Power remote systems show inductive reasoning.

The power of today's industrial controls--driven by demand for defect-free, unmanned production--allows design engineers to put more sensors and actuators on machines to bring high-level feedback and functionality to the part or tool interface.

The thing is, there's always been one low-tech catch: To transmit power and signals, it took a mechanical contact device--a slip ring, power track, or simple plug--to effect the connection. And mechanical contacts are all susceptible to dirt, wear, contamination, corrosion, and damage.

Now, all that has changed. Noncontact power remote systems eliminate "hard" connections to sensors or actuators on tooling, dies, pallets, and fixtures. Power remotes eliminate connect and disconnect time, as well as repair costs and downtime due to damaged cords and connectors. Systems can transmit power and sensor signals across an "air gap" up to 15mm and provide one amp of auxiliary power without a physical devices to the control or power source.

Working principles

In practice, a "local" power remote head with internal coil is mounted and wired to a control or programmable logic controller (PLC). The local-head coil converts DC supply voltage into an oscillating signal so that it can travel inductively (via flux lines) across a predetermined air gap and centerline offset to a "remote" head with its own internal coil. The remote head is mounted on the moveable or removable component such as dial tables, fixtures, toolings, and molds. When the remote head and local head align, the oscillating signal changes back to DC voltage in the remote head, producing drive current to power sensors or other devices.

Sensor signals (voltage outputs) return from the remote head to the local head in the same way. Circuitry inside the local head converts the inductive energy back to the DC voltage, which can be processed by any control or PLC. Any standard two- or three-wire DC sensor or mechanical switch can be used as a detector including inductive, photoelectric, magnetic, capacitive, ultrasonic, fiber optic, and mechanical switches.

Because the local and remote heads respond only to each other, no false outputs result from metal chips or other debris found in manufacturing environments. Heads are CE-rated and sealed to IP67 for reliable power and signal transmission in environments with dust, oil, coolant, metal chips, and other contaminants.

Since power remotes operate at relatively high frequencies, filtering requirements are low and a large capacitor is not required on the remote side. Also, because frequency is proportional to flux density, only a small magnetic core is needed for higher frequencies, making the heads compact and highly efficient, electrically and electronically.

Power factors

Key to the successful operation of the detecting sensor is the remote head's drive current. The amount of drive current is a function of head size, distance between the heads (air gap), and the amount of centerline offset. Peak performance requires prime axial alignment and air gap distance, as shown on pg 29.

Close axial alignment allows increased variation in air gap while a minimal air gap allows for slight misalignments of head centerlines. As the illustration shows, heads must be no more than 7mm apart to deliver one amp of drive current. With an air gap less than 3mm the lines of flux between heads cannot interact properly, neutralizing the electrical induction and preventing power and sensor signals from being transmitted.

Neither plastic nor glass hampers power or signal transmission. Plexiglas actually helps signal transmission because it is slightly more permeable than air. Heads can also spin as long as they maintain axial alignment and proper air gap.

Power remote systems place no special demands on the control. An ordinary in-zone signal must be addressed in the control's application programming. The in-zone signal acts as a system check, telling the control that the heads are properly aligned (within set parameters) and signals are being passed between heads.

Systems are available in the Standard 12 VDC and High 24 VDC versions.

The inherent shock- and vibration-resistance of power remote technology has also produced two application-specific systems: the T-Slot Power Remote and the Thermal Power Remote. Developed specifically for the stamping and forming industry, the T-Slot Power Remote system has its remote head "buried" in a standard 1" T-slot. The Thermal Power Remote system provides non-contact thermocouple data transmission for plastics molds, forging dies, and heat treating furnaces.

Standard Power

The Standard Power Remote system transmits 12 VDC and 5 to 100mA of drive current to power up to eight sensors. Standard Power Remotes are available in single-, four-, and eight-sensor systems. Heads for single- and four-sensor systems use M18 or M30 tubular nickel-plated brass housings, sending 530 mA drive current across an air gap up to 8mm. Eight-sensor systems use 80x40 mm "puck style" Polyamide heads, sending 20-30 mA of drive current across an air gap up to 15 mm.

Standard systems require amplifiers--one per head--to manage sensor signals. Amplifiers are available in both PNP and NPN versions.

High Power

Able to transmit 24 VDC at 1 amp to a remote location, the High Power Remote system allows bidirectional transmission of up to eight signals for sensors. At the same time it provides up to eight outputs to trigger actuators, relays, and solenoids. An auxiliary, remote power supply provides a 24 VDC output to drive components such as servomotors that demand more power than actuators or relays.