Power from the shield
The shield makes no power of its own. Its 3V3 rows are the ESP32-S3's regulator output, its 5V row is USB power a diode down, and all thirty-six LEDs together take about ten milliamps of the 3.3 volt rail — a thin slice next to the chip's own radio.
Where the rows come from
The shield has no regulator, no battery connector and no power input. Every power row is one of the ESP32-S3's own pins, carried out to the edge:
- 3V3, twice at the top of the left edge. The output of the AMS1117 regulator on the ESP32-S3.
- 5V, once near the bottom of the left edge. The board's 5V pin: USB power after a Schottky diode, so about 4.6 V with a cable in.
- GND, once at the bottom of the left edge and three times on the right.
- RST, at the top of the left edge. Not power: connect it to ground for a moment and the board restarts.
Each of those is on both the male pin and the female socket, so there are two 3V3 pins, two 3V3 sockets and eight ground connections to choose from.
What the shield itself takes
The six inverter chips run from the 3V3 rail and take microamps while idle. The LEDs take the rest. Each LED sits in series with 5.1 kΩ across the 3.3 V rail, which comes to about a quarter of a milliamp once the LED's own voltage is taken off — about 10 mA with all thirty-six lit.
That is small next to what else is on the same rail. 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 to watch is the radio plus whatever you wire to a 3V3 row, and the LEDs are not a reason to worry about it.
Using the power rows
Small sensors, a display and a few modules: take 3.3 V and ground from the shield. That is what the rows are for.
Motors, relays, servos and long LED strips: give them their own supply and join its ground to one of the shield's GND rows. The regulator on the ESP32-S3 is small and linear, and it is also powering the chip that is running your sketch.
Something rated for 5 V: the 5V row, with a USB cable in. It is not regulated — it is whatever the USB port provides, less a diode.
When it does not work
That row 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 row only has voltage if you are feeding it yourself. Powering the board through a 3V3 row leaves 5V empty, because the regulator only passes current from 5 V down to 3.3 V, not 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 3V3 and GND close to the sensor, 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 you take from a 3V3 row warms it. Warm is normal. Too hot to touch means too much load, or a short between a 3V3 row and ground — unplug and check.
Fifteen contacts on a ribbon, and two numbers on the back to ignore.
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