Power on the screw terminal base
The base makes no power of its own. The left block's 3V3 way is the ESP32-S3's regulator output, the right block's 5V way is USB power a diode down, and there is one of each. The radio is the load that moves, and a capacitor at the sensor is the cheap fix.
One of each
The base has no regulator, no battery connector and no power input. Every power way is one of the ESP32-S3's own pins carried out to a screw:
- 3V3 is the left block's top way. It is the output of the regulator on the ESP32-S3. The dev board has two 3V3 pins and the base ties both to this one way.
- 5V is the right block's top way. It is the dev board's 5V pin: USB power after a Schottky diode, so about 4.6 V with a cable in.
- GND is the second way of each block. All the grounds are one net.
- RST is not brought out.
3V3 is on the left only and 5V on the right only. A module on the right block that wants 3.3 V needs a wire across the board from the left block.
Where each one comes from
The 5V way is not regulated. It is whatever the USB port gives, less a diode, so it moves with the port and with the cable. Anything that wants a steady 5 V should have its own supply.
The 3V3 way is regulated, and the regulator is linear. It turns the difference between about 4.6 V in and 3.3 V out into heat, so every milliamp you take from the way warms it, and it is also the supply of the chip running your sketch.
The radio moves the load
The ESP32-S3's datasheet gives a peak of 340 mA while Wi-Fi transmits, in short bursts. A sensor on the 3V3 way sees the rail dip with each burst. A 100 µF capacitor across the sensor's supply pins, close to the sensor, supplies the burst locally. A USB port is meant to give 500 mA in total, so the budget is the chip plus whatever you wire to the way.
Motors, relays, servos and LED strips want their own supply. Join its ground to a GND way and nothing else.
What the base does not say
This page quotes no current rating for a terminal way or for the wire. The terminal is a JL102-35015G01; read its datasheet before pulling a heavy load through one screw. The limits that matter first are the regulator's, and they are much lower.
When it does not work
That way is the dev board'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 has voltage only if you feed it yourself. Powering the board through the 3V3 way leaves 5V empty, because the regulator only passes current down from 5 V 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 µF capacitor between the sensor's 3V3 and GND, turn 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 the 3V3 way warms it. Warm is normal. Too hot to touch means too much load, or a short between 3V3 and ground. Unplug and check.
An LED on GPIO 4 and a button on GPIO 5, wire by wire into the blocks.
A first build on the screw terminal base →Edit this page — content/books/esp32s3-base/screw-power.mdx
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