The Model SS is an infrared safety light curtain that is designed to the IEC 61496 standard.

When properly installed, it protects the machine operator by passing an invisible infrared light beam across an area to be guarded and examining whether or not the light beam(s) are blocked. If the light beam(s) are blocked, monitored solid state outputs will open, issuing a “STOP” command to the machines normally closed (N.C.) “STOP” circuit.

The System is composed of a transmitting unit (EMITTER), and a receiving unit (RECEIVER). The entire system is control reliable Category 4 (per IEC 61496). A single fault anywhere within the Model SS will not prevent at least one of the solid state outputs from opening up, (allowing a “STOP” command) when either a beam is broken or an internal fault occurs.

Theory of operation.
The Model SS protects an area by projecting a curtain of infrared light. The infrared emitters and receivers face each other across the field to be protected. Each emitter/receiver pair is spaced along the length of the pylons at regular intervals from .5", up to 8" depending on the application. The smaller spacing are for finger guarding, the larger spacing are for body protection. The emitter/receiver pairs are scanned sequentially (one at a time) by a very short pulse of infrared light starting from bottom (cable end), and working up to the top, until every beam pair has been scanned. Two 16 bit computers in the emitter pylon and two 16 bit computers in the receiver pylon control the operation, as well as cross check each pylon.

The System.
The Model SS employs infrared technology in a small sealed NEMA 4 aluminum housing with an infrared passing (daylight filtering) acrylic lens. This system provides harmless invisible protection and an unobstructed view of the guarded area. There are two parts to the Model SS: An Emitter pylon and a Receiver pylon. The Emitter pylon has no outputs, but does contain a digital CAN data network to allow it to be linked to the Receiver pylon (although not required for operation). The Receiver pylon contains the digital CAN data network and two monitored solid state 24vdc outputs. Both pylons are synchronized to each other either via the CAN data network or electronically.

System Safety.
The Model SS incorporates redundant, and diverse technology that provides a backup for every system that could cause an unsafe condition. In the Emitter pylon, 1 CPU drives the Infrared LED’s while the 2nd CPU monitors to assure proper signals and timing. Improper operation from either CPU will turn off the Infrared LED’s. In the Receiver pylon, 1 CPU drives the Infrared receivers while the 2nd CPU monitors to assure proper signals and timing. Both CPU’s are required to drive the solid state outputs as well as monitor the condition of the output. Either CPU can shut down both solid state outputs. Signals shared between CPU’s are isolated from each other to prevent a failure of 1 microprocessor causing a failure in the 2nd. Watchdog circuits on the solid state outputs automatically shut off the outputs should either CPU slow down or lock up. Solid state outputs are turned on separately to be checked and assure neither output has been shorted, before fully turning on.

Design Criteria.
Designed to meet IEC 61496-1 & 2, UL 1998, UL subject 491, OSHA, ANSI, CSA, ANSI-RIA R15.06-1999

Microprocessor redundancy for both Emitter and Receiver pylons

Redundant, monitored, 24vdc solid state outputs (PNP)

Watchdogs on CPU’s and outputs prevent unintentional output during lockups.

Specifications and Dimensions