal block:
- Left: 3V3, 3V3, GND, GND.
- Right: 5V, 3V3, GND, GND.
Every one is a pin of the ESP32-S3 carried out to a terminal. There is no regulator, no battery connector and no power input on the base. All four GND ways are one net with the ground sockets, so any of them will do. The 3V3 ways are the output of the AMS1117 regulator on the ESP32-S3. The 5V way is the board's 5V pin.
Where the volts come from
With a USB cable in, the 5V pin is USB power after a Schottky diode, about 4.6 V. With no cable it is empty unless you feed it, and feeding it with 5 V runs the board through its own regulator. The diode points from the USB sockets to the pin, so it also keeps your 5 V supply from pushing into the USB port. The higher of the two sets the rail, so feed it with the cable out.
The 3V3 ways are outputs. Take a sensor's supply from them. Do not feed 3.3 V into one with a cable plugged in: two supplies would be driving the same rail.
What the ways can give
The terminals are a Kangnex WJ250B-3.5, and a parts distributor lists 8 A a way. That is the terminal's rating, not the base's. What a way supplies is what is behind it:
- The 3V3 rail is one small linear regulator, which is also powering the chip running your sketch.
- The ESP32-S3's datasheet gives a peak of 340 mA while Wi-Fi transmits.
- A computer's USB port is meant to supply 500 mA in total.
So the budget is the radio plus whatever you wire to a 3V3 way. Small sensors, a display and a few modules fit. Motors, relays, servos and LED strips want their own supply: join its ground to a GND way and leave its power off the 3V3 ways.
The burst
A Wi-Fi transmit is a spike of a few hundred milliamps for a few milliseconds. The rail sags for that long, and a sensor on the same way can see the sag as a reset or a bad reading. A 100 uF capacitor across the sensor's supply, as close to the sensor as you can get it, holds the rail up through the burst. It is the first thing to try when a board only misbehaves once Wi-Fi is on.
When it does not work
That way is the ESP32-S3's 5V pin, which sits behind a Schottky diode from the USB sockets. The diode costs three or four tenths of a volt. Nothing is wrong, and anything rated for 5 V runs from it.
With no USB cable in, the 5V way only has voltage if you feed it. Powering through a 3V3 way leaves the 5V way empty, because the regulator only passes current from 5 V down to 3.3 V, never back up.
The radio draws a burst of a few hundred milliamps as it transmits, and a load on the same rail makes the dip deeper. Add a 100 uF capacitor between a 3V3 way and a GND way close to the sensor, turn the transmit power down, or give the load its own supply.
A linear regulator turns the difference between its input and 3.3 V into heat, so every milliamp taken from a 3V3 way warms it. Warm is normal. Too hot to touch means too much load, or a short between a 3V3 way and ground: unplug and check, then check the board is the right way round.
An LED and a button, wire by wire, into the push-in ways.
A first build on the pluggable terminal base →Edit this page — content/books/esp32s3-base/pluggable-power.mdx
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