Browse Prior Art Database

Online Optical Sensor Malfunction Detection

IP.com Disclosure Number: IPCOM000046924D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Glembocki, JS: AUTHOR [+2]

Abstract

Described here is circuitry for detecting a faulty optical sensor to prevent damage to product and machinery in a manufacturing line by programming corrective action or stopping the machine before damage occurs. The drawing shows a system block diagram. The controller will perform an on-state diagnosis and an off-state diagnosis of the sensor. The sensor will be diagnosed defective if it fails either portion. On-State Diagnosis The sensor is considered to be on when a target is present and reflects light from the sensor's light source to the light detector. With these conditions active, the detector transistor is saturated and its output is logically low. The controller can read this state through the digital input tied to the light detector. The diagnosis sequence is as follows: 1.

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Online Optical Sensor Malfunction Detection

Described here is circuitry for detecting a faulty optical sensor to prevent damage to product and machinery in a manufacturing line by programming corrective action or stopping the machine before damage occurs. The drawing shows a system block diagram. The controller will perform an on-state diagnosis and an off-state diagnosis of the sensor. The sensor will be diagnosed defective if it fails either portion. On-State Diagnosis The sensor is considered to be on when a target is present and reflects light from the sensor's light source to the light detector. With these conditions active, the detector transistor is saturated and its output is logically low. The controller can read this state through the digital input tied to the light detector. The diagnosis sequence is as follows: 1. The controller detects a low condition on digital input #2. 2. The controller sends a high level to the digital

output point, thus turning the light source off. 3. The controller reads digital input #2, which should now be high; if this point is low, the sensor is

defective. 4. The controller sends a low level to the digital

output point to turn the light source back on. Off-State Diagnosis The sensor is considered to be off without a target present to reflect light. When this is true, the output of the detector transistor is high with a small collector leakage current flowing through the transistor. Turning the light source off under these conditions will reduce this current from 0.7 mA to 100 nA. The digital comparator is biased such that its output is high when Ic =
0.7 mA and low wh...