Drive circuit for photoelectric sensor

Claim 2

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.

Claim 3

A drive circuit according to claim 1, said circuit further comprising: a drive current adjustment connected to said current source, said drive current adjustment allowing adjustment of the magnitude of said drive current to said light source for thereby setting a desired light source output based on a desired sensing distance for said sensor.

Claim 4

A drive circuit according to claim 2, wherein said drive current adjustment comprises a potentiometer.

Claim 5

A drive circuit according to claim 1, wherein said peak detector comprises a series connection of a diode and a capacitor connected to said lead of said light source, and wherein said feedback voltage is at a node between said diode and said capacitor.

Claim 6

A drive circuit according to claim 1, wherein said oscillator comprises a 555 IC timer, and wherein said feedback voltage is provided across a series connection of at least one resistive element and a capacitor, a trigger lead of said timer and a threshold lead of said timer being connected between said at least one resistive element and said capacitor.

Claim 7

A drive circuit according to claim 1, wherein said oscillator comprises a 555 IC timer, and wherein said feedback voltage is provided across a series connection of a first resistive element, a second resistive element, and a capacitor, a trigger lead of said timer and a threshold lead of said timer being connected between said second resistive element and said capacitor.

Claim 8

A drive circuit according to claim 6, wherein a discharge lead of said timer is connected between said first and second resistive elements.

Claim 9

A drive circuit according to claim 1, wherein said current source comprises first, second, and third solid state devices, each of said solid state devices having conducting and non-conducting states, first and second terminals for conducting current in said conducting states, and a third terminal for controlling said conductive states; and wherein said output signal of said oscillator is connected in series with said third terminal of said first solid state device, said second terminal of said first solid state device being connected in series with a combination of a diode and at least said third terminal of said second solid state device; and wherein a potentiometer for providing an adjustable potentiometer resistance value is connected in series with a parallel connection of said first terminal of said second solid state device and said second terminal of said third solid state device, said third terminal of said third solid state device being connected to said second terminal of said second solid state device, said first terminal of said third solid state device being connected in series with said light source; and wherein said drive current through said light source is proportional to said output signal of said oscillator and said potentiometer resistance value.

Claim 10

A drive circuit according to claim 8, said circuit further comprising a capacitor connected to said lead of said light source, said capacitor discharging through said light source when said third solid state device is in said conducting state.

Claim 11

A drive circuit according to claim 8, wherein said first, second, and third solid state devices are bipolar junction transistors.

Claim 12

A drive circuit according to claim 10, wherein said first solid state device is a pnp bipolar junction transistor and said second solid state device is an npn bipolar junction transistor , and said third solid state device is a pnp bipolar junction transistor.

Claim 13

A drive circuit according to claim 10, wherein said first terminal of each of said first, second, and third transistors is an emitter, said second terminal is a collector, and said third terminal is a base.

Claim 16

A method according to claim 13, wherein said drive current adjustment comprises a potentiometer.

Claim 17

A method according to claim 13, wherein said peak detector comprises a series connection of a diode and a capacitor connected to said lead of said light source, and wherein said feedback voltage is at a node between said diode and said capacitor.

Claim 18

A method according to claim 13, wherein said oscillator comprises a 555 IC timer, and wherein said feedback voltage is provided across a series connection of at least one resistive element and a capacitor, a trigger lead of said timer and a threshold lead of said timer being connected between said at least one resistive element and said capacitor.

Claim 19

A method according to claim 13, wherein said oscillator comprises a 555 IC timer, and wherein said feedback voltage is provided across a series connection of a first resistive element, a second resistive element, and a capacitor, a trigger lead of said timer and a threshold lead of said timer being connected between said second resistive element and said capacitor.

Claim 20

A method according to claim 17, wherein a discharge lead of said timer is connected between said first and second resistive elements.

Claim 21

A method according to claim 13, wherein said drive current adjustment comprises a potentiometer for providing an adjustable potentiometer resistance value, and wherein said current source comprises first, second, and third solid state devices, each of said solid state devices having conducting and non-conducting states, first and second terminals for conducting current in said conducting states, and a third terminal for controlling said conductive states; and wherein said output signal of said oscillator is connected in series with said third terminal of said first solid state device, said second terminal of said first solid state device being connected in series with a combination of a diode and at least said third terminal of said second solid state device; and wherein said drive current adjustment comprises a potentiometer for providing an adjustable potentiometer resistance value, said potentiometer being connected in series with a parallel connection of said first terminal of said second solid state device and said second terminal of said third solid state device, said third terminal of said third solid state device being connected to said second terminal of said second solid state device, said first terminal of said third solid state device being connected in series with said light source; and wherein said drive current through said light source is proportional to said output signal of said oscillator and said potentiometer resistance value.

Claim 22

A method according to claim 19, said drive circuit further comprising a capacitor connected to said lead of said light source, said capacitor discharging through said light source when said third solid state device is in said conducting state.