Precise Heating Element Control

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ekraus
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Joined: Mon Apr 23, 2012 6:37 am

Precise Heating Element Control

Post by ekraus »

Precise Heating Element Control was always a problem with the resistance controlled SSR's.The problem is that using a 5500 watt element precise control of the wattage was near impossible using a single turn pot. So I did some experimenting and built a decade control breaking the resistance into 4 pieces 100KΩ each. Even after building and using the control the wattage still fluctuates a bit due to voltage fluctuations. After building this simple control I was able to control the wattage almost perfectly.The SSR uses a 470-560KΩ POT. First thing I checked was what was the maximum resistance I needed. Came out to a little over 300kΩ so I went up to 400KΩ. The project consists of the following parts. 4-100KΩ 2W resistors, 1-100KΩ 10 Turn Pot, 3- Single pole mini switches, 1-small enclosure, assorted scrap wire. The parts were under $10.
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still_stirrin
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Re: Precise Heating Element Control

Post by still_stirrin »

So, looking at your diagram, closing the SPST switches “removes” the respective parallel resistor from the control circuit, making the current flow through the switch instead of the resistor. Opening a switch “adds” the respective 100k ohm resistor in series with your 100k ohm potentiometer.

Is this correct?

And it gives you the required sensitivity in the power ranges you’re trying to achieve? Have you used it yet?
ss

p.s. - how much was the 10-turn precision 100k ohm pot?
My LM/VM & Potstill: My build thread
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