Interesting AC presence monitor

A few years ago I built my own boards to monitor AC availability in my home. I used one board per main circuit branch (I.e. a group of circuits protected by a common GFCI). I based my design on the MID400 AC Line Monitor Logic-Out Device. This chip, with the addition of 2 resistors detects the presence of AC and raises/lowers a 5vdc output to track the AC. I just fed the 5v signal into an I/O board and was done. These have served me well for the past 6 years. But, the boards were fairly large and I would have preferred something denser, and commercial.

Now I have another application for AC sensing (detecting the operation and direction of an electric gate motor). So, I started searching around again to see what was available. There are some new chips on the market. But, still pretty much what I already had. Then on YouTube I found this board. It has 8 AC inputs and 8 opto-isolated outputs. Perfect. The same board is also available in a 1 and 3 circuit (as shown in the video) configuration and can be found in Europe as well as Asia.

Note, this is not a current monitor or a voltage monitor. It simply detects the presence of AC. But, if you have a mission-critical system, like animal monitoring and feeding, etc., and you need feedback that something has actually operated, this may be exactly what you need.

WARNING: As the video makes very clear, you need to use this board very carefully as it has exposed AC line current on it. I will attach a backing board and then mount a small bit of plastic over the high-voltage area as well as enclose the board in an electric box.

Interesting. I've been using the Aeon Energy Monitor to do something similar, but this only works in some situations and the Aeon unit is not fool proof. It works for my situation because the pump I'm monitoring is on a dedicated circuit and it's easy to spot the change in current. I refuse to put the pump on an energy monitoring Z-Wave switch because it's too critical.

I keep hoping that someone will make a Z-Wave device that measures energy but doesn't act as a switch. Another possibility would be a WiFi-based approach that communicated back to a hub with an API (no cloud).

…I keep hoping that someone will make a Z-Wave device that measures energy but doesn't act as a switch. Another possibility would be a WiFi-based approach that communicated back to a hub with an API (no cloud).

You could combine this device with a Z-Wave contact sensor. But, you’d obviously want the Z-Wave device to be on another circuit.

You could combine this device with a Z-Wave contact sensor. But, you’d obviously want the Z-Wave device to be on another circuit.

Yes, that would work for my sump pump, but not for other things like the fridge (without running another dedicated circuit).

…Yes, that would work for my sump pump, but not for other things like the fridge (without running another dedicated circuit).

Or… I mounted my sensors at the breaker panel. That way you can use a multi-port I/O device, even a wired one if your server or ethernet is nearby.

Or… I mounted my sensors at the breaker panel. That way you can use a multi-port I/O device, even a wired one if your server or ethernet is nearby.

I hadn't considered that, and it is (of course) the smart play. I'd still need to isolate the appliances on their own circuits though, no?

I have a question
What do you actually want to measure?
Device is on.
Device gets ac, but is not running?

Under what circumstances does the device not get ac? Fuse blown? Or switch is off?

And if switch: where is the switch? Next to device or integrated or further away.

So what problem do you want to really solve?

If it’s ac available locally You could use a ble beacon hanging of the local ac through a ac/dc converter. The ble device will send a ping every second. If no ac no pings. You can receive the ble pings in various ways. ( ie pibeacon)

Karl.


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Karl - I'm not sure if your question was to me or berkinet...

I want to be able to sense if a critical piece of equipment stopped working. I don't care to measure energy usage per se, more like the lack of it.

…
I hadn't considered that, and it is (of course) the smart play. I'd still need to isolate the appliances on their own circuits though, no?

You can power the IO board(s) off the main breaker. Then, just assign a sensor to each circuit you wish to monitor. I have my IO board, the Indigo server, and the router on a UPS, so I also put a sensor on the main,

BTW, if you have GFCI breakers, they must each be in their own sensor board. Then cannot share a neutral.

I have a question
What do you actually want to measure?
… …If it’s ac available locally You could use a ble beacon hanging of the local ac through a ac/dc converter. The ble device will send a ping every second. If no ac no pings. You can receive the ble pings in various ways. ( ie pibeacon) …

You can, of course, just use a 5vdc poser supply to feed a digital input on an IO board. But, the beauty of the sensors I linked is their density (as long as you can share neutrals) and price. BTW, the separate neutral issue would apple to using a power supply as well after a GFCI.

You can power the IO board(s) off the main breaker. Then, just assign a sensor to each circuit you wish to monitor. I have my IO board, the Indigo server, and the router on a UPS, so I also put a sensor on the main,

We may be at cross purposes in that I think you're looking to monitor the presence of power on the circuit (has the breaker tripped?), where I'm looking to measure the lack of power demand over a specified period of time (has the fridge died?). In other words, to determine whether the power draw has exceeded X watts in Y time. Our fridge is powered by the same 20 amp circuit that powers everything else in the kitchen. So to monitor it reliably would require a dedicated circuit from the fridge back to the breaker panel.

Dave
You could split the power cord into the 3 wires - remove the outer insulation -
Then use one if the energy monitors (zwave wifi…) and put the current sensor around the hot wire.
That gives you the power and energy measurement you want just for the fridge

Or much simpler use a zwave switch with energy monitor. They resume the state they were in after power loss

Or am I missing something?


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Or am I missing something?

The switch bit. I'm not comfortable putting certain things on Z-Wave modules where the module contains a relay. I understand that they are supposed to revert to last state, and some of them have parms where you can "lock" the relay in the on position. Not good enough for me. I use an inductive sensor on our sump pump for this reason. If a Z-Wave switch were to get stuck in an off position, I'd be the proud owner of an indoor swimming pool. Splitting the wires and using an inductive sensor feels like too much of a hack to me. I'd rather run a separate circuit and use inductive at the breaker panel. The thing I'm stuck on is that it feels like such a simple thing. Imagine something like an Aeon Smart Switch 6 that doesn't have a relay in it.

berkinet, apologies if I've staged a coup on your thread.

There is an old Insteon device that does just that: just measure power
but if that’s your only Insteon device likely not a good idea.


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We may be at cross purposes in that I think you're looking to monitor the presence of power on the circuit (has the breaker tripped?), where I'm looking to measure the lack of power demand over a specified period of time (has the fridge died?). In other words, to determine whether the power draw has exceeded X watts in Y time.

Indeed. However. I would think the two ends are compatible, but different. So, I would then suggest that your real need is to measure the internal temperature of the fridge. Because, everything else is really just analogous (to a greater or lesser sense) to the temperature. In your case, I would still monitor the circuit to see that current was available and then place a temperature sensor (RTD, thermocouple, or thermistor), in the fridge. You could also measure AC at the fan or current draw on the hot wire to the fan. But, as noted, those two indicators will not guarantee the fridge is actually cold.