1 Topic by electricmonk9

  • electricmonk9
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  • Registered: 2013-10-21
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Topic: PID LED clicking on and off

I just put my kit together and I'm experiencing a problem.  When I set the PID to heat to, say, 190, it'll heat to around ~175 before the heating LED (I think that's what it means, the manual was pretty confusing) will cut out.  After a few seconds it'll pop back on and the cycle repeats.  The result is the heat sort of goes up and down and only very, very slowly creeps up.  Anyone know what could be causing this?

2 Reply by elmoret

  • elmoret
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Re: PID LED clicking on and off

That is the entire point of a PID controller. It is normal. It will respond faster once autotuned.

http://en.wikipedia.org/wiki/PID_controller

What you're seeing is the effect of the (D)erivative portion. After auto tuning, this gain will be automatically set to an appropriate level for the thermal properties of the system.

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3 Reply by electricmonk9

  • electricmonk9
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Re: PID LED clicking on and off

Thanks, sorry to be such a dingus.

4 Reply by laird

  • laird
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  • Registered: 2013-08-28
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Re: PID LED clicking on and off

elmoret wrote:

That is the entire point of a PID controller. It is normal. It will respond faster once autotuned.

http://en.wikipedia.org/wiki/PID_controller

What you're seeing is the effect of the (D)erivative portion. After auto tuning, this gain will be automatically set to an appropriate level for the thermal properties of the system.

Very interesting article. I had no idea that PID controllers had such deep math behind them - I kinda thought they were just a simple control of a relay controlling an input (heater) based on the sensor (temp) being below or above the setpoint. It's amazing that the guy who did the math did it all on paper, with ships.