Help me build a voltage monitor

[RJ8214]

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]

Re: Voltage Monitor

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

 

[plusminus]

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]

Voltage Monitor

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

 

[laktronics]

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.