A group of PDP-14 systems can be moni-

. The PDP~ 14 is a solid-state program- mable controller for repetitive manufac- turing operations. It accepts inputs from two-state devices such as limit switches, push buttons or pressure switches and, in accordance with input conditions and a predetermined control sequence, turns on or off outputs such as solenoids and motor starters. The control sequence for a par- ticular application is stored in the memory section of the PDP-14.

he PDP-14 can control any operation or process that can be broken into a number of discrete steps or logical expressions, each with just two states; i.e., status inputs are either on or off, and the control opera- tion selects outputs and turns them on or off. This type of control sequence is used in most mass production equipment and materials handling systems. It is also used in such diverse industries as automobiles, textiles, food processing, chemicals and utilities.

To direct specific control operations, the PDP-14 system uses an easily alterable memory. Convenient programming tech- niques allow each user to design a memory to suit his unique control needs. The en- tire control process can be redefined by changing the memory.

The PDP-14 system is designed to operate independently or with computer moni- toring or control. Since the PDP-14 can access all control inputs and outputs, the added monitoring components are simply a general-purpose computer and a simple interface device (available from DIGITAL).

A group of PDP-14 systems can be moni-

tored by a single computer using a serial

line interface to provide status and mal-

function reports for a large control

complex.

The PDP-14 control system is designed to directly replace conventional systems with a minimum of special considerations. The equipment uses standard 115 V AC (or standard DC levels) input and output signals. To allow for easy repair or re- placement of parts, the functional units are divided into plug-in modules contain- ing solid state devices and other com- ponents.

1

l

~

^{A I ~}

^'"'

^{At lf.j 1}

The PDP-14 is a direct replacement for this typical control system.

As in ordinary control systems, the PD P-14 accepts low power AC signals at its inputs, determines which signals are necessary for a given machine function, and then turns on and off the required outputs.

The PDP-14 system is a unified assembly of four basic units: input boxes; output boxes; control unit; and accessory boxes (timers, retentive memories, etc.).

I~ I

1,• '1 <:I, ' p

LB

The input (I) boxes and output (0) boxes provide an interface or buffer between the 115 VAC control signals (or DC level) from the controlled device and the PDP-14 control unit.

In the PDP-14 control system, the low-

vol tage solid-state circuits of the unit

test and direct the 115 V AC circuits of the

controlled device through control cables .

The I and 0-boxes provide complete iso-

lation of the PDP-14 internal circuits from

the AC power supply. Each I or 0-box

handles a small number of AC circuits and

has its own control cable to the control

unit.

The circuits of the control unit and its memory perform the 3 basic operations of any control system:

1. TEST inputs or outputs for state (ON or OFF)

2. DECIDE what control function is required

3. SET outputs ON or OFF (execute the control decision)

MEMORY

The memory in the PDP-14 system is either a "Read Only Memory" (ROM) or a "Read/Write Memory."

The Read Only Memory cannot be altered electrically (that is, written on). It contains a pattern or "braid" of wires woven to- gether. This pattern is actually a list of per anently wired electrical instructions which are read by the control unit to de- termine system operation.

The control is a sequential operation simi- lar to scanning a relay ladder diagram rung by rung. Each rung of the ladder

represents a specific group of sensed input conditions which must be satisfied to cause a change in the condition of the out- put. The ROM contains instructions in small groups, each corresponding to a sin- gle rung in the ladder. It directs the con- trol to select each input specified in a group and test whether it is on or off.

Based on the test results, the specified out- put is s ected and set on or off. The con- trol then continues to the next group of inputs and outputs and repeats the proc- ess. This action occurs one instruction at a time but at a speed in thousandths of a second.

Many applications for the PDP-14 require maximum flexibility during the transient start-up periods or where environmental noise and temperature are not severe.

These conditions gave rise to the Read/

Write Memory MM14-A.

The Read/Write Memory for the PDP-14 is one 4,000 word memory, industrially packaged in its own mounting box. The MM14-A can only be used with the PDP-14, not the PDP-14L. It can be easily altered, which allows the user to change the control sequence whenever he chooses.

The user can load or change the contents

of the memory with the same equipment

he used to develop his control. What this

means is that the memory can now be

loaded as soon as the control program is

completed. In addition, the memory con-

tents can be altered as soon as the new

control program has been developed. This

significantly reduces the amount of time

required to change the contents of the

memory.

A control system may require a group of preset status signals which cannot be gen- erated by direct machine operation. For example, timers can provide duration and sequencing control for a controlled device.

These functions are performed in the PDP-14 system by accessory boxes.

The A-box shell is mechanically identical to the I or 0-box and is mounted in the same way. It is enclosed by a metal cover.

An A-box has 8 slots, each of which ac- cepts any one card to provide the follow- ing functions: timers, retentive memories or storage cards. Each implements two identical functions for a total of 16 func- tions per A-box. The K302 timer provides timing in the range of 0.01 to 30 seconds as supplied. With a simple modification the range can be extended to 4 minutes, 45 seconds. The K274 retentive memory permits storing crit~al inform~tio..D.~hidi must be retained even i? the control unit Ioses power. I he Ro2"2 s'tor~card p~

vides temporary storage, which is cleared whenever power is lost.

The PDP-14 system design enables the user to add optional computer monitoring at any time. A small, general-purpose computer can be connected through con- trol cables to the control unit, and certain monitoring modules also installed. The computer can then either monitor any control operation of the PDP-14 system or it can monitor the status of any input or output and convert this information into a printed record if desired. The computer can also assume command of any control function, either on a standard or emer- gency basis. Some of the most suitable computers for mQJlitor.i.og,.tbe PDl?...14 ate ille DIGIT AL PDP-8 or PDP-11 family

computers. I hey are inexpensive and convenient to use and install. The moni- toring modules to adapt these computers to the PDP-14 are available.

Computer interfaced operations of the PDP-14 are more fully described in "The PDP-14 in Computer Control."

The PDP-14 is designed for control engi- neers, not computer programmers. There are two al terna ti ve memory development aids: (1) CRT-14 or (2) SET-14, BOOL-14 and SIM-14. To program control systems using relay S'ymbology, the control engineer can use CRT-14. If the control engineer prefers to program using Boolean equa- tions, BOOL-14 and SIM-14 are available.

They are program tapes written.for the cimtrol engineer andate..pI.Q.YM;ie~ d - ~ith

every .. PO.f-14 ~ste.m.~ These OQerate o. ;Un...__

mP-8 famil.Y. . com.nYt~ .... qnd Teletype.and

enable thecontrol engineer to convert his

sequence of operations into the PDP-14

memory without using computer pro-

gramming techniques.

Control Relay Translator-14 enables the control engineer to develop his PDP-14 program directly from a relay ladder dia- gram and debug this program on-line with a PDP-14 controller and his equipment.

After the PDP-14 program has been fully debugged, GRT-14 can output a binary tape from which a read only memory can be woven or the CRT-14 program can be directly entered into the PDP-14 read/

write memory. CRT-14's binary output tape can also be input to SIM-14 for editing and both off-line and on-line simulation.

The CRT-14 program runs on an 8K PD.P-8 computerwith an ASR33 Teletype. An LA30 Teleprinter or VTOS Alphanumeric Display can also be used as console or printer devices.

The control engineer, who must be famil- iar with ladder diagram schematics,

develops his PDP-14 program by entering one ladder diagram at a time via the con- sole keyboard. He keys in each normally open or closed input contact, normally open or closed output contact, branch point, and driven output coil.

Once the drawing of the input circuit is the

same as his schematic drawing, he may

then store this circuit in the PDP-14 pro-

gram storage. A series of these circuit

diagrams, entered and stored in this way,

constitute a PDP-14 program. All stored

circuits may be recalled, deleted, listed,

and edited at any time. As the control

engineer is storing these circuits and

building his PDP-14 program, he may run

this program on-line, actually running

his equipment and interrogating inputs

and outputs and setting outputs on or off.

In order to develop a PDP-14 program using CRT-14, the control engineer must first prepare his ladder diagram, make wire terminal assignments and number branch points. He may then enter and store the diagrams one at a time.

LADDER DIAGRAM PREPARATION

WIRE TERMINAL ASSIGNMENTS

NUMBER BRANCH

POINTS

ENTER LADDER DIAGRAM

The following are the ladder diagram de- sign rules for CRT-14:

1. One output circuit may contain up to ten parallel lines. Each line may con- tain a combination of eleven input con- tacts, output contacts, and branch points.

2. The same contact may be used in as many circuits as necessary.

3. All branch paths must return to Ll (AC line or DC supply).

4. All inputs and outputs can be numbered using the X and Y symbology or straight number method with inputs from 0-377 octal and outputs from 400-776 octal.

When the circuit conforms to the CRT-14 design rules, and all wire terminals and branch points in that circuit have been as- signed, the control engineer is ready to enter his circuit into CRT-14 using the following keyboard symbols:

SYMBOL Ll

B -H-

---tf-- - { } -

OUfFUTS rEllMINAi.S

ICR •Ol

2CR 402

JCI (03

You Type:

LI

-H- I B2

LI

--H- 401 B2 -H-2 --H- 402 BJ LI

---;If- 403 ---H-3

Bl

-{ }-- 401

Line 1 (AC line or DC supply)

Branch Point

Normally open contact Normally closed contact Output driver (end of circuit)

·~~~

t---l~

OJ

Description of Item

(Reference AC line

or DC supply)

(N/ 0input#1)

(Branch point 2)

(Reference AC line

or DC supply)

(N / O contact #401)

(Branch point 2)

(N/ 0 input #2)

(N! O output #402)

(Branch point 1)

(Reference AC line

or DC supply)

( N/ C output #403)

(N/ O input #3)

(Branch point 1)

(Output driver 401-

end of circuit)

The PDP-14 is designed to be maintained by the user. Although computer-based diagnostics and DIGIT AL field service are available, they are generally not neces- sary for the maintenance of the equip- ment. The first step in..s~w~ ...

PDE-14 .anff._t~e s_qntr<?.lle~ eq}lipment is to distinguish equipment failures in the controlled device from those in the con- trol ~i~te_m.,_ With the PDP-14 Program- -mable Controller, a systematic mainte-

nance procedure is presented.

The PDP-14 is equipped with i~Js.el.2L ~.

famps on each itIJ?_;i~~.l!,U,mt. Used in coniunction with these lights is an inter- rogator box (BT14-A) which allows main- tenance personnel to differentiate between failures in the PDP-14 and failures to a specific 1/0 field device or a specific com- ponent on the PDP-14.

Let's use the inputs and outputs in the diagram to describe a maintenance pro- cedure. First, let's say that to activate Solenoid 25, both Limit Switch 10 and Limit Switch 16 must be on. However, Solenoid 25 was not activated. What do we do?

-

STEP 1. If the indicator lamp for Solenoid 25 on the 0-Box is off, look at the indi- cator lamps on the input box for LS10 and LS16·

A. If either LS10 or LS16 indicator lamps are off, the limit switch is not operating and should be re- placed.

B. If both LS1oand LS16 indicator lamps are on, use the interrogator box.

This step has told us that the malfunc- tion is not in the field device, but in the controller itself.

STEP 2. Use Interrogator Box to test the output to Solenoid 25.

A. If the test light on the BT14-A is on, the trouble is either a bad triac driver or a blown fuse on the output module (K614), possibly caused by a shorted solenoid. Replace the faulty component.

B. If the test light on BT14-A is off,

use the BT14-A to test inputs LS10 and LS16 .

STEP 3. Use Interrogator Box to test in- puts LS10 and LS16 .

A. If the testlight on the BT14-A for either LS10 or LS16 is off, replace the input converter module (K578 or K579).

B. If the test light on the BT14-A is on, for both inputs, replace the output enabling module (K207).

If timers or storage elements are part of

the sequence, treat them as outputs and

perform the same maintenance proce-

dures. For more detailed information,

consult the PDP-14 Maintenance Manual.

INPUTS Eight I-boxes of 32 inputs each, total of 256 inputs. All inputs 115 V AC, 1.5 VA, or 10-55 voe.

OUTPUTS 16 0-boxes with 16 outputs each, total of 255 outputs.

All outputs 115 V AC, 500 VA max., or total distributed load of 250 VA each.

DC: 10-250 VDC (one amp per output switched to ground).

CONTROL UNIT Accepts memory con- taining over 4,000 separate instructions.

Requires 115 VAC, less than 160 VA. The control program is scanned at approxi- mately 15 milliseconds per lK or PDP-14 memory.

Dimensions: PDP-14 Control Unit:

24

¹¹

w x 17-5/8" h x 8

¹¹

d Interface Boxes (I,0,A):

4-3/8" w x 10-7 /16

¹¹

h x 7-1/8

¹¹

d

Ambient

Temperature: 0° to 70° C.

Electrical: Meets J.I.C. Electrical Standards for mass pro- duction equipment (EMP-1-1967).

Line Voltage:

Line

Frequency:

Input Box:

Output Box:

105-125, 210-240 VAC single phase

47-500 Hz

AC: Reactive load, nominal 1.5 VA per input

DC: 10-55 voe (above with external resistor) AC: 4000 VA to its com- bined 120 V AC loads (individual output circuits can supplx_ ~.1212 500

DC: ^10-250 voe (1 amp per

output switched to ground).

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P 0 ^801< ~91. Crows Nest

N SW Au11rral1a 3065

Telephone (39-2566 Telex AA20740 C•ble D.g.tel. Sydney

MELBOURNE

60 Park Street South Melbourne. V1ctor10. 3205 Telephone 699-2888 Telex: AA-40616 PERTH

643 Muf/By Street

West Porth. Wellern Australrn 6005 Tolephone 21-4993 Telex AA92140 BRISBANE

139 Mcnvalo Street, South Brisbane Oueenslund. AuatraHo ~101 Telephone 44-4047 Telex AA-40616 ADELAIDE

6 Montrose Avenue Norwood. South Austral1e 5067 Telephone 63-1339 Tolex AA82825

NEW ZEALAND D1g1tal Equipment Corporalron lid AUCKLAND

Hilton HovH. 4'.Xl Queen Sueet. Box 2471 Auckl•nd. New Ze11tend

felcphOM 75533

JAPAN

01g1t1l Equipment Corporation ln1ernotlonal TOKYO

Kow11 Building No. 17. Second Floor 2-7 N11h1-A1ebu l·Chome Mm•to-Ku, Tokyo. Jepan Telephone 404·5894/6 Telex; TK-6428

BUENOS AIRES Coa:11n SA

Virrey del Pino 4071, Buenos A1res Telephone. ~2-3165 Telex 012-2264 BRAZIL

RIO DE JANEIRO - GB Ambnoi< SA.

Rua Ceara, 104. 2." e 3. • andere~

Fones 221-4560/44. 252-9873 Coble AAIOCARDIO SAO PAULO - SP Ambr1ex SA.

Rue Tupi, 535

Fono1 51-0912, 52-0655; 52-7806 Ceble AAl0CAA010 PORTO ALEGRE - RS Ambr1ex S.A.

Ruo Cel Vicente, 421, i.• ondar Fone1 24-7-411. 24-7696 CHILE SANTIAGO

Coeson Chile Ltda. (ulos only) Coa1lle 14588, Correo 15. Sen11ago Telephone 396713 Cable COACHIL INDIA

BOMBAY

Hlnd•tron Computers Pvt. Ltd 69/ A, L Jagmohond11s Marg Bomboy-6 (W.B.). lndlo

Tolephona 38·1815, 36-5344 Telex 011-2594 Plenty Coble: Tekhind

MEXICO MEXICO CITY Me.:11ek, SA.

Eugenia 400 Deplos 1 Apdo Poslol 12-1012 Mexico 12. D F.

Telephone (905) 536-03-10 PHILIPPINES MANILA

St•nford Computer Corpor.11t1on po. Boi< 1606

416 D111mennas St, Manila To!ephone (9-08-96 Tetexo 742-0352 VENEZUELA

CARACAS Cot11in, C.A.

Aportado 50939

Sabeno Cronde No I. Ceraca1 105 Telephone: 72·6662; 72-9637 Cable: INSTAUVEN

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