dfrobot Gravity: Analog EMG Sensor by OYMotion

AI context

Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.

PART: DFRobot Gravity: Analog EMG Sensor, SKU SEN0240, made with OYMotion. Two boards in the box: a 22 x 35 mm signal-conditioner board and a 22 x 35 mm dry-electrode plate, joined by a 50 cm PJ-342 lead. The vendor names no silicon part number on the product page or the wiki, so there is no part and no data sheet.
ADDRESSES: none. The output is one analogue voltage, so buses and addresses are both empty and there is nothing to scan.
PINOUT: DFRobot's own pinout table numbers four rows and those numbers are kept: 1 = A, analogue signal output 0 to 3.0 V; 2 = +, power supply anode 3.3 to 5.5 V; 3 = -, power supply cathode 0 V; 4 = PJ-342, the electrode probe jack, which is a connector row in the same table rather than a wire pad on the 3-pin cable. The board-side connector is a PH2.0-3P.
SUPPLY: 3.3 V to 5.5 V on pad 2. The wiki also lists an operating voltage of 3.0 V, which is the conditioner's own internal rail, not a second input range.
OUTPUT: 0 to 3.0 V around a 1.5 V reference, with roughly 1000x amplification of a +/-1.5 mV signal at the electrodes. That mid-rail offset is the trap: at rest the output sits near 1.5 V, so an ADC must be read around that offset, and a 3.3 V reference leaves about 1.5 V of headroom in either direction.
ABSOLUTE MAXIMUMS: the vendor publishes none for the output or the input, so none are quoted here.
LOGIC LEVEL: none - there is no digital interface. The analogue output is the board's own 0 to 3.0 V, which fits a 3.3 V ADC but not an ADC whose reference is below 3.0 V.
REFERENCE CIRCUIT: the vendor publishes no schematic and no pull-up, decoupling or filter values, so nothing is quoted. The three-wire Gravity cable plus the PJ-342 electrode lead is the whole connection the vendor describes.
TRAPS: the dry electrodes must be aligned with the muscle's direction and tied over a large area of bare skin or the reading drifts; DFRobot's own FAQ answers a large or unchanging reading with (1) check supply stability, (2) check electrode orientation and skin contact, (3) unplug the electrode lead and see whether the reading returns to its idle value. Operating range is 0 to 50 C.