Current Sensor For BS2 Project

KatyBri

I am working on a BS2 project which needs to determine when some household appliances are ON.

Does anyone have experiance with a circuit or device that would simply determine when current is flowing in the appliance's 120 VAC power cord? I am not interested in knowing how much current is flowing, only that some is so that I can then condition the device/circuit to send a logic 0 or 1 voltage level to the BS2 pins.

Thanks

Tom Walker

Put a small light bulb in series parallel·(with ALL due safety precautions) and use a photodetector, maybe?

Clamp-on ammeter...

Just a couple of ideas...

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Post Edited (Tom Walker) : 9/29/2006 1:15:36 PM GMT

PJAllen

· There are a lot of AC-powered items which are "on" (i.e. drawing current) all the time -- even when they're "off".· It's not uncommon for the transformer primary to be "on" all the time, lots of times the appliance, if it has a switch, switches the secondary "on"/"off".·

· So, you need to·determine if the appliance/s or whatever is to be monitored really DOES turn totally "off" (primary/Mains/120 off), real OFF.· If it's so, then you could use a neon lamp wired in PARALLEL (not in series) with the switched side and couple that to a photo-resistor.

· [noparse][[/noparse]You've asked about this before, yes?· It would have been better to have "re-introduced" your original post using your own update.]

metron9

I think you can make your own Ammeters to monitor AC circuits without directly connecting to the AC line.
Tom suggested a clamp-on-ammeter. A current flowing through a wire creates a magnet field. This field can be measured by wrapping the wire around a metal object. The current flowing through the wire creates a voltage you can measure. A transformer uses magnetic field to transfer electric current through a magnetic field, this is similar to the way an ammeter works, (I think).

Look up ammeter and how they work, I would think you are looking at a strip plug design like modifying a typical AC power strip. Connecting each plug receptical to an ammeter using some kind of wire wrapping to measure that magnetic field. You would then need an ADC to convert the voltage for each receptical to digital.

I am not sure if wrapping say for example a thin insulated wire a few inches around a wire (picture1) will give a voltage or if you have to use something like the peak interrupter (picture2). This unit measures the current of electric heat units and drives an electric meter that shows how many KWhours I use to heat my house.

AS PJ said, you may have to get a base line reading with the units plugged in for each unit you are measuring as electronic components in AC devices are typically in a standby mode using some current or you could use a minimum current threshold for all of them I would think, where that point is would have to be determined by the devices.

Remember there are some very strict safety rules required when interfacing AC power and low voltage wiring within that same housing to prevent both electrical shock hazards and fire hazards.

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Tom Walker

metron9,
You are absolutely right...the lamp should be in parallel...too many projects being "percolated" at the same time so I wasn't focused on what I was writing. I have edited my previous post.

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Truly Understand the Fundamentals and the Path will be so much easier...