A Low-cost Optocoupler-Based Isolator System for IoT-Based Voltage Measurement in Low and High voltage DC Applications

Abstract

Internet of things (IoT) connected devices operate at extremely low voltages that are susceptible to common-mode noise and electromagnetic interference. As a result of this, integrating IoT devices with low or high-voltage direct current power sources requires galvanic isolation which is often expensive to attain. In this work, the use of a low-cost conventional optocoupler (4N35) in the galvanic isolation of an IoT voltmeter required to measure the potential difference of a low voltage direct current source with a maximum relative error of 1% was investigated and experimentally verified. The proposed isolator circuit was first simulated using NI Multism and then fabricated on a printed circuit board for experimental verification after satisfactory simulation results. Measurement results from the experimental verification process were used to fit quadratic and cubic regression equations that approximate the input signal voltage from the isolator’s output voltage measured by the IoT voltmeter. Lastly, the isolator and IoT voltmeter were connected to a variable 100-1000 VDC source via a potential divider network for performance verification at a voltage step of 100 VDC. Here, the isolator successfully achieved its primary goal of providing galvanic isolation between the voltage source and the IoT voltmeter while maintaining a maximum relative error of 1%.