Bar code scanner with DC brushless motor
First Claim
1. In a laser scanner including a rotating scanning element, a motor and associated circuitry, the improvement comprising:
- said motor being a DC brushless motor,said DC brushless motor connected to the rotating scanning element, the motor being closed-loop velocity controlled and including a hall effect device,motor detector circuitry means for receiving a hall effect signal from the hall effect device, and including means for deriving a voltage proportional to frequency of the hall effect signal, means for comparing the derived voltage to a reference voltage representative of a minimum permissible operating speed, means for outputting a voltage signal which indicates either up to speed, i.e. within permissible speed range, or not up to speed, and means for shutting off a laser of the scanner when the motor is not up to speed.
6 Assignments
0 Petitions
Accused Products
Abstract
A laser scanner having a rotating mirror, such as a POS scanner as used in supermarkets, uses a closed-loop velocity controlled DC brushless motor for rotating the mirror. In addition to providing a hall effect motor speed signal which is used for monitoring and safety features in association with the scanner, the DC brushless motor provides the advantages of greatly reduced power consumption, decreased temperature rise, less electrical noise in the analog scanner circuitry, reduced cost, and greatly reduced size, sometimes over 80%. The use of the inherent motor speed signal from the DC brushless motor also enables elimination of costly mechanical windswitches as typically used in prior scanners.
100 Citations
9 Claims
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1. In a laser scanner including a rotating scanning element, a motor and associated circuitry, the improvement comprising:
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said motor being a DC brushless motor, said DC brushless motor connected to the rotating scanning element, the motor being closed-loop velocity controlled and including a hall effect device, motor detector circuitry means for receiving a hall effect signal from the hall effect device, and including means for deriving a voltage proportional to frequency of the hall effect signal, means for comparing the derived voltage to a reference voltage representative of a minimum permissible operating speed, means for outputting a voltage signal which indicates either up to speed, i.e. within permissible speed range, or not up to speed, and means for shutting off a laser of the scanner when the motor is not up to speed. - View Dependent Claims (2, 3, 4)
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5. A method for producing a signal indicating motor speed for use in shutting off a laser for safety purposes in a laser scanner having a motor-driven rotating scanner element, comprising the steps of:
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providing a DC brushless motor connected to drive the rotating scanner element, the motor being closed-loop velocity controlled and including at least one hall effect device, receiving a signal from the hall effect device, deriving from the signal a voltage proportional to frequency of the signal, comparing the derived voltage to a reference voltage representative of a minimum permissible operating speed, outputting a voltage signal which indicates either up to speed, i.e., within permissible speed rang,e or not up to speed, and shutting off the laser of the scanner when the motor is not up to speed. - View Dependent Claims (6, 7, 8, 9)
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Specification