I´m designing a ceramic kiln controller with PID function but I don´t know which values are Kp, Kd and Ki or how to calculate them. Anybody could help me? .Thanks
Why? Simple on-off control works pretty well in most cases.
For a kiln on/off may well do the job well enough.
Setting the terms in a PID loop is done by tuning, in your case on the actual kiln - you cannot give terms and calculating is impossible as you won’t know things such as loop gain for the system.
You need to understand how PID works ( Google is your friend) and how to tune it ( google) -typically this is done with the the integral. Depending on your algorithm sone times the integral term is multiplied by the proportinal term so adjustments to P may affect I !!! Eeek !
And derivative terms off , setting the prop band first. It takes a bit of fiddling and experience to master this black art. Pick a value for kp out of the air and see what happens - adjust to get a stable reading ( it may over shoot and end up away from your set point). Slowly add integral to then get to your setpoint . Derivative , you probably don’t need and comes into its own on fast responding systems where you need to slow down the rate of approaching your setpoint .