Using Marlin's autotune on a J-head MK5B I get temperature swings of about +/- 1 C. Is this typical performance? I am sure it is adequate but a bit disappointing.
With my own firmware using bang bang I get about +/-3 C but it has much better transient response because if I say drop the temperature 20C with Marlin it winds up the I term waiting for the temperature to change and then overshoots considerably. Bang bang has no more overshoot on a temperature change than its normal oscillation.
With an aluminium heater block and the thermistor placed half way between the resistor and the barrel I can get +/-1C with bang bang.
Bang bang doesn't work well with Marlin because it doesn't sample often enough. I sample hundreds of times per second and the presence of some noise in the ADC reading then creates pseudo PWM with a small band of proportional control close to the set point.
So it seems all this extra complication doesn't actually achieve much or does anybody get better performance with PID and a MK5B?
With my own firmware using bang bang I get about +/-3 C but it has much better transient response because if I say drop the temperature 20C with Marlin it winds up the I term waiting for the temperature to change and then overshoots considerably. Bang bang has no more overshoot on a temperature change than its normal oscillation.
With an aluminium heater block and the thermistor placed half way between the resistor and the barrel I can get +/-1C with bang bang.
Bang bang doesn't work well with Marlin because it doesn't sample often enough. I sample hundreds of times per second and the presence of some noise in the ADC reading then creates pseudo PWM with a small band of proportional control close to the set point.
So it seems all this extra complication doesn't actually achieve much or does anybody get better performance with PID and a MK5B?