Multipurpose Analog PID
Controller
Todd P. Meyrath1
Atom Optics Laboratory
Center for Nonlinear Dynamics
University of Texas at Austin
°c 2005
March 14, 2005
revised December 10, 2005
See disclaimer2
This analog circuit is intended to be used as a multipurpose PID controller. The
schematic and PCB given here may be setup to be used as a logarithmic laser intensity
controller, laser diode current controller up to 1/2 Amp directly, temperature con-
troller, controller for high current device, etc... These configurations depend on which
options are used, and in some cases, what external devices to which it is interfaced.
The layout was intended to be flexible so that it can accommodate many different
possibilities. I hate redesigning the same circuit for various applications. Most likely I
have forgotten many possibilities, but using the simple voltage sense and voltage con-
trol output, the circuit should be useful for many applications assuming appropriate
external components are used.
There are several options for setpoint input, sense return, and output drive. The
PID may be operated using a single opamp, or a multiple opamp setup. These are
standard configurations, the former has the advantage of fewer components but has
coupled PID characteristics. The latter has independent PID characteristics so they
may be optimized independently. The setpoint circuit includes options for an analog
input, a potentiometer or trimpot offset adjust, a gain or inversion option. The sense
possibilities include a voltage/current sense, high current sense, direct output current
sense, or a logarithmic photodiode sense. The output stage may be set up to drive up
to 1/2 Amp of current either as a control single or directly driven current controller.
The circuit requires a dual ±15 V supply.
As mentioned, the circuit my be set to use single or multiple opamp PID, use the
single or the multiple opamp PID hook-up as in the table:
1
Please send comments, questions, corrections, insults to meyrath@physics.utexas.edu
2
Disclaimer: The author provides this and other designs on the web as a courtesy. There is no
guarantee on this or any other designs presented, use at your own risk. The author also comments
that the suggested parts used are not an endorsement of any manufacturer or distributer.
1
Single OpAmp PID hook-up
Use C1 to C3, R1 to R4, U1, U2
Omit C4 to C6, R5 to R9, R11, R12, U3 to U5
a
Short R10, R13
Proportional Gain (R1 + R2)/R3
Integration time R3 × C2
Differentiation time (R1 + R2) × C3
Notes: R4 limits differential gain, C1 gives high frequency roll-off.
Multiple OpAmp PID hook-up
Use R1 to R3, R5 to R9, (R10 to R13 = 1 kΩ)
C2, C4 to C6, U1 to U5
Omit C1, C3, R4
a
Short C2
Proportional Gain (R1 + R2)/R3
Integration time (R5 + R6) × C4
Differentiation time (R7 + R8) × C5
Notes: R9 limits differential gain, C6 gives high frequency roll-off.
a
use a 0 Ω resistor, 1206 package.
The summer used for the multiple opamp PID is an inverting summer, in some
cases, it is desired to re-invert the signal. Use as in the table:
Output inverter option used
Use R14, R15 = 1 kΩ, U6
Output inverter option not used
Omit U6
Shorta R14, R15
a
use a 0 Ω resistor, 1206 package.
The circuit is naturally bi-polar, however, some cases require a un-polar output.
Use the simple diode rectifier as in the table:
Output rectifier option used
For positive output only, use R17 = 10 kΩ, D1
For negative output only, use R17 = 10 kΩ, D1 (reverse diode
direction drawn on schematic and layout)
omit R61 in either case.
Output rectifier option not used
Omit R17
a
Short R61
a
use a 0 Ω resistor, 1206 package.
By convention, we will not list decoupling capacitors to be omitted when the
associated IC is listed. The associations are given on the table:
2
Supply decoupling caps associated with ICs
IC Capacitors Value
U1 C10,C11 0.1 µF
U2 C12,C13 0.1 µF
U3 C14,C15 0.1 µF
U4 C16,C17 0.1 µF
U5 C18,C19 0.1 µF
U6 C20,C21 0.1 µF
U7 C8 0.1 µF
U8 C22,C23 0.1 µF
U9 C24,C25 0.1 µF
U10/U11 C26,C27 0.1 µF
U10/U11 C28,C29 10 µF
There are a number of setups for the setpoint, most are summarized in the table
here, but the user can have some imagination and come up with others:
Setpoint Options
Option Instructions
Analog input only Use: J1, D2, R22
Short: R18, R57
Omit: R19 to R21, R23 to R35, R58, R59
D3, D4, C9, C34, C35, U9
Potentiometer input Use: R28 or R35 (trimpot or potentiometer),
(zero adjust) only R26, R27, R29, R30, C9, C34, C35, D3, D4
Short: R21, R57, (R31 and R34) ora (R32 and R33)
Omit: J1, D2, R18 to R20, R22 to R25, U9
Analog input with zero adjust Use: J1, D2, R22, R28 or R35 (trimpot or potentiometer),
R26, R27, R29, R30, C9, C34, C35, D3, D4, U9
Short: (R18 and R20) orb (R19 and R21) and
(R31 and R34) ora (R32 and R33)
add in gain adjust when using U9, use R23 to R25,
50 kΩ
the gain is 1 + R23+R24+R25
b
Invert setpoint signal Short: (R18 and R20) or (R19 and R21) omit other 2,
remember that pin 3 of U9 is non-inverting and pin 2
is inverting.
Unipolar zero adjust (short R58, omit R26, D3, C34) or
(short R59, omit R30, D4, C35)
use R27 or R29 as 0 Ω as appropriate.
a
Potentiometer direction Short: (R31 and R34) or (R32 and R33) omit other 2,
the direction of increase depends on if it is hooked to
the inverting or non-inverting pin of U9.
The several sense options are summarized in the table. The photodiode uses a
logarithmic amplifier so that it may operate over many orders of magnitude. The other
3
options are all really the same thing depending on interpretation. The current/voltage
sense uses either a ‘sense’ or load resistor from a current or voltage source. R46 is
included for the option of breaking the ground connection or adding additional load to
the driving sensor. This option would be used for instance in a high current controller
where a hall sensor is used. Another version is a high current sense using R47,
the PCB is setup for an SR20 2 Watt 4-point sense resistor (Caddock Electronics).
Depending on the resistance used, this resistor can directly measure up to 15 Amps.
An additional current sense that can be used is a direct output measurement. In this
case, there is no control output signal, and the buf ICs directly supply up to 1/2 Amp
to a load. In this low current driver mode, no external components are needed. For
the higher current cases, a high power output stage is needed, and is controlled with
the control output signal.
Sense options
Photodiode Use: R36 to R39, (R56 or R60), C0, C7, C8, U7
Short: R40
Omit: J3, R41, R42 to R47, R54, U8
Current/voltage sense Use: J3, R42 to R46, U8
Short: R41
Omit: R40, R36 to R39, R47, R56, R60, C0, C7, C8, U7
High current sense Use: R42 to R44, R47, U8
Short: R41
Omit: J3, R40, R36 to R39, R45, R46, R56, R60, C0, C7, C8, U7
connect up to 15 A (depending on R47 value) through J5 to J6
Direct output current sense Same as high current sense, but short R54, omit R55,
for use with the buffer output stage.
connect load across J6 to J7.
For the BNC connectors, the board is setup to accept either the right angle re-
ceptacle (227222-1) or the vertical receptacle (227161-1). The vertical receptacle my
be mounted on the top or the bottom of the board.
The author would like to thank Gabriel Price for testing out the multiple opamp
PID and his ideas with this, and also the suggestions and comments of Florian Schreck
and Hrishikesh Kelkar. For pointing out typos thanks to Jonathan Hayes.
4
Figure 1: A board set up for a laser intensity control circuit.
5
Power Supply Connections
+15V
Multipurpose Analog PID Controller 8
LM78L12M
1
+12V
R57
External Power Connections
C41 C36 U12
Todd Meyrath Version 1.0 470µF 10µF
Atom Optics Laboratory March 15, 2005 2-3, 6-7
Analog Control + + + C38
Input R22 D5
Center for Nonlinear Dynamics 10µF
1kΩ University of Texas
J1 R24
D2 + + + C39
D6 5 10µF
R18 R23 R25 C42 C37
0Ω 470µF 10µF
1
3 8
6 Setpoint Signal 2-3, 6-7
LM79L12M
1
-12V
INA128 U13
2 Vs -15V
5
R19
+12V (open)
U9 C1 +15V 8 1
PID LM78L05M +5V
Single or Multiple U14
R21 R20 OpAmp, see notes
R26 (open) C2 2-3, 6-7 +
R58 (open) 0Ω R2 R1 C40
10µF
R3
2
8 - 6
R27 OPA
+
C9 3
C34 D3 4 1 0.1µF + U2 R10
R4 1kΩ
10µF C4 R13
R28 2 Trimpot C3
1kΩ R15
3 1kΩ
3 R5 Output Rectifier
5
+ 2
8 R29 INA105 - 6 R14
J2 2 6 2 R61
R31 0Ω R6 OPA 1kΩ
C35
D4 4
Monitor
Output
1 3 - 6 2
10µF + U3 R11 OPA D1
U1
3 - 6
C6 1kΩ + OPA
3
1 U5
R59 + R17
R30 R32 (open) 2 R35 U6 1kΩ
(open)
R33 (open) R7 R8 R16
Potentiometer Output Inverter
(front Panel) 1kΩ
3 C5
R9 R12
-12V 2 1kΩ
R40 - 6
R34 0Ω OPA R50
+12 3
R41 + U4 R52 1kΩ
6 3
BUF634
R60
U10 R51
Photodiode U7
AD8304 Vlog R54 R53
1 14 R43 6 3
R38 BUF634
2 13 Control
C7 Signal
R56 10nF 3 12
R39 U11 Out
4 11
J3 J5
5 10 R42 R44 J4
6 9
R36 Current/
7 8 R37 Voltage R55
1 R45 R47
8 + 3 Sense Input SR20
6 4-point
C0 INA128 sense resistor J5
1nF +5V - 2
5
C8
0.1µF U8
R46 J6
J7
