Allen-bradley Company, LLC

John E Callan

Anthony Gerard Gibart

Harold J Pollnow

Shigeru Ina

Kazuaki Kume

A programmable controller includes a number of equipment racks having slots which receive a processor module and a plurality of input/output modules. Each rack has a backplane which includes a number of buses for electrically interconnecting the modules therein, one of these buses carries slot address signals identifying the slot containing an input/output module which the processor module seeks to access. The backplanes of the racks are connected together in a daisy chain. Each backplane has a circuit which responds to the addresses of that rack's slots by producing enable signals for the module in the corresponding slot. This backplane circuit also subtracts the number of slots in its rack from the slot address and passes the result to the next rack in the daisy chain. By this justification of the slot address as it is passed down the daisy chain, each rack address decoder circuit can be hard wired to respond to slot addresses between zero and X, where X is the number of slots in that rack; regardless of the rack's relative position within the daisy chain and the range of virtual addresses for its slots.

Programmable controller module rack with a relative rack slot addressing

An a.c. input circuit for converting a sensed a.c. voltage into a logic level voltage includes a rectifier for converting the sensed a.c. voltage to a d.c. voltage which is supplied through a coupling impedance to the light emitter of an optical isolator. While the a.c. input voltage is below a first predetermined voltage, a switchable low impedance circuit path in parallel with the light emitter is rendered conductive to maintain a low impedance across the light emitter to prevent the light emitter from becoming conductive. A switchable high impedance circuit path in parallel with the switchable low impedance circuit path becomes conductive once the sensed a.c. input voltage reaches the predetermined voltage to drive the light emitter into hard conduction. The switchable high impedance circuit path remains conductive until the sensed a.c. input voltage drops below a second predetermined value, at which point the light emitter is turned off and the switchable low impedance path becomes conductive.

Optically coupled input circuit for digital control

A programmable controller has eight I/O buses which will support a corresponding number of I/O modules. The I/O capacity of the programmable controller may be increased by replacing four of the I/O modules with an I/O address module and three I/O interface modules that drive I/O expansion buses. Up to eight I/O racks, each containing three I/O modules and one adaptor circuit, can be connected to the I/O expansion buses.

Programmable controller with expandable I/O interface circuitry

A plurality of remote stations are sequentially addressed by a master controller to ascertain the status of associated sensing devices. The addresses are each comprised of a sequence of sinusoidal waveforms which are counted by the remote stations and compared with a preselected station number. Each addressed station responds by driving a communication line to a low voltage level for a time interval determined by the status of its associated sensing device.

Switch network

A latch-relay drive circuit includes a pair of switching devices for separately energizing the set and reset latch-relay coils. To prevent the latch-relay from remaining set once the power fails, an energy storage device, such as a capacitor charged from the power supply, is automatically switched across the reset coil by a switching circuit once the power supply voltage drops below a predetermined voltage thereby automatically resetting the relay.

Latch relay drive circuit

A summing watt-hour transducer is connected to a three-phase power line to monitor the energy being supplied to one load, and is connected to an ordinary watt-hour transducer that monitors energy supplied to a second load. A summing integrator circuit sums and integrates signals derived from the power line and the ordinary watt-hour transducer to obtain a voltage proportional to a unit of total energy demand. The summing operation is triggered by a signal from a control circuit that is responsive to contact closure pulses from the ordinary watt-hour transducer. Output signals from the summing integrator circuit are converted to contact closures for input of energy demand signals to an energy demand/schedule controller.

Summing watt-hour transducer

A circuit for sensing instantaneous current and voltage generates a digital output which indicates the power consumed over a time interval. The analog product of sensed current and voltage is converted to a pulse train in which each pulse represents a plus or minus increment of power. These pulses are either added to or subtracted from a total accumulated power number which is stored in a digital counter. The contents of the digital counter is coupled to a display to provide a readout of total consumed power.

Digital watts transducer

A solid state equivalent of a relay includes a pair of time delay circuits having inputs which couple to a pseudo coil terminal. One time delay circuit couples to drive a bilateral switch which simulates the operation of a set of normally closed relay contacts and the other time delay circuit is connected in series with an inverter gate and coupled to drive a second bilateral switch which simulates the operation of a set of normally open relay contacts.

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Milwaukee, WI, United States of America

John E Callan