DeadTime control bed too hot?
Is there anyway to adjust the dead time control so that the power to the heating element is not cycled as quickly or the on time is less or limited?
I have a relay driver 110v heater in a large mass AL plate...this is great for making even heat and heats reasonable fast.
I calculate based on the Repetier instructions the dead time is about 50 seconds.
However what I find is even with long dead time the heater cycled every 10 seconds or so and stays on for a few seconds or longer even after
the thermistor reports the bed temp is over the set point. Presumably the firmware thinks the temp is dropping and is trying to catch it up before it goes too far below the set point.
What happens is I set the bed for 70 degrees the heater comes on full and stays on until the bed reaches about 50, it then cycles quickly on and off as the bed reaches 70, however it then continues to cycle as the bed passes 70 and goes to about 73 or 74 but then never sinks back to 70 but remains at the higher temp and keeps cycling on and off.
Now normally this would not be a problem but what I find is because the bed cools slowly which I like it often doesn't get below 70 before I am ready to start the next print. If the next print again sets the bed to 70 the print will never start as the bed stays at 73 and never enters the sweet spot I have set +_2 degrees. I could widen the tolerance to +-3 or 4 and that might do it, but then the print may also start at 66 which is a bit cool for the first layer. I could also try to set the last layer of the first print to something like 65 so that the bed can cool as the print finishes but most prints don't last that long and I don't want detachment during the last few layers (probably not a problem).
A better solution would be that the dead time have some sort of adjustment, maybe even self adjustment as it observes the temp never reaches or drops below the set point, or some method to reduce the time it spends on.....kinda back to a PWM style control I guess...
Maybe I missed a setting?
Any suggestion how to get and keep a stable lower temp or maybe one that bounces from 69-71 with this type of setup?
PID won't work since I use a relay setup correct?
Bang Bang might be the way but I recall some issue that pushed me to try the dead time...
And dead time has been good a little warmer than the set point but not a problem it is just not ideal
in my current print clear and print again process.