Hi Bert,
With a bit of searching I came across the following:
http://www.anale-ing.uem.ro/2009/2009_a9.pdf
It is a nice simple example of a PID controller.
When looking on Figure 1.b you will see the schematic.
This schematic has 5 different parts:
- Voltage Follower: This allows you to uncouple the rest of the circuit from the input, making sure you don't distort the input error signal. (Amplifier with gain 1)
http://www.electronics-tutorials.ws/opamp/op-amp-building-blocks.html
- Proportional: This is the P part of your PID controller. The P factor is the gain of this inverting amplifier.
http://www.electronics-tutorials.ws/opamp/opamp_8.html
- Integrator: This is the I part of your PID controller. The I factor is dependent on both the capacitance and resistance.
http://www.electronics-tutorials.ws/opamp/opamp_6.html
- Differentiation: This is the D part of your PID controller. The P factor is also dependent on both the capacitance and resistance.
http://www.electronics-tutorials.ws/opamp/opamp_7.html
- Addition: This will merge all the correcting signals from the P, I and D component with a certain gain.
http://www.electronics-tutorials.ws/opamp/opamp_4.html
Please keep in mind that the input is the error signal. To get this signal you need to subtract the desired value from the actual value.
Have a look at the following:
http://www.electronics-tutorials.ws/opamp/opamp_5.html
Lastly I made the following example:
https://www.multisim.com/content/bFq4rZYn2YGh9Yggo2McnA/pid-control/
(You may want to switch around the reference and input temperature depending if you have a positive or negative feedback)
This should be enough to allow you to create your PID controller 🙂
Kind regards,
Natan Biesmans