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Temperature control circuits, despite the rise of digital technology, continue to rely on analog sensors like NTC thermistors and RTDs, which are prevalent in automotive and industrial applications due to their reliability and cost effectiveness. While digital simulation software such as SYNOPSYS Saber RD and Simulink Simscape is available for those who can afford it, they often lack precise models for passive components like thermistors. SPICE analysis, therefor, remains a mainstay for circuit analysis due to its popularity and accessibility. Recently, however, QSPICE
— a free software developed by Mike Engelhardt of LTspice® fame — has emerged. It uniquely supports digital simulations with VERILOG and C++, bridging the gap between traditional SPICE and modern digital circuit descriptions. this blog will present a complete simulation of a PID controller defined in QSPICE coupled to a Vishay NTC thermistor NTCS0603E3103FLT.
The PID controller has been separated into its 3 blocks (proportional/ differential/ integrative) and each block has been verilated separately in order to verify their functionality.
Optimization of the PID coefficients is easily performed by sweeping the values of Kd, Ki, Kp through realistic ranges and the result of temperature control can be seen hereunder.
time (s)
The offset between the oven temeprature and the set temperature prfile is now kept to a minimum.
