Realizing Positive Temperature Co-efficient of Resistance Effect using an IC-555 Timer Circuit

K. M. Anand, J. Mukherjee and K. Prasad

T.M. Bhagalpur University, Bhagalpur

In this paper, a simple yet effective and alternative method is described to observe the temperature dependence of resistance of a positive temperature coefficient of resistance (PTCR) by making use of a free-running multivibrator constructed around IC-555 Timer. Since the output pulse width of a free-running multivibrator is a function of the capacitances and the resistances attached to the circuit, this property along with the fact that resistance varies with the temperature to which the component is subjected can be exploited to study the variation of resistance along with the temperature. The width of the output pulse and resistance was found to increase with the rise in temperature. Hence, the circuit could be utilized for temperature sensing applications. Furthermore, this method may also be used to determine the value of an unknown resistance R(T) attached to the circuit and the value of the temperature coefficient of resistance (α). This simple and cost-effective method could be included as an experiment in the curriculum of various undergraduate and/or post-graduate courses and can also be taken upon as a project work by interested students.