PID Controllers - Arduino - page 133

The ON/OFF controller is much like the DEAD BAND controller, but uses only a single setpoint. When the input
is below the value, the output is turned on, and then it is turned off when above the setpoint.
Figure 7-2 is the graph of a PID using the RC filter; the gains are equal to .5 for this particular tuning and setup.
There is a slight overshoot produced, but the system quickly reaches a steady state, with an approximate steady-state
error of +/-4. This is normal for the noise produced in the system.
Figure 7-2. A graph of a PID setup with an RC low-pass filter
Figure 7-3 demonstrates an ON/OFF controller that has a higher rise and a slower fall per program step; this
simulates how an thermostat might work. This controller is set up with the same components as Figure 7-2 , just using
different code. One of the biggest comparisons between the ON/OFF and the PID is the steady state contains much
more disturbance and there is no direct control on how long the system will stay at the setpoint.