Action22 Posted May 29, 2022 Report Share Posted May 29, 2022 Hi, V700 with V200-18-E3XB Is it possible to have a PID only output at 0% or 100% and nothing in between? I am trying to do this to prevent a hardware component from chattering when it is not ran at 100% I see in Visilogic function block software manual it says the following I have set the proportional band to 0 but i still notice that i am getting values in between 0 and 100 . I've attached the project, any advice appreciated. 52.vlp Quote Link to comment Share on other sites More sharing options...
MVP 2022 kratmel Posted May 29, 2022 MVP 2022 Report Share Posted May 29, 2022 44 minutes ago, Action22 said: Is it possible to have a PID only output at 0% or 100% and nothing in between? It is SLOW PWM output for PID. Please use in FB's menu section PWM--> SCAN. You can find in HELP how to operate PWM (0-1000 PID output=0-1000 PWM). Then your 0-100% PID output can operate ON-OFF controlled heater. Duty Cycle for SLOW PWM must be set approx 2-40s ( for example Duty Cycle in steps of 0.25ms (400=1sec)) . Quote Link to comment Share on other sites More sharing options...
MVP 2022 kratmel Posted May 29, 2022 MVP 2022 Report Share Posted May 29, 2022 If you do not need PID control, Deadband Example.vlp sample code can be used for deadband control. Quote Link to comment Share on other sites More sharing options...
MVP 2022 Flex727 Posted May 30, 2022 MVP 2022 Report Share Posted May 30, 2022 17 hours ago, kratmel said: If you do not need PID control, Deadband Example.vlp sample code can be used for deadband control. This is probably the best answer - a basic thermostat with hysteresis. Easy to implement and 100% reliable. Quote Link to comment Share on other sites More sharing options...
Action22 Posted May 30, 2022 Author Report Share Posted May 30, 2022 Great I will give this a try, appreciate the feedback! Quote Link to comment Share on other sites More sharing options...
Action22 Posted June 9, 2022 Author Report Share Posted June 9, 2022 I did make the change, however I notices that the temp fluctuates .4 c below and .7c above the setpoint. I tried change where my deadland was set but the range would not tighten. Any advice appreciated. Quote Link to comment Share on other sites More sharing options...
MVP 2022 Joe Tauser Posted June 25, 2022 MVP 2022 Report Share Posted June 25, 2022 By definition, Deadband Control is fully on or fully off. There's no in-between, and you said in your initial post that you wanted to prevent hardware chattering. That small of a fluctuation is really quite good for deadband control. The range from deadband control can vary from +/- 1 degree to +/- 50 degrees depending on the thermal characteristics of the system. You can't have it both ways. If you want more accurate control you'll need something that can utilize a PID loop properly and apply energy to the system in an analog fashion - somewhere between 0% and 100% with a one second or faster loop update. This is what we use solid state relays for in a heating application. Joe T. Quote Link to comment Share on other sites More sharing options...
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