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Heater to remain on after a period of time of the set temperature is reached to avoid turning on and off repeatedly.

 

Hello,

 

I have a problem, i have a heater (represented by an LED light) that activates when the temperature i am recording reaches 2 degrees C. However i am finding that if the temperature stays around this temperature the heater flickers on and off, however this would damage equipment in real life.

 

Can anyone supply a solution to make the heater remain on for an extra set amount of time?

 

MBlair1234_0-1609624904960.png

 

 

This is for a university assignment, i'm very new to LabVIEW!

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Message 1 of 4
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The thing you are looking for is called hysteresis. Basically it means that you have different on and off thresholds.

 

In the picture you can see that the heater only turns off after crossing the high threshold and only turns on again after it goes below the low threshold. If it goes under the high threshold but not the low one then the heater stays on.

 

switching-fuction-window.jpg

 

There's an example in this thread:

https://forums.ni.com/t5/Multifunction-DAQ/hysteresis-bang-bang-control-for-thermostat-in-cDAQ/td-p/...

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You have attached a VI that looks quite different to the image you show. So which one is correct?

 

Please adapt some of my ideas posted here instead of that bewildering mix of feedback nodes and shift registers.

 

There I already showed you how to do timing, so you should be able to adapt that for the new purpose. Basically, if the ON and OFF time should be a defined nonzero duration just start timing when the state changes and force it to remain for the given duration. Should not be too hard. Of course you probably want to do some built-in safety so it turns off more quickly if the temperature gets way too high, for example.

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Are you sure this activity would damage the equipment?  If this is a temperature chamber, the equipment is designed to work this way.

Bill
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