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PID using OPAMPS or transistors

V

Vipin Nair

Jan 1, 1970
0
Hello,
Does anyone has circuits of PID controller implementation with OP-Amps or
Transistors.
Any sample configuration is OK.

Regards
Vipin
 
J

John Popelish

Jan 1, 1970
0
Vipin said:
Hello,
Does anyone has circuits of PID controller implementation with OP-Amps or
Transistors.
Any sample configuration is OK.

Regards
Vipin

PI is very simple. you feed PV (process variable, or measured value)
or SP (setpoint) into the - input through a resistor, and the SP or PV
into the + input. The feedback from output to - input is a capacitor
in series with a resistor. This configuration produces both integral
and proportional effects on error (integral effect always takes place
on error, since its job is to bring average error to zero,
eventually). If you want to be able to move the setpoint, and have
only integral response take you to the new setpoint, you can't put
both effects in the same feedback path.

Adding derivative also involves some choices. Do you want the
derivative to act on error (setpoint and process changes) or just on
process change?

Then you start adding things like anti-windup prevention on the
integral, etc.
 
B

Ban

Jan 1, 1970
0
John said:
PI is very simple. you feed PV (process variable, or measured value)
or SP (setpoint) into the - input through a resistor, and the SP or PV
into the + input. The feedback from output to - input is a capacitor
in series with a resistor. This configuration produces both integral
and proportional effects on error (integral effect always takes place
on error, since its job is to bring average error to zero,
eventually). If you want to be able to move the setpoint, and have
only integral response take you to the new setpoint, you can't put
both effects in the same feedback path.

Adding derivative also involves some choices. Do you want the
derivative to act on error (setpoint and process changes) or just on
process change?

Then you start adding things like anti-windup prevention on the
integral, etc.


1 opamp implementation:
||Cd ___ ||Ci
.--------||-o--|___|--||-.
| || | R2 || |
in | ___ | |\ |
o--o-|___|-----o--|-\ | out
R1 | >------o--o
.-|+/
| |/
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

If you know the corner frequencies fd and fi and the required gain Ap.
Ap= - R2/R1

fi= 1/(2pi*Ci*R2)

fd=1/(2pi*Cd*R1)

This is valid for Cd/Ci<<R2/R1. It is advisable to limit the max. diff. gain
with a small resistor in series with Cd.
I can also draw an independently adjustable circuit with 4opamps if needed.
 
J

John Popelish

Jan 1, 1970
0
Ban said:
1 opamp implementation:
||Cd ___ ||Ci
.--------||-o--|___|--||-.
| || | R2 || |
in | ___ | |\ |
o--o-|___|-----o--|-\ | out
R1 | >------o--o
.-|+/
| |/
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

If you know the corner frequencies fd and fi and the required gain Ap.
Ap= - R2/R1

fi= 1/(2pi*Ci*R2)

fd=1/(2pi*Cd*R1)

This is valid for Cd/Ci<<R2/R1. It is advisable to limit the max. diff. gain
with a small resistor in series with Cd.

Yes. Typically equal to or greater than R1/10.
 
V

Vipin Nair

Jan 1, 1970
0
Hi,
Thanx for the solutions
Il build upon it.

Rgds
Vipin
 
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