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Current Sensor Using an NTC (MEC202E)

This circuit was included in my book Robotics, Mechatronics and Artificial Intelligence (sold out) published in the United States. It shows how to implement a current sensor using a NTC. Applications include mechatronics or robotics projects with microcontrollers or as a building block for simple projects.

The circuit shown in Figure 1 can be used to sense the current across a circuit without making electric contact. The nicrome wire is placed near an NTC inside a small enclosure.

 When the temperature of the wire rises due the amount of current across it, the NTC senses the changes and can act on the circuit. This circuit can be used to trigger a protective circuit when a dc motor is stalled by an obstacle it has encountered, thereby avoiding overload problems.

 

Figure 1 - Current sensor
Figure 1 - Current sensor