contactless 230v ac sense - Page 1
Forum section: electronics / projects

author: gmankev
author_rank: Newbie
timestamp: December 26, 2018, 05:12:04 pm
content: I need a circuit which we clip to insulated mains cables to detect there is 230v mains ac present. I dont need to measure the flow of current, just that the cable is powered. I am not allowed cut the cable, elsewhere I do have access to mains GND. SO a asimple circuit that exploits very low AC currentto flow through this airgap will work . I see various test tools do this. I see sample circuits online that can do it (https://www.pocketmagic.net/mains-hum-sensor/) .Might there be a cheap sensor with integrated signal amplification in reasonable housing that can do this and return discrete current or voltage indicating mains is present.

author: soldar
author_rank: Super Contributor
timestamp: December 26, 2018, 05:40:02 pm
content: What are you trying to achieve? You are trying to identify the live-phase conductor as opposed to the neutral or ground? How close can you get to the conductor? You can get right up to the wire insulation but not through it, right? So we are talking about 1 or 2 mm insulation barrier? In that case a capacitive coupling should work.

author: Ian.M
author_rank: Super Contributor
timestamp: December 26, 2018, 06:44:45 pm
content: You'll have a lot of problems with the cable geometry.Flat cable has two possible positions for Line and Neutral,depending on its orientation, so you need a sensor with an independent pickup at each edge. Round cable may have a ground wire, so less than half of its circumference at any point will effectively trigger the sensor, as there will little external E field over the sector screened by the Ground and Neutral conductors. Armoured and shielded cables wont have a detectable external E field as its fully screened by the ground conductor.

author: soldar
author_rank: Super Contributor
timestamp: December 26, 2018, 06:58:17 pm
content: It is different if you are trying to check if an individually accessible wire in a tray or cabinet is energized that to check if a single wire of a multicable bunch is energized. Still, it should be possible to know if a cable is energized but you will not know the individual conductor as they are not identifiable from outside. I have sometimes built a prick tool with a pin so I could make contact with the conductor but after I remove the pin the plastic insulation covers the wire again. I am talking of the tiny pins used for sewing. When I have a length of cable which is broken somewhere I can quickly use the prick to test it in several places and determine the location of the fault.

author: gmankev
author_rank: Newbie
timestamp: December 27, 2018, 02:23:01 am
content: We are doing a piece of monitoring equipment and we must tell if the consumer equipment we are connected to is connected to its mains voltage.. For ease of use, we dont want to connect to any of the mains terminals, which are behind access panels. The mains conductor is a standard flexible cable with L,N and E all of 1.5mm . So if I touch the insulated mains cable, I could be between 2 and say 4 mm from the active live. Yes capacitive coupling works, well at least evidenced by those simple mains detection pens.I had figured there might be a simple packaged circuit already available that would work reliably and have suitable signal amplification and perhaps rejection of AC that might be coupled in close by cables close to mine. It might need also a reference to ground in the equipment, which we have easily.. However a search only turns up such pens, or clamp on amp meters (which as there is no current flowing and I have both connectors in a bundle will not work).