US 5,962,845 A · Drive circuit for photoelectric sensor

Abstract

A drive circuit for a photoelectric sensor which automatically adjusts the sensor response time with adjustments in the drive current to the light source based on a desired sensing distance. The drive circuit includes an oscillator for establishing an output signal having an output frequency. An output of the oscillator is provided as an input to an adjustable current source. The current source is connected to the light source for providing the drive current to the light source at the output frequency. A peak detector is connected to a lead of the light source for detecting a feedback voltage proportional to the drive current through the light source. The feedback voltage is provided as an input to the oscillator, and the output frequency of the oscillator is variable depending on the feedback voltage so that variations in the drive current result in corresponding variations in the output frequency and, therefore, the frequency of the drive current. With the sensor of the present invention, a single sensor can provide a continuously variable response time based on the application.

Claims20

Dependent claims

A drive circuit for a photoelectric sensor which provides adjustment of sensor response time corresponding to adjustments in drive current to a sensor light source, said circuit comprising:

an oscillator for generating an output signal having an output frequency which establishes said sensor response time,
a current source connected to said light source for providing said drive current to said light source at said output frequency, said output signal of said oscillator being provided as an input to said current source;
and
a peak detector connected to a lead of said light source for detecting a feedback voltage proportional to said drive current through said light source;
wherein said feedback voltage is provided as an input to said oscillator, and wherein said output frequency is variable depending on said feedback voltage so that variations in said drive current result in corresponding variations in said output frequency and said sensor response time.

2 more elements

A method of adjusting the response time in a photoelectric sensor having an adjustable drive current to a light source of the sensor comprising:

providing a drive circuit for said light source, said drive circuit comprising:
an oscillator for generating an output signal having an output frequency which establishes said sensor response time,
a current source connected to said light source for providing said drive current to said light source at said output frequency, said output signal of said oscillator being provided as an input to said current source;
a drive current adjustment connected to said current source for adjusting the magnitude of said drive current for thereby setting a desired light source output based on a desired sensing distance for said sensor;
and
a peak detector connected to a lead of said light source for detecting a feedback voltage proportional to said drive current through said light source;
wherein said feedback voltage is provided as an input to said oscillator, and wherein said output frequency is variable depending on said feedback voltage so that variations in said drive current result in corresponding variations in said output frequency and said sensor response time;
and
operating said drive current adjustment to vary the magnitude of said drive current, said feedback voltage thereby causing variation in said output frequency and said sensor response time.

6 more elements

Dependencies are inferred from the claim text.

Drive circuit for photoelectric sensor

Life of this patent

Drive circuit for photoelectric sensor

Life of this patent

Abstract

Claims20