sensing 240V without touching the wires!

[mark.duyvesteyn]

how could i get a picaxe to sense the wether or not current is flowing along a 240 volt extension cord or similar without using the actual live wires? Im not concerned about the value, just a simple on or off.

Would using a small coil or wire in close proximity induce a voltage?

Thanks for any ideas/suggestions you can give me

 

[manuka]

Gidday Mark- I guess you are up with clamp meters? The old Red Shed sells a magnificent one at ~NZ$24 in fact. Sparkies use associated devices that may help ( some akin to a glorified neon tester), but for electromag. current sensing you'll strictly of course need to check just a single wire ( Phase or Neutral), rather than the whole cable. It rather depends on the mains current flowing, but a sense coil with few dozen fine wire turns will pick up a few mV (AC). Prior to energy meters turning up cheaply I explored this using automotive spark plug pickup units & split ferrite cores, & recall 10s-100s of mV (AC) were induced.

You may also have some mileage using a DS18B20 detecting the small temp rise associated with the mains current flow. This latter approach would be subject to thermal lag of course- how immediately do you need to know about things? Fellow Kiwi Stan.

 

[eclectic]

@Mark

Something like this one.
http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Test-Equipment/Analysers-Testers-Counter/AC-Voltage-detector/72881/kw/voltage+detector

You can easily remove the indicator LED,
and use the voltage to trigger the Picaxe.

e

 

[Andrew Cowan]

EPE magazine had an article recently about making a clamp on current sensor. It used a hall effect IC.

A

 

[pilko]

Do you want to sense voltage or current,they require different technology?