Relay (NO) that closes when a certain power is drawn from a load

I would like to know if there are any devices that can perform a specific task. I need a device that measures power consumption. In the case that power consumed is larger than some threshold, I would like a relay (NO) to change to closed. I would also be looking for something that can support up to 200 volts and can measure amperages near 10 Amps. Does such a device exist? If so where can I find it?

by Jjohnston17
January 03, 2023

Many assumptions from my part, maybe inappropriate in your case but here, a solution (an analog one, by opposition to use an MCU).

The circuit turns on the lamp when the load is at one watt. Run the simulation, time domain simulation, to see the moment when the lamp turns on, as I have set the voltage of the source V1 to increase.

It assumes that the load is resistive and constant.

by vanderghast
January 08, 2023

You can easily get a window of voltages (a LED turning on when the voltage is between two limits) with the TL431. Get the datasheet on ti.com site, check its figure 10-12. ti.com, T431

by vanderghast
January 09, 2023

Thank you for your suggestions. The source of my power will be solar panels. These output relatively consistent voltages (plus or minus 5 volts) during operational hours. I would like to have something that recognizes when the power drawn by a lot is above a threshold. When that power is exceeded I would like a relay to change from open to closed. Because the voltage is relatively constant, maybe I could use a device that determines if the current exceeds a certain value instead.

by Jrjohnston
January 09, 2023

Not a perfect solution, and I am looking for a better one (energetically). And maybe not really applicable either in your case. But if so, feel free to comment.

by vanderghast
January 10, 2023
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