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DC pulse from a mains load?

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John Larkin
Guest

Thu Dec 27, 2018 12:45 am   



On Wed, 26 Dec 2018 16:05:29 -0500, bitrex <user_at_example.net> wrote:

Quote:
On 12/26/2018 11:10 AM, John Larkin wrote:
On Wed, 26 Dec 2018 03:03:01 -0800 (PST), Klaus Kragelund
klauskvik_at_hotmail.com> wrote:

Mains wire goes through the toroid hole ?

Just a pickup coil near the wires will sense current. No need to
disturb the power wiring.

A drum core inductor is a simple pickup.


A rectangular slab of copper-clad FR4 on ether side of the wire will
probably work OK as a pickup/sensor, it's cheap


If the power wires aren't shielded, like in a conduit, an
electrostatic pickup is fine. Wrap an insulated wire around the power
conductors. Some oscilloscopes do that to pick off the line trigger.

I have seen an instrument that clamped the hot/black wire against a PC
board to get the line trigger without making a direct line connection.

https://www.dropbox.com/s/08yw617mrv5tvfg/AC_Pickoff.JPG?dl=0

But if the OP wants to sense a load, he needs to measure current, so
needs a magnetic pickup.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

amdx
Guest

Thu Dec 27, 2018 12:45 am   



On 12/26/2018 4:30 PM, Cursitor Doom wrote:
Quote:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Playback heads have a nice pointed sensitivity range
http://panteltje.com/pub/play_back_head_current_sensor_img_1153.jpg

Is that a xtal I see hiding under that grey goop?




You missed the point, Panteltje used a audio tape recorder head to
sense current through a wire, he then amplified the signal.
I believe he also said he just ran the unseparated pair (white wire
pair) near the head and because the head response area is quite small it
responds to the closest wire without any problem from the second wire.
As he explained it, "a nice pointed sensitivity range"
Probably should start saving audio heads, I think they're use may be
dwindling.
Mikek

Cursitor Doom
Guest

Thu Dec 27, 2018 2:45 am   



On Wed, 26 Dec 2018 14:32:39 -0800, Lasse Langwadt Christensen wrote:

Quote:
onsdag den 26. december 2018 kl. 23.31.00 UTC+1 skrev Cursitor Doom:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Playback heads have a nice pointed sensitivity range
http://panteltje.com/pub/play_back_head_current_sensor_img_1153.jpg

Is that a xtal I see hiding under that grey goop?


looks like a tape head


I thought the 'C' shaped thing around the blue resistor was the actual
current sensor? Maybe Jan will deign to inform us in due course.



--
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the Usenet protocol. Reproduction in whole or part through other
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protocols constitutes acceptance of this condition.


Guest

Thu Dec 27, 2018 9:45 am   



On a sunny day (Wed, 26 Dec 2018 22:26:37 -0000 (UTC)) it happened Cursitor
Doom <curd_at_notformail.com> wrote in <q00v6t$i0j$1_at_dont-email.me>:

Quote:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Nope, as you can see from the picture,
and in that setup I used it to measure current draw from a normal 2 wire
mains lead,
output to ADC.
Used for years.

Sounds like these heads could make good improvised current probes for
oscilloscopes. It took me ages to find a decent Tektronix 'scope current
probe and I had to pay through the nose for it, too.
For larger currents, though, I got some of these and they work -
surprisingly - really well!

https://www.ebay.co.uk/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-
Clamp-Sensor-30A-Good/141679460958?
hash=item20fcc1025e:g:pGYAAOSwpDdVZ82w:rk:9:pf:0


Good price!
is it not simpler to show the link as:
https://www.ebay.co.uk/itm/141679460958
then nobody has to be scared of alien website redirects.

the /itm/xxxxx where xxx is the item number.


As to the playback head, yes, but remember the induced voltage goes up with frequency etc.
You will likely need some correction (like in a tape playback amplifier)
I think I played with that,

We used a signal generator with a single wire in front of the head to calibrate the playback amplifier frequency correction
for the perfotapes.
Had to be done every now and then.
Sixties.


The reason the wire is glued in position is, think of the width of a stereo head track,
fraction of a cassette tape width.


I do not have all those expensive things or antiques like some here,
technology had advanced, yes I used Avo in the past, but never longed back.
Well I still have my old Trio analog scope from the seventies, it still works.


Guest

Thu Dec 27, 2018 9:45 am   



On a sunny day (Wed, 26 Dec 2018 22:30:56 -0000 (UTC)) it happened Cursitor
Doom <curd_at_notformail.com> wrote in <q00vf0$i0j$2_at_dont-email.me>:

Quote:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Playback heads have a nice pointed sensitivity range
http://panteltje.com/pub/play_back_head_current_sensor_img_1153.jpg

Is that a xtal I see hiding under that grey goop?


No, that is the head,
the 'grey goop' is 2 compoment glue to prevent the wire from moving.

Jasen Betts
Guest

Thu Dec 27, 2018 9:45 am   



On 2018-12-26, Cursitor Doom <curd_at_notformail.com> wrote:
Quote:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Nope, as you can see from the picture,
and in that setup I used it to measure current draw from a normal 2 wire
mains lead,
output to ADC.
Used for years.

Sounds like these heads could make good improvised current probes for
oscilloscopes. It took me ages to find a decent Tektronix 'scope current
probe and I had to pay through the nose for it, too.
For larger currents, though, I got some of these and they work -
surprisingly - really well!

https://www.ebay.co.uk/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-
Clamp-Sensor-30A-Good/141679460958?
hash=item20fcc1025e:g:pGYAAOSwpDdVZ82w:rk:9:pf:0


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

--
When I tried casting out nines I made a hash of it.

John Larkin
Guest

Thu Dec 27, 2018 6:45 pm   



On Wed, 26 Dec 2018 22:26:37 -0000 (UTC), Cursitor Doom
<curd_at_notformail.com> wrote:

Quote:
On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Nope, as you can see from the picture,
and in that setup I used it to measure current draw from a normal 2 wire
mains lead,
output to ADC.
Used for years.

Sounds like these heads could make good improvised current probes for
oscilloscopes. It took me ages to find a decent Tektronix 'scope current
probe and I had to pay through the nose for it, too.


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.


Quote:
For larger currents, though, I got some of these and they work -
surprisingly - really well!

https://www.ebay.co.uk/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-
Clamp-Sensor-30A-Good/141679460958?
hash=item20fcc1025e:g:pGYAAOSwpDdVZ82w:rk:9:pf:0


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Terry Pinnell
Guest

Thu Dec 27, 2018 7:45 pm   



John Larkin <jjlarkin_at_highlandtechnology.com> wrote:

Quote:
On Wed, 26 Dec 2018 16:05:29 -0500, bitrex <user_at_example.net> wrote:

On 12/26/2018 11:10 AM, John Larkin wrote:
On Wed, 26 Dec 2018 03:03:01 -0800 (PST), Klaus Kragelund
klauskvik_at_hotmail.com> wrote:

Mains wire goes through the toroid hole ?

Just a pickup coil near the wires will sense current. No need to
disturb the power wiring.

A drum core inductor is a simple pickup.


A rectangular slab of copper-clad FR4 on ether side of the wire will
probably work OK as a pickup/sensor, it's cheap

If the power wires aren't shielded, like in a conduit, an
electrostatic pickup is fine. Wrap an insulated wire around the power
conductors. Some oscilloscopes do that to pick off the line trigger.

I have seen an instrument that clamped the hot/black wire against a PC
board to get the line trigger without making a direct line connection.

https://www.dropbox.com/s/08yw617mrv5tvfg/AC_Pickoff.JPG?dl=0

But if the OP wants to sense a load, he needs to measure current, so
needs a magnetic pickup.


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


Guest

Thu Dec 27, 2018 7:45 pm   



On Thursday, 27 December 2018 17:51:03 UTC, Terry Pinnell wrote:

Quote:
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


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

John Larkin
Guest

Thu Dec 27, 2018 9:45 pm   



On Thu, 27 Dec 2018 07:46:11 GMT, <698839253X6D445TD_at_nospam.org>
wrote:

Quote:
On a sunny day (Wed, 26 Dec 2018 22:30:56 -0000 (UTC)) it happened Cursitor
Doom <curd_at_notformail.com> wrote in <q00vf0$i0j$2_at_dont-email.me>:

On Wed, 26 Dec 2018 18:47:24 +0000, 698839253X6D445TD wrote:

Playback heads have a nice pointed sensitivity range
http://panteltje.com/pub/play_back_head_current_sensor_img_1153.jpg

Is that a xtal I see hiding under that grey goop?

No, that is the head,
the 'grey goop' is 2 compoment glue to prevent the wire from moving.


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
http://www.highlandtechnology.com

Bob Engelhardt
Guest

Fri Dec 28, 2018 12:45 am   



On 12/27/2018 12:50 PM, Terry Pinnell wrote:
Quote:

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. ...


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.

Terry Pinnell
Guest

Fri Dec 28, 2018 1:45 pm   



Bob Engelhardt <BobEngelhardt_at_comcast.net> wrote:

Quote:
On 12/27/2018 12:50 PM, Terry Pinnell wrote:

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. ...

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.


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

Terry Pinnell
Guest

Fri Dec 28, 2018 1:45 pm   



tabbypurr_at_gmail.com wrote:

Quote:
On Thursday, 27 December 2018 17:51:03 UTC, Terry Pinnell wrote:

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

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


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

Terry, East Grinstead, UK


Guest

Fri Dec 28, 2018 1:45 pm   



On Friday, 28 December 2018 12:01:51 UTC, Terry Pinnell wrote:
Quote:
tabbypurr wrote:
On Thursday, 27 December 2018 17:51:03 UTC, Terry Pinnell wrote:

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

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

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

Terry, East Grinstead, UK


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


Guest

Fri Dec 28, 2018 2:45 pm   



On Friday, 28 December 2018 12:40:24 UTC, tabb...@gmail.com wrote:

Quote:
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.

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

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