I have a crude power sensing system I built with an Arduino Pro, a GPRS shield, and a relay that will send me a text message when my power goes out. The Arduino is powered from a UPS, which will keep it going after the power fails. To sense a failure, I have a relay held closed by a USB wall wart pl…

Need transistor/circuit help for building a power sensing circuit.

system April 4, 2014, 3:22am 2

You can consider using a solid state relay,

For example, the VN540 from ST
Max power supply voltage : 45V
Input control voltage: 0~5V
Output current (CONTINUOUS) : 2.8A
http://www.st.com/web/en/resource/technical/document/datasheet/CD00070971.pdf

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