DC pulse from a mains load?

Also VCR heads. several megahertz bandwidth, but kind of fragile.

--
  When I tried casting out nines I made a hash of it.
Reply to
Jasen Betts
Loading thread data ...

They would be slow, audio range if that.

Try maybe 10 turns of secondary on a ferrite toroid, into a 50 ohm scope. That can be a 100 MHz current probe.

--
John Larkin   Highland Technology, Inc   trk 

jlarkin att highlandtechnology dott com 
 Click to see the full signature
Reply to
John Larkin

Yes, the aim is to detect when a lamp is switched on. But presumably AC voltage would *only* be present (at least in the Live wire) when power is applied via the relay at A?

Background info: I have a remote control circuit in corner A of the lounge. Amongst other things it allows me to switch on a lamp L1 in corner B, via a mains cable between A and B, which I placed years ago before carpet was laid on top. There's also a standard mains power socket at B. I have a second lamp L2 close to B, which I now also want to add to my control repertoire. But it's impractical to place any more wires between A and B, even a thin DC-carrying pair.

So my idea is to detect when L1 is switched briefly on and off, within say 1 second, and use the resultant two DC pulses as input to appropriate logic (yet to be designed!) to toggle power to L2. The brief illumination of L1 would be an acceptable flaw.

I first thought of an LDR close to L1 but, apart from the inconsistent light levels in the room, my other LDR circuits have all suffered from long term unreliability caused by changes in LDR characteristics. That said, maybe there *is* a reliable and simple light-based sensor circuit I could try?

As soon as I get seasonal chores etc out of the way I'll get into the shed workshop and start experimenting with the neat ideas suggested here, for which many thanks.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Easier to just use 2 diodes. One diode at the controlling end sends +110/240, the other switch sends -110/240. Relays at other end have a diode & C each.

NT

Reply to
tabbypurr

I've used cheap surface-mount unshielded power inductors as mag field sources and detectors, for near-field data transmission and power transfer. I designed an electric meter that used that. It was for a country with unreliable power, so the meter reader guy could power up and read out the meter even with the mains power off.

You can make a very high voltage isolator by putting dumbell-type inductors on opposite sides of a PCB.

--
John Larkin   Highland Technology, Inc   trk 

jlarkin att highlandtechnology dott com 
 Click to see the full signature
Reply to
John Larkin

Oh! ... that makes it so much simpler. Light L1 is plugged into the end of this under-carpet cable - insert a short extension cord between them and tap this cord. The tap gives you AC when L1 is turned on & you can manipulate it as you desire. Most simply would be to drive a latching AC relay.

Reply to
Bob Engelhardt

Sorry, I don't understand, can you clarify your solution please?

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Thanks, but If I understand you correctly you're suggesting cutting the current mains cable which goes (directly) to L1 near corner B (so it's a solution in the 'cut-the-wires' category) and then somehow getting the DC pulses I need for my L2 toggle circuit ("...manipulate it as you desire.").

Isn't that effectively a re-statement of my question? It's the 'manipulation' on which I'm seeking advice.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

Divide the control end switch into 2 switches, one sends the mains +ve pulses, the other sends the -ve ones. Only when they're both on does it deliver the full mains waveform. CFLs & a large number of LEDs are happy with that.

NT

Reply to
tabbypurr

No, not cut. I assume that L1 is not hard-wired to the under-carpet cable. But the cable has a connector that L1 is plugged into. If it is hard-wired, never mind.

If it is plugged in (as I said previously), unplug it, plug an extension into the cable, and plug L1 into the extension. Also plug another cord into the extension and use that cord to control L2. Your original post asked for the "...simplest safe circuit ..." & that would be a latching relay.

---cable---

Reply to
Bob Engelhardt

Some convector heaters use this method for signalling between a timeswitch and multiple radiators. They use an extra live wire "pilot wire" with four states: off, on, +ve half wave rectified and -ve half-wave rectified.

It seems to work well.

John

Reply to
jrwalliker

pulses, the other sends the -ve ones. Only when they're both on does it del iver the full mains waveform. CFLs & a large number of LEDs are happy with that.

h

You can do it without an extra wire. The signal & power wires are the same one. To avoid flicker you need to add a little capacitance at the end. If f or some reason you wanted to you could even choose the C to maintain compat ibility with a wanted load of filament lamps, though there seems little rea son to these days.

NT

Reply to
tabbypurr

Reply to
Terry Pinnell

Sorry, forgot to include the link:

formatting link

Reply to
Terry Pinnell

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.