Low-Cost Method to Detect 240VAC 50A Heating Element Open Circuit Failure

The discussion addresses low-cost methods to detect open circuit failure in 240VAC 50A heating elements by sensing when current drops near zero. Suggested solutions include using simple analog or digital ammeters for direct current measurement. A preferred approach involves employing current transformers (CTs) with a single primary turn (the heater wire) passing through a toroidal core and a high-turn secondary winding. The CT secondary is loaded with a burden resistor to produce a measurable voltage proportional to current. This voltage can be rectified and fed to a microcontroller input for a binary on/off indication without complex RMS conversion. Safety isolation is inherent in CTs, preventing high voltage from reaching the PCB. PCB-mounted current sense transformers like the CST206-1A (110A rated) are recommended, with a burden resistor typically around 47 ohms, adjustable up to 100 ohms per datasheet guidelines. Alternative sensing technologies include Hall effect sensors (e.g., Allegro Microsystems, LEM, AsahiKasei CZ-3700) and anisotropic magneto-resistive sensors (e.g., Aceinna MCA1101), which provide isolated analog outputs suitable for integration. Ready-made current transducer modules from Phoenix Contact and Weidmuller offer plug-and-play solutions with analog outputs and limit detection features. For interfacing, microcontrollers controlling the heater can use the sensor input to detect heater status reliably. Additional suggestions include using LEDs across the CT secondary for simple visual indication and ensuring the CT secondary is never left open-circuited to avoid damage.
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