PID control for HP Vee


Thread Starter


currently working on a project to control the humidity of a room, using HP Vee to monitor the status at the room. when the humidity drops,
the HP Vee will energised a relay which control the on/off of a water mist injector. due to the large lag the humidity fluctuate. therefore,
PID control to be introduced to contol the humidity.

Would appreacite anyone can help me how to implement the PID control using the HP vee and any similar program can be e-mail to me.
From your message I can probably conclude that the water mist injector you use can operate only in on/off mode (if it's not the case you can apply PID control directly controlling water supply to the injector). It leaves to the
PID control the only option that is an application of pulse width modulation (PWM). To implement it along with the PID strategy you need:

1. to determine an acceptable cycle period time T. A proper choice would be about 0.1 of the dominant time constant of the process you control. In your case this time can be estimated as the time required for the humidity to settle
after injection. Thus, T should be 0.1 of the former.

2. After that you need to establish a relationship (and program it) between the output of your PID control and the required ON/OFF ratio of the PWM control.
For example, if the output range of the PID controller is ['100%;100%] then 0 'ON/OFF ratio' corresponds to '100% of PID output, 0.5 corresponds to 0% of PID and 1.0 corresponds to 100% of PID.

3. Program the above strategy, so that, for example, 0.3 'ON/OFF ratio' means that the injector is ON during the time 0.3T and OFF during the time 0.7T, etc. 4. The rest of the design doesn't differ from an ordinary PID control.

Dr. Igor Boiko
Consulting in Control is available
(including modeling, simulations and control design)
[email protected]
Tel: 1-403-294-2745
my name is Alessandro from Italy.
i use hpvee 4.0 for irrigation system with suspended undercarriages.
There are 12 undercarriages everyone slides for 100 meters, controlled by hpvee 4.0