Photo controller for switching a load in a hazardous environment
First Claim
1. A photo controller circuit comprising:
- an output switching (OS) circuit comprising an alternistor for controllably completing and interrupting a power supply path between a power source and a load, and an optoisolator connected to the power source and to the alternistor for controllably gating the alternistor;
a light to voltage converter (LVC) circuit for detecting incident light and generating a direct current (DC) voltage proportional to the detected incident light;
a hysteresis control (HC) circuit comprising a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit, the state of the OS circuit being one of active to power on the load and inactive to power down the load; and
an intermediate switching (IS) circuit operable to controllably turn on and provide current to activate the optoisolator when the output of the HC circuit indicates the detected incident light is below a first selected level and the IS circuit was off, and to controllably turn off and reduce the current to deactivate the optoisolator when the output of the HC circuit indicates the detected incident light is above a second selected level and the IS circuit was on.
1 Assignment
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Accused Products
Abstract
A photo controller circuit for use in hazardous areas has an output switching (OS) circuit comprising an alternistor for ON/OFF switching of a load, and an optoisolator for gating the alternistor. A light to voltage converter (LVC) circuit generates a DC voltage proportional to detected incident light. A hysteresis control (HS) circuit comprises a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit. An integrator and switching (IS) circuit turns on and activates the optoisolator when the output of the HC circuit indicates the detected incident light is below a selected level, and turns off and deactivates the optoisolator when the output of the HC circuit indicates the detected incident light is above a selected level. The IS circuit time delays the output of the HC circuit prior activating or deactivating the optoisolator. The electronic components are rated for 125° C.
29 Citations
25 Claims
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1. A photo controller circuit comprising:
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an output switching (OS) circuit comprising an alternistor for controllably completing and interrupting a power supply path between a power source and a load, and an optoisolator connected to the power source and to the alternistor for controllably gating the alternistor; a light to voltage converter (LVC) circuit for detecting incident light and generating a direct current (DC) voltage proportional to the detected incident light; a hysteresis control (HC) circuit comprising a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit, the state of the OS circuit being one of active to power on the load and inactive to power down the load; and an intermediate switching (IS) circuit operable to controllably turn on and provide current to activate the optoisolator when the output of the HC circuit indicates the detected incident light is below a first selected level and the IS circuit was off, and to controllably turn off and reduce the current to deactivate the optoisolator when the output of the HC circuit indicates the detected incident light is above a second selected level and the IS circuit was on. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A photo controller circuit comprising:
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an output switching (OS) circuit comprising an alternistor for controllably completing and interrupting a power supply path between a power source and a load, and an optoisolator connected to the power source and to the alternistor for controllably gating the alternistor; a light to voltage converter (LVC) circuit for detecting incident light and generating a direct current (DC) voltage proportional to the detected incident light; a hysteresis control (HC) circuit comprising a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit, the state of the OS circuit being one of active to power on the load and inactive to power down the load; and an integrator and switching (IS) circuit operable to controllably turn on and provide current to activate the optoisolator when the output of the HC circuit indicates the detected incident light is below a first selected level and the IS circuit was off, and to controllably turn off and reduce the current to deactivate the optoisolator when the output of the HC circuit indicates the detected incident light is above a second selected level and the IS circuit was on, the IS circuit being configured to provide a selected time delay to the output of the HC circuit prior to generating the current to activate the optoisolator and prior to reducing the current to deactivate the optoisolator. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of photo-controlled switching of a load comprising the steps of:
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controllably operating a output switching circuit to selectively complete and interrupt a power supply path between a power source and a load; detecting incident light and generating a direct current (DC) voltage proportional to the detected incident light; generating an output signal depending on the DC voltage and the state of the OS circuit to indicate when the incident light is above and below selected thresholds, the state of the OS circuit being one of active to power on the load and inactive to power down the load; operating a time delay and activating circuit to controllably turn on and activate the output switching circuit when the output signal indicates the detected incident light is below a selected threshold and the time delay and activating circuit was off, and to controllably turn off and deactivate the output switching circuit when the output signal indicates the detected incident light is above a selected threshold and the time delay and activating circuit was on; and providing a selected time delay to the output signal via the time delay and activating circuit prior to activating the output switching circuit and prior to deactivating the output switching circuit. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification