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Has utility power been restored?

MultiSync

Sep 19, 2015
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Need some advice on a photo switch application.

I have a portable emergency generator that uses an outdoor manual transfer switch.

The problem is that when switched to the generator setup during a power outage I have no easy means of knowing if or when utility power is restored. The electric utility meter has two status LEDs behind a small clear plastic window that are always ON when power is available. I would like to design a waterproof circuit (9-12Vdc source would be nice) that would use a light sensor that would trigger a relay to sound a small (remote-wired) buzzer and light to let me know (day or night) that power has been restored.

The LEDs in the meter are red & yellow. I would like to use a photodiode that has a sensitivity rating of 600uM (orange wavelength).
 

duke37

Jan 9, 2011
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I saw somewhere that ordinary LEDs can be used to detect light, I think they were used in the reverse bias condition. Some experimentation would be required to see if the wavelengths matched.

A comparator and device driver would complete the setup. 9 to 12V would be ideal to turn on a FET which could replace a relay.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
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Is your KWH meter new generation (Digital) that transmits the data to the utility?

Chris
 

AnalogKid

Jun 10, 2015
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Many photodiodes and phototransistors come with molded on lenses to narrow their detection angle. One of these pointed a one of the LEDs should be reasonably immune to false alarms, particularly if you differentiate (edge detect) the output.

ak
 

Arouse1973

Adam
Dec 18, 2013
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I saw somewhere that ordinary LEDs can be used to detect light, I think they were used in the reverse bias condition. Some experimentation would be required to see if the wavelengths matched.

A comparator and device driver would complete the setup. 9 to 12V would be ideal to turn on a FET which could replace a relay.

Yep, Green LEDs can be used.
 

Arouse1973

Adam
Dec 18, 2013
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Need some advice on a photo switch application.

I have a portable emergency generator that uses an outdoor manual transfer switch.

The problem is that when switched to the generator setup during a power outage I have no easy means of knowing if or when utility power is restored. The electric utility meter has two status LEDs behind a small clear plastic window that are always ON when power is available. I would like to design a waterproof circuit (9-12Vdc source would be nice) that would use a light sensor that would trigger a relay to sound a small (remote-wired) buzzer and light to let me know (day or night) that power has been restored.

The LEDs in the meter are red & yellow. I would like to use a photodiode that has a sensitivity rating of 600uM (orange wavelength).

I assume you want the buzzer to sound when power is lost. Otherwise won't it be sounding all the time when you have utility power?
Adam
 

AnalogKid

Jun 10, 2015
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If there is an AC outlet or other direct access to the incoming AC power line before the transfer switch, a fairly simple circuit could sit on the line, arm itself when power goes out, and beep when it comes back - ***without*** a power source to run the circuit throughout the power outage. If fact, IF a small piezo beeper is enough of a sounder, AND IF you are comfortable with building a small non-isolated power supply, THEN the whole thing is pretty simple.

Another thought - If you have an AC-powered buzzer and an AC-coil SPDT relay, the whole circuit can be done without any active electronics.

ak
 

Bluejets

Oct 5, 2014
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Hack into a no contact volt pen......
 

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