Best way to monitor a power failure- F1616

[sequoia]

I am new to the F1616 and ladder logic but I have succeeded at logging counts of separate inputs, displaying it via the LCD or monitoring it over the web.

What I cannot figure out is how to detect the removal of power. I envision having a 12v or 24v signal to an input, and when this signal "goes away" I would like to execute a custom function that updates the LCD display with the word POWER plus sends me an email saying POWER FAIL. When the power is restored it would update the LCD display to remove the word POWER and send me an email saying POWER RESTORED.

The PLC and network gear all have battery backup-- so only the incoming signal to one of the inputs would be interrupted.

Can you suggest how I might approach this? I am seriously in the newbie baffled zone right now!

[support]

You can divide the 12V or 24V DC voltage into 0-10V range so that the F1616-BA can use its analog input to measure the voltage. Since F1616-BA analog inputs all have low impedance 20.0K ohm inputs, it is quite easy to do because all you need is to connect a resistor of suitable value in series to the 12V or 24VDC and it automatically divides down to the range.

For 12VDC, you can add a 10K Ohm resistor in series and the voltage measured by the ADC = 20/(10+20)*12 = 8V when incoming voltage = 12V and will be lower with lower input voltage.

For 24VDC, add a 39K resistor : 20/(39+20)*24 = 8.13V when input voltage is 24V.

You can decide what is the voltage that will trigger the shut down notification routine. You should then use a clock pulse to periodically execute a custom function to monitor your ADC input and once a power down is detected then trigger the custom function.