construction of a temperture controller that keep the temp. of liquid constant btw 50celsius to 80?

Question

How can i construct an automatic temperture controller that keeps the temp. of liquid constant btw 50celsius to 80.celsius. This is project i need to submit in two weeks.pls explain in details.

Answer 1

A practical implementation is to commission a PID (proportional, integral, and derivative) control system, then tune it to empirically model the actual heat source and heat sink gradient and boundary conditions against your process material’s specific heat, thermal conductivity, and any agitation factor.

Read the current temperature difference between your sensor and your target that is your proportional error, Ep.

Read the average of the temperature during the last minutes or hour, it is your integral error, Ei.

Read the rate of change of the temperature, maybe fraction of degree per minute or per hour, it is your derivative error, Ed.

Then make the control adjustment as
SetPointChange = Sp * Ep + Si * Ei + Sd * Ed.

Where SetPointChange is the temperature delta to change to command to your heat source processor. And Sp, Si, and Sd are sensitivity factors due to proportional, integral, and derivative error, respectively.

You then experiment with your controller by injecting step changes in the set point target.

For each step change, you first tune Sp to shorten the response’s rise time to a point that the overshoot is affordable.

Then you tune Sd to minimize the overshoot.

Then you tune Si to get rid of any steady state error between your target set point and the sensor temperature.

You only need to do the tuning once for each combined system configuration of heat source, heat sink, and the specific heat, thermal conductivity, and agitation factor of your liquid production material.

Good luck!

Answer 2

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Answer 3

You call a 30°C range *constant*??? ☺

Get a thermal switch that opens at about 70°C and wire it in series with a heating element. Since I have no idea how much liquid you are working with, I have no way of guessing how large the heater should be or what the current carrying capacity of the switch should be.

Drop a line and let me know a few details and I can be of a *lot* more help ☺


Doug

Answer 4

you can use a microprocessor or micro-controller based temperature controller
say 8085,8086 microprocessor is good enough
you need a thermo couple
you also need to design an analog to digital converter using a 0809 ADC chip
use a parallel port to connect to your computer
then write a program
i know i am sounding simple you can check it out on electronics for you or some ADC books