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“This is one of the most interesting and hardest experiment to do, Why?because the circuit we want to build is a little bit hard and tricky. Most of the tutorial in the internet do it with relay to turn on-off the AC heater to increase the temperature,it’s not an accurate way to control the water temperature,and will not be able to reach to your target temperature. To explain it in a simple example: you want to increase a temperature of the water to be about 60 degree Celsius,With a relay when you reach to 60 degree Celsius,the relay turn off the Heater, that makes the temperature decrease rapidly so the relay will turn on and increase temperature rapidly again , so the relay will turn on-off within a short time which will damage the relay and maybe damage the heater it self. Best way to adjust the temperature by control AC voltage output applied on AC heater. build a (crappy) AC triac circuit not just unprofessional but also will not work well,With inappropriate heatsink,no protection from ac short circuit or overload current, and most important no protection for you,any small fault might kill you,be careful. So let’s see the best way to control AC heater, and offer a high protection from electrical shock hazard,and give us a full control over the water temperature.”

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