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temperature controlled water system

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kulachi

New Member
hey i want help to start a roject i m doing
in this project the temperature in the water is maintained upto its desired value in a vessel
can anyone help me with the sensors and comparators or give the links to the circuit diagram
thanx
 

KMoffett

Well-Known Member
kulachi,

Is this a class work project? If so do you have any list of resources (parts) or limitations?

If not a class work project, can you give us more details: volume of water, temp range, power source, range of control, indicators...?

Google: temperature control circuit

Ken
 

Willbe

New Member
You want bang-bang or proportional control?
 

kulachi

New Member
thanx for 4 ur replies
KMoffett
this is my class project there are no limitations
but as this is a project of feedback control systems so i must have to use feedback in any case and so far as resources are concerned just the basic circuit for the lab project
and the parts which are easily available in the market
 

kulachi

New Member
please guys i need some help over here
i have posted all the resources of the project
i just want a simple schemetic
 

kulachi

New Member
the compltete description of the project is as follows

Temperature Control System
Objective: To implement a control mechanism that regulates the temperature of water contained in a vessel.
we have to use temperature sensors which will detect any change in the temperature of the water if the temperature is higher than the desired value it should cool down the water with some variable resistor and the power source of the project will be the dc source also the temperature we r maintaining is 25 centigrade
 

ericgibbs

Well-Known Member
Most Helpful Member
the compltete description of the project is as follows

Temperature Control System
Objective: To implement a control mechanism that regulates the temperature of water contained in a vessel.
we have to use temperature sensors which will detect any change in the temperature of the water if the temperature is higher than the desired value it should cool down the water with some variable resistor and the power source of the project will be the dc source also the temperature we r maintaining is 25 centigrade

hi,
Can you get LM393 comparator ic at your location.? also thermistors.
 

KMoffett

Well-Known Member
...Temperature Control System
... if the temperature is higher than the desired value it should ...maintaining is 25 centigrade

So, the goal is the maintain the water slightly above "room temperature" (in some parts of the world). One of the problems you will encounter is "overshoot". Even though your sensor and control detects 20°C as it heats, shutting off the heater does not immediately stop the heating process. This will require cooling. Is the container metal? This provides a lot of heat loose, so the overshoot may be minimal, otherwise you will have to provide a method of cooling, to balance out the heating. Lab water-bath controllers often use a constant cooling system (think refrigeration), and add heat to maintain control near room temp. And I don't know what you mean by: "cool down the water with some variable resistor". Resistors produce heat.

In a simple system, the overshoot can be somewhat worked out be setting the temperature control below the 25°C point and "tweeking" it as it approaches the desired temp.

Also, you may want to investigate the differences between ON-OFF ("bang-bang"), PWM (pulse width modulation), and PID (proportional/integrating/differentiation) control circuits. These are in ascending order of complexity.

Ken
 

kulachi

New Member
thanx 4 replying
ericgibbs
yesi can have the comparator and the thermistor here
and the refigeration thng not to be implemented the design have in mind that i have a high power dissipation resistor placed in the water and if the temperature of the water rises then the resistor col down and this could be done with varying the current inversely with the temperature the word cool down by resistor meant that let the liquid cool down on its own i mean not heat the liquid anymore tell me if my thinking is correct and help me out with this
regards
 

pc88

New Member
Looking at how an aquarium heaters is designed might give you some ideas. The one I got from a local pet strore is very simple - just a resistor, capacitor, neon bulb, heating element and a bent strip of copper. It's so simple you can figure out the entire circuit by just looking at it.

Here's a pic of what I'm talking about: Therma-Flow Aquarium Heater

and here's a schematic (page 4 of patent): Aquarium heater - Google Patents
 
Last edited:

KMoffett

Well-Known Member
thanx 4 replying
ericgibbs
yesi can have the comparator and the thermistor here
and the refigeration thng not to be implemented the design have in mind that i have a high power dissipation resistor placed in the water and if the temperature of the water rises then the resistor col down and this could be done with varying the current inversely with the temperature the word cool down by resistor meant that let the liquid cool down on its own i mean not heat the liquid anymore tell me if my thinking is correct and help me out with this
regards


If this is the case than the circuit I suggested earlier:
https://ourworld.compuserve.com/homepages/Bill_Bowden/page2.htm#therm.gif
should do exactly what you want. The relay on the right would be used to switch power on and off to your resistor.

Ken
 
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