Now, I am writing the final update though I really do not want to write it at this stage. But somehow I have to do it by tonight. My internet service pack will be over by 12 midnight and I have to recharge. I may not have the facility tomorrow.
- Objective of the project:
To control the oven parameters e.g. temperature, pressure with PID type of control. Selection of the parameter depends upon the availability of the sensor and ease of actuation. PID will be tried both in software and hardware.
As temperature sensors are easily available in the market temperature control will be tried. Control will be done at around 45 degree centigrade. One application is: Post-baking of photo resist in silicon processing. Many R&D labs do not have the auto-control facility. In this project, an automated, low-cost, low-power solution using PSOC4 will be provided.
- What has been achieved so far?
- Ø PID control has been implemented.
- Ø The variables in the program have been studied with i2c and idac.
- Ø Implementation of blinking LED while control takes place. LED goes off when the set-point temperature is achieved.
- Ø Use of deep-sleep mode when the control is not needed.
- Ø User interface for set-point temperature and heating supply on-off switch.
- What is left?
- Ø PID control in hardware using op-amps. This is not fully implemented as this does not give any advantage over software PID in terms of speed, cost, complexity, and power consumption. On-chip op-amps are with single supply. Implementation needs dual supply and at-least 3 op-amps. Combination of hardware and software requires frequent time consuming AD conversions. On the other hand PID program in ARM cortex is very fast and smooth.
- Ø Control is done at a much lower temperature than the proposed 45 degree centigrade. Due to non-availability of heating coil an electric bulb was used. The environment could be heated only to a temperature close to ambient. Power saving is an important aspect as the whole system is battery operated. Battery operation was planned in the very beginning for safety and ease of demonstration. As different countries have different standards for line supplies the design of heating circuitry in India may or may not work in another country.
- What will be done?
The circuit was implemented on bread-board. The PCB soldering work is to be completed. Then some results will be collected.
- How does it look?
Two card-board boxes were used. With this drilling could be avoided. Please ignore the write-ups (except the texts in black) on the boxes. In yellow room such boxes are not allowed due to the high dust count. A metallic oven as shown in the picture below is required. But basic algorithm implementation remains the same.
- PSOC4 features
Working with PSOC4 is really an amazing experience. It is so powerful and so many alternate paths are available for this implementation. Port connection is very user friendly as compared to other micro-controllers available in the market. Still I wish to have some more features in PSOC4 or a future version.
- Ø More number of op-amps with the provision to give a negative supply.
- Ø Availability of off-chip components. This will greatly reduce the power consumption, complexity, speed and cost of an application.
- Ø Alternate net-list creation in the program. Presently, connection of the various components can be done only in the GUI. GUI was a big fun in the beginning. But I prefer to code for a complex circuit with too many connections. The other great advantage of net-list is: re-connection can be done while the program runs.
- I acknowledge
I deeply acknowledge the organizers for their constant encouragement and support. Thanks a lot for providing me the PSOC kit. Because of this challenge I put my hands on PSOC4 and really loved the product. While working, I have got some interesting ideas. I shall be implementing those on PSOC4 / 3. I also want to thank PES Group of Institutions, the organization where I work, for providing me an encouraging environment to execute this work.