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Help me build a voltage monitor

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RJ8214

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Hi, I need help.

I have no idea how to build this one. I need a circuit that can read a voltage drop of 9V or below and flip on a relay, than turn the relay off when it reaches 24V to 30V.

The voltage input source is 24V which could be reduced if necessary.

Any help is appreciated.

Thanks
ROB
 

cesare

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Re: Voltage Monitor

You can use a reference and one or more comparator to drive th relais
 

plusminus

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Re: Voltage Monitor

more simple: use a 24V normaly close relais.
This will work if your switchlevels doesn't have to be very exact.
 

yeechyan

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Voltage Monitor

Using voltage reference, a few comparators and flip-flop will do.
 

laktronics

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Re: Voltage Monitor

Hi,
Use a comparator. Attenuate the input to 1/3 and connect to -ve input. To positive input connect a 5V reference and provide an additional hysterisys voltage of 3V. Now when the input is below 15V, the -ve input will be below 5V, and comparator output will remain high providing a 3V hysterisys voltage, thus making the total +ve input to 8V. Above 24V input, the comparator ouput switches to zero Volt, hysteris is removed and the +ve input goes to 5V. This state continues until the input falls below 15V. Connect a diode from out of the comparator to the hysterisys circuit to avoid interraction of reference with it.

Connect a relay driver to output of the comparator.
Regards,
Laktronics.
 

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