Isolated Analog Control with Potentiometer

This is an Isolated Potentiometer Module that integrades an LOC110 linear optocoupler, isolated DC-DC converter, an onboard 10K linear potentiometer, and supporting circuitry. This module is designed for reliable operation in VFD drives, process control, PLCs, automation, and other industrial applications where safe analog signal isolation is required.

Thanks to the onboard isolated DC-DC converter, the module operates from a single 5V DC supply, simplifying integration. With full rotation of the potentiometer, the output provides a 0–3.3V DC isolated analog signal, completely isolated from the potentiometer input.

The design is based on the LOC110 linear optocoupler, which provides 3750V isolation. The MCP6001 op-amp (U2) operates as a closed-loop servomechanism, sensing the photodiode current and driving the optocoupler’s LED to maintain accurate linearity. The second MCP6001 (U3) conditions the output from the phototransistor. An onboard power LED (D1) indicates active input-side supply.

The LOC110 contains an infrared LED optically coupled with two photodiodes. The feedback photodiode stabilizes LED current, compensating for LED nonlinearity, time, and temperature variations, while the output photodiode delivers a highly linear, isolated analog signal. This architecture provides wide bandwidth, high input-to-output isolation, and excellent servo linearity.

Features

• Single 5V DC supply operation
• Onboard 10K linear potentiometer
• Integrated isolated DC-DC converter
• Power status LED indicator
• 0–3.3V DC isolated output
• Compact PCB: 47.15 × 35.08 mm

Connections

• CN1, Pin 1 = VCC (5V DC), Pin 2 = Isolated 0–3.3V Output, Pin 3 = GND
• D1 = Power LED
• R9 = Potentiometer

Schematic

Parts List

Connections

Gerber View

Photos

LOC110 Datasheet