Verified 2026-11
dfrobot Gravity: Analog Signal Isolator
Two-terminal analog isolator: 5.0 V in on the MCU side at 75 mA, generates an isolated 5 V for the sensor side, 0-5 V analog both ways with 4 s response and plus or minus 20 mV error, $19.90 USD.
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Part & documents
| Source | www.dfrobot.com/product-1621.html → |
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Specs
| MCU | STMicroelectronics STM8S103F3P6 |
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Pinout
6 pads, as the vendor numbers them.
| # | Name | Function | Signals |
|---|---|---|---|
| 1 | - | MCU terminal pad 1 - power input GND. | ground |
| 2 | + | MCU terminal pad 2 - power input VCC 5.0 V plus or minus 0.1 V; net +5V on the schematic. | power in |
| 3 | A | MCU terminal pad 3 - analog signal output 0-5.0 V to the host ADC; net OUT on the schematic. | analog output |
| 4 | Isolation GND | SEN terminal pad 1 - isolation power output GND (IGND on the schematic). The vendor's table prints the label as A here, contradicting its own description. | isolated ground |
| 5 | Isolation +5V | SEN terminal pad 2 - isolation power output VCC 5.0 plus or minus 0.2 V; net i5V on the schematic. The vendor's table prints the label as - here. | isolated 5 V out |
| 6 | Isolation AIN | SEN terminal pad 3 - analog signal input 0-5.0 V from the sensor. The vendor's table prints the label as A here. | analog input |
Power
| Input | 5.0 V plus or minus 0.1 V on MCU terminal pad 2 |
|---|---|
| Typical draw | 75 mA |
Notes
The vendor's six-row pinout table has a broken Label column (A, +, -, A, -, A) whose rows 4-6 disagree with their own descriptions; the entry follows the descriptions and records the disagreement rather than fixing it. The row-to-pad mapping for the SEN terminal was fixed against the schematic, whose J2 pad 2 carries the isolated i5V net, matching row 5's 'Isolation Power Output VCC'. The schematic's J1 nets are GND on pad 1, +5V on pad 2 and OUT on pad 3, matching rows 1-3.
AI context
Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.
PART: DFRobot Gravity: Analog Signal Isolator, SKU DFR0504 - a 42 x 32 mm two-sided analog isolation module. One side is the MCU terminal, the other the SEN terminal, and the two are joined by an isolated 5 V DC-DC (U2, IB0505LS-1W) and an optocoupler-based analog path around a microcontroller (U1, STM8S103F3P6) plus a 6N137S optocoupler and a TL431A reference. The vendor names no headline part in the title, so part is null. ADDRESSES: none. Both terminals are three-wire analog/power connectors, not a bus. PINOUT: six pads, numbered as the vendor's own pinout table numbers them. MCU terminal (right-hand, 'Gravity 3P Raw'): 1 -, power input GND; 2 +, power input VCC 5.0 plus or minus 0.1 V; 3 A, analog signal output 0-5.0 V. SEN terminal (left-hand, 'Gravity 3P Isolation'): 4, isolation power output GND; 5, isolation power output VCC 5.0 plus or minus 0.2 V; 6, analog signal input 0-5.0 V. SUPPLY: 5.0 V on the MCU side (1.0 V tolerance 0.1 V), no-load current 75 mA. The isolated side is generated by the module at 5.0 plus or minus 0.2 V and must not be fed from the host. LOGIC: there is no digital signal anywhere - both terminals carry a 0-5.0 V analog voltage and the module's own rail. Do not exceed 5.0 V on either analog pin. CIRCUIT: the vendor publishes the schematic. J1 is the 'Gravity 3P Raw' MCU-side connector with pad 1 on GND, pad 2 on +5V and pad 3 on the OUT net, i.e. the module's analog output; J2 is the 'Gravity 3P Isolation' SEN-side connector with pad 2 on the isolated i5V rail. The isolated 5 V comes from U2 (IB0505LS-1W) and is filtered by C3 4.7 uF and C8 100 nF; the MCU side carries C1 4.7 uF and C2 100 nF on +5V and 10 kOhm resistors R1/R2/R3/R4/R5 on the analog and control nodes, one of them divided by R25 100K and R4 2K into the STM8's ADC, with a TL431A as the 2.495 V reference. TRAPS: (1) The vendor's pinout table contradicts itself: the Label column prints A, +, -, A, -, A for the six rows while the Description column calls rows 4, 5 and 6 'Isolation Power Output GND', 'Isolation Power Output VCC' and 'Analog Signal Input' - the second connector's labels are wrong in the table, and this entry follows the descriptions (row 5 is the isolated supply, which the schematic confirms by tying J2 pad 2 to the i5V net). (2) The prose then says the LEFT connector is SEN and the RIGHT is MCU, while the table lists the MCU rows first - wire by the terminal names, not by the row order. (3) The response time is 4 seconds typical, so a fast sensor is not suitable. (4) Analog error between the two terminals is plus or minus 20 mV typical, which is the net accuracy you lose for the isolation.
Provenance
Every figure on this page was read from the 3 sources below and last checked on Nov 2, 2026.