# Looking for detector to detect if any current is being used by a device

Status
Not open for further replies.

#### higonnet

##### New Member
Let me explain in more detail!

I want to be able to know if an arbitrary device plugged into a standard AC outlet is drawing any current (i.e. is working.). I don't care to know how much current is flowing (I don't want a wattmeter), just if any current is flowing at all.

I further want this information (device working=current flowing/not working=current not flowing) to be transmitted to a computer (via USB?).

Somehow, I suspect that such detection devices must exist in the wide world out there, but I don't know what they might be called.

TIA
Bernard Higonnet

Last edited:

#### MikeMl

##### Well-Known Member
Clamp on Ammeter?

##### Banned
You still have to split the wires on the device to use a clamp on meter. The net current going through an AC cable when you measure both lines is 0. You could use a sensitive hall effect sensor, it should pick up some fluctuation, the magnetic fields oppose but they don't completely cancle each other out if you place the sensors very close to one of the conductors so you should pick up something.

#### tcmtech

##### Banned
MikeMI! Whos the man?

#### higonnet

##### New Member
I had hoped to be able keep secret that beyond knowing what is taught in high school or introductory college physics, my ignorance is great.

I was hoping that I could find off-the-shelf devices able to do what I want...

Failing that, a kind soul would have to produce a complete diagram, as I am unable to understand "Clamp on Ammeter"

BernardHigonnet

Last edited:

#### unclejed613

##### Well-Known Member
maybe try something like this? the more turns of wire on the secondary, the more sensitive it is. this provides a simple logic level output.

#### Attachments

• 54.7 KB Views: 101

#### colin55

##### Well-Known Member
You can convert an RCD (earth leakage detector) to detect the current. These are available as a separate item in Australia, in the $2.00 junk shops, for about$14.00
It trips at about 5 to 15mA.

This is the cheapest and best solution. It's already complete and ready to run. You just have to re-wire it externally).

Last edited:

#### MikeMl

##### Well-Known Member
You can convert an RCD (earth leakage detector) to detect the current...It trips at about 5 to 15mA...You just have to re-wire it externally).
Colin, they are called Ground Fault Interrupters (GFIs) over here. Seems when I looked inside one, both the Line and Neutral wires went through the center of a toroid. What would you do? Rewire it so only one of the load carrying wires goes through the toroid?

#### colin55

##### Well-Known Member
It's just the difference between the two conductors that trips the circuit. So if you just use one wire, and place it in the active line of your circuit, it will trip the RCD (provided it is powered), when a few milliamps flow.

#### KMoffett

##### Well-Known Member
Another option...Detects any current between about 0.1mA AC and the maximum diode current, to a load...and outputs an isolated logic level signal.

ken

#### Attachments

• 15.2 KB Views: 112
Last edited:

#### colin55

##### Well-Known Member
Why re-invent the wheel, when the device you need is already available for less cost than buying the components individually.

In the circuit above, the diode has to be a 15Amp device. You have to generate the 5v supply and provide a relay - it's totally unrealistic.

Last edited:

Colin55,

Ken

#### ccurtis

##### Well-Known Member
Colin, they are called Ground Fault Interrupters (GFIs) over here. Seems when I looked inside one, both the Line and Neutral wires went through the center of a toroid. What would you do? Rewire it so only one of the load carrying wires goes through the toroid?

That makes sense. The question I have is: can the output of the circuit that senses the torroid field then drives the latching relay in the GFI (which normally interrupts the HOT side when tripped) be used for the OP's purpose? I think it would probably require a little conditioning to be useful. I'd like to know what that signal is, myself.

As I see it, the biggest problem is getting the signals from all these outlets to the OP's computer. Maybe through carrier current transmitter?

#### KMoffett

##### Well-Known Member
In the circuit above, the diode has to be a 15Amp device. You have to generate the 5v supply and provide a relay - it's totally unrealistic.
15A/25V diodes are cheap. Since the OP wants to interface the detector to a computer, it's likely that the 5VDC would be available there. Or a \$.50 5V wall-wart from Goodwill. And where did the "relay" come from? The output is an isolated logic level signal.

Ken

Status
Not open for further replies.