Hello I am currently working on a project using an Arduino Uno, 1500 W immersion heating element from mcmastercarr, and PT100 RTD temperature sensor. I am wanting to read in the temperature from the PT100 to the Arduino, and based on the reading control the heating element. I am looking to control the temperature of around three gallons of water for upwards of an hour with a +/- .5 F precision. I currently have a mechanical relay that can control the on/off of the heating element. However, I am not sure whether or not I be able to control the element enough with a simple on/off tactic. I am considering a couple of options:
1. First, I realize that the mechanical relay will need to be replaced with a Solid State Relay because of the amount of switches that will occur per use. But if I had a SSR, I am thinking of trying to tinker with an equation to program into the micro-controller that will be able to control the on/off to desired precision. Something like as the temp nears the desired temp, i.e. within 10 F of 150 F, cycle on 10 seconds and off one second, and them within 9 F a different cycle. The SSR shouldn't have any problem handling this amount of switches, or so I have read. Or does anyone have any experience using the Arduino PID library?
2. I am also considering using a TRIAC. Kind of like the way a light dimmer works, but with a longer period because the heating is a lot slower process. It is my understanding that a TRIAC can be used like a relay, only the output can be controlled based on the input into the TRIAC that can be controlled by the micro-controller. So maybe something like lower the output as it gets within X degrees of the desired. Then simply use the on/off without cycling but just at a lower percent.
Any comments, concerns, or improvements on these two approaches would be greatly appreciated. Also if anyone has a different/better idea as to do this I am definitely open. Thanks in advance to any responses.
1. First, I realize that the mechanical relay will need to be replaced with a Solid State Relay because of the amount of switches that will occur per use. But if I had a SSR, I am thinking of trying to tinker with an equation to program into the micro-controller that will be able to control the on/off to desired precision. Something like as the temp nears the desired temp, i.e. within 10 F of 150 F, cycle on 10 seconds and off one second, and them within 9 F a different cycle. The SSR shouldn't have any problem handling this amount of switches, or so I have read. Or does anyone have any experience using the Arduino PID library?
2. I am also considering using a TRIAC. Kind of like the way a light dimmer works, but with a longer period because the heating is a lot slower process. It is my understanding that a TRIAC can be used like a relay, only the output can be controlled based on the input into the TRIAC that can be controlled by the micro-controller. So maybe something like lower the output as it gets within X degrees of the desired. Then simply use the on/off without cycling but just at a lower percent.
Any comments, concerns, or improvements on these two approaches would be greatly appreciated. Also if anyone has a different/better idea as to do this I am definitely open. Thanks in advance to any responses.