0120-24 Simple PID Loop
Example Projects > 0120 Raspberry Pi > 0120-24 Simple PID Loop
Simple PID loop on Raspberry Pi
The source files illustrating the use of a simple PID controller on Raspberry Pi in REXYGEN are located in this folder.
The PIDU function block allows bumpless switching of manual and automatic modes. Toggle the CNB_MAN constant to switch the mode. Change the CNR_sp constant in automatic mode or the CNR_hv constant in manual mode and observe the controller action (mv) and the process reaction (pv).
In this example, the controlled system is a box. A process value is the temperature and it is measured by 1-Wire DS18B20 sensor. The actuator can be a heater controlled with PWM.
The signals are recorded in the TRND block which allows displaying of the trends (graphs) in the Watch mode of REXYGEN Studio or in the REXYGEN Diagnostics diagnostic tool.
Timing of the project
The algorithm runs each 100 milliseconds (0.1 s). See the EXEC function block,
tick x ntick0 = 0.01 x 10 = 0.1
- REXYGEN Runtime Core, RPiDrv and OwsDrv modules must be installed and running on the target device (Raspberry Pi).
- Owserver (part of the OWFS package) must be installed, correctly configured and running on the Raspberry Pi.
- The wiring must comply with the attached schematics.
Running the example
- The *exec.mdl file is the project main file.
- Open it with REXYGEN Studio.
- Specify the 64-bit ROM ID of the attached temperature sensor. See the 1-Wire driver manual below.
- Compile and download it to the target device.
- Switch to Watch mode and observe the algorithm (use Target->Watch selection to display data).
- Open trend diagnostic window for the block TRND.
- Change the set-point (CNR_sp) in automathic or hand-value (CNR_hv) in manual mode to 3.
- Observe the controller action (PIDU:mv) and the process reaction (OWS__temperature) in trend.
User interface (HMI)
The example is accompanied by a HTML5-based user interface built on the WebBuDi framework (Web Buttons and Displays). There is also a WebWatch HMI generated directly from REXYGEN Studio.
- Press F1 for help on the selected function block in the REXYGEN Studio.
- Getting started with REXYGEN on the Raspberry Pi minicomputer
- RPiDrv - Raspberry Pi driver (including PiFace Digital, UniPi v1.1 Intellisys PIO)
- OwsDrv - 1-Wire driver
- REXYGEN HMI User Guide
- Function blocks of REXYGEN
- REXYGEN Studio User Guide
- Complete documentation of REXYGEN