Multipurpose Analog PID Controller

Transcription

1 Multipurpose Analog PID Controller Todd P. Meyrath Atom Optics Laboratory Center for Nonlinear Dynamics University of Texas at Austin c 00 March 4, 00 revised December 0, 00 See disclaimer 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 / Amp directly, temperature controller, 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 control 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 / Amp of current either as a control single or directly driven current controller. The circuit requires a dual ± V supply. As mentioned, the circuit my be set to use single or multiple opamp PID, use the single or the multiple opamp PID hookup as in the table: Please send comments, questions, corrections, insults to [email protected] 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.

2 Single OpAmp PID hookup Use C to C, R to R4, U, U Omit C4 to C, R to R9, R, R, U to U Short a R0, R Proportional Gain (R R)/R Integration time R C Differentiation time (R R) C Notes: R4 limits differential gain, C gives high frequency rolloff. Multiple OpAmp PID hookup Use R to R, R to R9, (R0 to R = kω) C, C4 to C, U to U Omit C, C, R4 Short a C Proportional Gain (R R)/R Integration time (R R) C4 Differentiation time (R7 R) C Notes: R9 limits differential gain, C gives high frequency rolloff. a use a 0 Ω resistor, 0 package. The summer used for the multiple opamp PID is an inverting summer, in some cases, it is desired to reinvert the signal. Use as in the table: Output inverter option used Use R4, R = kω, U Output inverter option not used Omit U Short a R4, R a use a 0 Ω resistor, 0 package. The circuit is naturally bipolar, however, some cases require a unpolar output. Use the simple diode rectifier as in the table: Output rectifier option used For positive output only, use R7 = 0 kω, D For negative output only, use R7 = 0 kω, D (reverse diode direction drawn on schematic and layout) omit R in either case. Output rectifier option not used Omit R7 Short a R a use a 0 Ω resistor, 0 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:

3 Supply decoupling caps associated with ICs IC Capacitors Value U C0,C 0. µf U C,C 0. µf U C4,C 0. µf U4 C,C7 0. µf U C,C9 0. µf U C0,C 0. µf U7 C 0. µf U C,C 0. µf U9 C4,C 0. µf U0/U C,C7 0. µf U0/U C,C9 0 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: J, D, R Short: R, R7 Omit: R9 to R, R to R, R, R9 D, D4, C9, C4, C, U9 Potentiometer input Use: R or R (trimpot or potentiometer), (zero adjust) only R, R7, R9, R0, C9, C4, C, D, D4 Short: R, R7, (R and R4) or a (R and R) Omit: J, D, R to R0, R to R, U9 Analog input with zero adjust Use: J, D, R, R or R (trimpot or potentiometer), R, R7, R9, R0, C9, C4, C, D, D4, U9 Short: (R and R0) or b (R9 and R) and (R and R4) or a (R and R) add in gain adjust when using U9, use R to R, 0 kω the gain is b RR4R Invert setpoint signal Short: (R and R0) or (R9 and R) omit other, remember that pin of U9 is noninverting and pin is inverting. Unipolar zero adjust (short R, omit R, D, C4) or (short R9, omit R0, D4, C) use R7 or R9 as 0 Ω as appropriate. a Potentiometer direction Short: (R and R4) or (R and R) omit other, the direction of increase depends on if it is hooked to the inverting or noninverting 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

4 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. R4 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 SR0 Watt 4point sense resistor (Caddock Electronics). Depending on the resistance used, this resistor can directly measure up to 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 / 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: R to R9, (R or R0), C0, C7, C, U7 Short: R40 Omit: J, R4, R4 to R47, R4, U Current/voltage sense Use: J, R4 to R4, U Short: R4 Omit: R40, R to R9, R47, R, R0, C0, C7, C, U7 High current sense Use: R4 to R44, R47, U Short: R4 Omit: J, R40, R to R9, R4, R4, R, R0, C0, C7, C, U7 connect up to A (depending on R47 value) through J to J Direct output current sense Same as high current sense, but short R4, omit R, for use with the buffer output stage. connect load across J to J7. For the BNC connectors, the board is setup to accept either the right angle receptacle (7) or the vertical receptacle (7). 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

5 Figure : A board set up for a laser intensity control circuit.

6 Analog Control Input J C4 0µF C 0µF R R0 V D V D D4 4 R9 (open) R0 4 R R R9 Photodiode R C0 nf R C7 0nF R 0Ω R9 (open) R (open) R7 Trimpot R 0Ω R (open) R (open) R (open) R4 0Ω U7 AD C 0.µF R R4 R INA R0 0Ω Potentiometer (front Panel) R7 R7 U9 Vlog V J Monitor Output R C9 0.µF R40 R R9 Setpoint Signal Vs R4 INA0 U R4 Multipurpose Analog PID Controller Todd Meyrath Atom Optics Laboratory Center for Nonlinear Dynamics University of Texas INA U R4 R44 R4 R R9 R C C R4 R4 R C R R7 Version.0 March, 00 J C Current/ Voltage Sense Input R R U C4 U4 U C R0 R R R47 SR0 4point sense resistor R4 J J PID Single or Multiple OpAmp, see notes External Power Connections R V U V C4 470µF C4 470µF V R4 C 0µF C7 0µF R R U Output Inverter R R Power Supply Connections D D LM7LM U LM79LM, 7 U, 7 LM7L0M U4 U0, 7 R BUF4 BUF4 U Output Rectifier D C 0µF C9 0µF R R7 C40 0µF V V V R0 R Control Signal Out J4 J J7