I would like to turn on the vacuum cleaner every time I start the
saw/sander/whatever. It's not a specialised cleaner - just a Henry.

ISTR current operated gadgets for this - a multi way socket strip which
energises all the sockets if current is drawn from a 'master' one....

Anyone have any information/places to get them please?

--
Bob Eager
begin a new life...dump Windows!

"Bob Eager" wrote in message
...
I would like to turn on the vacuum cleaner every time I start the
saw/sander/whatever. It's not a specialised cleaner - just a Henry.

ISTR current operated gadgets for this - a multi way socket strip which
energises all the sockets if current is drawn from a 'master' one....

Anyone have any information/places to get them please?

Lidl had these on sale a couple of months ago at £6.99 each. Picked up a few
for my computers, but had to return one only after a few weeks. The rest
seems to be behaving for now.

On Sun, 23 Jan 2005 23:56:21 -0000, "clueless2" no.spam wrote:

Lidl had these on sale a couple of months ago at £6.99 each.

Won't work for machine tools though. The current, particularly the
inrush on startup, will kill them if you use anything bigger than a
detail sander.

If you have to do it with parts from Lidl, then try their
remote-controlled sockets. £15 for four and a radio remote control, so
you can even afford to kill the odd one ! Having _remote_ control of
the dust collector is nearly as good as having automatic control.

Another way is some good ear defenders, so you don't worry so much
about turning it off.

If you know some electronics, then a surplus (or even new from RS)
current transformer and a simple circuit with a rectifier, op-amp and
monostable delay can drive a contactor (big relay) for you. Mine is
all junk-box parts. Don't forget that time delay to keep it running
after switch off, otherwise it doesn't clear the last few chips out.
--
Smert' spamionam

On 23 Jan 2005 22:27:36 GMT, Bob Eager wrote:

ISTR current operated gadgets for this - a multi way socket strip
which energises all the sockets if current is drawn from a 'master'
one....

Anyone have any information/places to get them please?

Seen in B&Q if Lide don't have any... but as others have pointed out
watch the ratings, though a decent CRT has quite an inrush as the
degaussing takes place.

CPC have a Velleman-kit module K8034 (CPC Part HK00779 =A315.97 + VAT)
but looking at the picture and the spec this has changed between the
2004 cat and 2005. Looks like the max loads are now lower. 2A for the
master and 5A for the slave, it uses a relay for the slave switching
though... It also says "enclosure supplied".

--
Cheers
Dave. pam is missing e-mail

On Mon, 24 Jan 2005 09:50:58 -0000, "Christian McArdle"
wrote:

Or you can simply run the contactor from the flimsy autostart device.

No, a woodworking machine (especially with a brush motor) will kill
the sensing circuit in the Lidl auto-extension lead.

Most DCs that are switched on and off, rather than permanentyly
plumbed and running continuously, are just quite small induction
motors of 1/3rd or 1/2 horse. It might manage to survive those
(marginal, but probable).

Andy Dingley wrote:
On Mon, 24 Jan 2005 09:50:58 -0000, "Christian McArdle"
wrote:

Or you can simply run the contactor from the flimsy autostart device.

No, a woodworking machine (especially with a brush motor) will kill
the sensing circuit in the Lidl auto-extension lead.

There is a 2A fuse inside the Lidl thing.
Unfortunately, I couldn't see an obvious way to upgrade the sensor socket
to take 13A.

Simplest is take a relay, remove the winding and rewind it with thick
insulated cpper wire. Once a certain current goes through that, the
relay will close. You get around a 3:1 current operating range, which
should be workable for power tools. Relays typically close at around
half rated, and generally survive upto 1.5x rated.
It is best to calculate wire size.


NT

On Mon, 24 Jan 2005 10:11:33 UTC, "Dave Liquorice"
wrote:

CPC have a Velleman-kit module K8034 (CPC Part HK00779 œ15.97 + VAT)
but looking at the picture and the spec this has changed between the
2004 cat and 2005. Looks like the max loads are now lower. 2A for the
master and 5A for the slave, it uses a relay for the slave switching
though... It also says "enclosure supplied".

Thanks...didn't see that one when I looked! May be useful in the
future...

--
Bob Eager
begin a new life...dump Windows!

On 24 Jan 2005 18:01:22 GMT, Ian Stirling
wrote:

Andy Dingley wrote:
On Mon, 24 Jan 2005 09:50:58 -0000, "Christian McArdle"
wrote:

Or you can simply run the contactor from the flimsy autostart device.

No, a woodworking machine (especially with a brush motor) will kill
the sensing circuit in the Lidl auto-extension lead.

There is a 2A fuse inside the Lidl thing.
Unfortunately, I couldn't see an obvious way to upgrade the sensor socket
to take 13A.

Hi,

Use the Lidl thing to drive a mains coil relay, something like RS
352-474 will do.

cheers,
Pete.

On Mon, 24 Jan 2005 23:01:53 +0000, Pete C
strung together this:

Use the Lidl thing to drive a mains coil relay, something like RS
352-474 will do.

No, it's the sensor socket that is under-rated. That's the one that
the powertool plugs into.
--

SJW
Please reply to group or use 'usenet' in email subject

Relays cost around =A31-2 a piece, or for 24v you can find them in
various chucked out kit. Try to avoid rat shack etc.


NT

For jobs like the vacuum cleaner/circular saw combination, you could
make your own gadget if you're so inclined ( and this is a DIY forum
after all ).

If you get a reed switch ( glass tube with a magnetically sensitive
switch inside ) you can wind a number of turns of suitably rated wire
around it and place it in series with the master load.

When the current flows, the reed relay closes and in turn operates a
more powerful relay that works the vac.

Reed switches typically need about 30 amp/turns to operate, so if your
saw draws 3 amps then 10 turns will do the trick. You can't harm a reed
switch by exposing it to too much of a magnetic field, but they are
very puny switches in an electrical sense, so make sure you get one
that will handle the voltage and current needed for your chosen power
relay ( the one that works the vac ). It's most unlikely that you'll
find a reed switch that will work a vac directly without needing
another power relay.

On Mon, 24 Jan 2005 23:14:31 +0000, Lurch
wrote:

On Mon, 24 Jan 2005 23:01:53 +0000, Pete C
strung together this:

Use the Lidl thing to drive a mains coil relay, something like RS
352-474 will do.

No, it's the sensor socket that is under-rated. That's the one that
the powertool plugs into.

Doh! :|

In article .com,
Roly wrote:
If you get a reed switch ( glass tube with a magnetically sensitive
switch inside ) you can wind a number of turns of suitably rated wire
around it and place it in series with the master load.

When the current flows, the reed relay closes and in turn operates a
more powerful relay that works the vac.

Are you saying a reed switch will work with AC?

--
*Why is 'abbreviation' such a long word?

Dave Plowman London SW
To e-mail, change noise into sound.

On 25 Jan 2005 07:53:48 -0800, wrote:

but they are very puny switches in an electrical sense, so make sure
you get one that will handle the voltage and current needed for your
chosen power relay

And protect it from the back EMF from the relay coil when it switches
off. There is no switch off delay with this either, which your really
do need for vac to clear the last lot of chips/dust WHY.

--
Cheers
Dave. pam is missing e-mail

On 25 Jan 2005 07:53:48 -0800, wrote:

It's most unlikely that you'll
find a reed switch that will work a vac directly without needing
another power relay.

Hard to find now, but they do exist - look for one with mercury wetted
contacts.

Check out CPC's catalogue ( page 2479 )

They have a range of reed switches rated up to 3A or 1500V ac, however
the maximum VA is only 120, which is why you need a power relay for the
vac, but to operate a power relay, you only need a lesser reed relay,
which costs 68p. I would expect Maplin & RS to offer a similar range.

I use this reed relay trick to operate an extractor fan in a utility
room where an old unvented tumble drier is located. Turn on the drier
and the fan automatically turns on as well, but the fan can be run
independently too if you wish.

I couldn't think of a simpler solution.

Don't think it matters. ;-) I've got loads of assorted reed relays
and
they're all DC only.

good point. Reed relays will typically switch upto a few hundred hertz.
Although the bigger relay may not be too bothered by a chopped feed, it
will reduce the life of the reed dramatically.


I'd rectify the feed to the reed and add a reservoir cap: this will
also give run on after power off, as wanted by so many.

A small cap across the ac terminals of the 4 diode brisge will protect
it against most spikes.


NT

wrote:
Check out CPC's catalogue ( page 2479 )

They have a range of reed switches rated up to 3A or 1500V ac,
however
the maximum VA is only 120, which is why you need a power relay for
the

That's the contact rating.

I think the question was do they work with an Alternating field as you
would get by winding mains supply to a power tool around one?

MBQ

wrote:
Don't think it matters. ;-) I've got loads of assorted reed relays
and
they're all DC only.

good point. Reed relays will typically switch upto a few hundred
hertz.
Although the bigger relay may not be too bothered by a chopped feed,
it
will reduce the life of the reed dramatically.


I'd rectify the feed to the reed and add a reservoir cap: this will
also give run on after power off, as wanted by so many.


How do you rectify the feed to the reed? It's a magnetic field from a
few turns of the supply wire to the load?

If you wanted a steady feed, then I guess you could put a power diode
in series with the coil and a similar one the opposite way round across
the coil and first diode. The one in my utility room hasn't been told
about that sort of luxury and just keeps on working.

I've also seen systems that use about three suitably rated silicon
diodes in series in line with the live feed ( presumably with reverse
diodes across them to provide the path for the opposite polarity.

As each diode drops about a volt, you'll get 3V dropped across the
three of them. That's enough to operate an LED plus limiting resistor.
Obviously the master load will receive a slightly lower operating
voltage than usual.

In reality, the LED will actually be part of an opto-triac which will
switch the slave power when the master load operates.

I tried to make a similar system for an A/V system once, but the
standby current ensured it never switched off and I had to use a
different solution.

On Tue, 25 Jan 2005 15:53:48 UTC, wrote:

If you get a reed switch ( glass tube with a magnetically sensitive
switch inside ) you can wind a number of turns of suitably rated wire
around it and place it in series with the master load.

When the current flows, the reed relay closes and in turn operates a
more powerful relay that works the vac.

That sounds feasible. However, as someone mentioned, I also need a time
delay before the vac goes off!
--
Bob Eager
begin a new life...dump Windows!

How do you rectify the feed to the reed? It's a magnetic field from a
few turns of the supply wire to the load?

Put it thourhg bridge rectifier, ensuring its rated to take surge
current and voltage spikes.

NT

On 26 Jan 2005 22:27:41 GMT, "Bob Eager" strung
together this:

If you get a reed switch ( glass tube with a magnetically sensitive
switch inside ) you can wind a number of turns of suitably rated wire
around it and place it in series with the master load.

When the current flows, the reed relay closes and in turn operates a
more powerful relay that works the vac.

That sounds feasible. However, as someone mentioned, I also need a time
delay before the vac goes off!

Get a delay off timer as well then. I'm sure ther'll be one in the CPC
kits, or butcher an electronic time lag switch.
--

SJW
Please reply to group or use 'usenet' in email subject

In article . com,
wrote:
How do you rectify the feed to the reed? It's a magnetic field from a
few turns of the supply wire to the load?

Put it thourhg bridge rectifier, ensuring its rated to take surge
current and voltage spikes.

I'm confused. The original idea was to use the winding on the reed 'relay'
to current sense. If you start introducing diodes, surely this will effect
the supply to the device you're sensing? Unless you use a shunt resistor
and sense off that via a rectifier.

--
*60-year-old, one owner - needs parts, make offer

Dave Plowman London SW
To e-mail, change noise into sound.

I'm confused. The original idea was to use the winding on the reed
'relay'
to current sense. If you start introducing diodes, surely this will
effect
the supply to the device you're sensing? Unless you use a shunt
resistor
and sense off that via a rectifier.


The only effect on the load item is 2 diode drops, ie about 2v. The
load still gets ac, its only the reed thats sees dc.

I'll see if i can draw it...


OK... you replace this:

______________
)
) reed relay coil
)
)
______________)



with this:

____________
+ /\ )
/ \ )
________/ BR \___ ) reed relay coil
~ \ / ~ | )
\ / | )
- \/____ | ____)
|
_________________|



BR is a bridge rectifier, 4 diodes.
Also add a cap across the reed coil to stop it buzzing at 100Hz.


NT

On 27 Jan 2005 15:19:33 -0800, wrote:

I'll see if i can draw it...

Might have looked OK on your screen but it was rubbish on mine. If you
are going to "draw" somthing use a fixed pitch font and don't use tabs
only spaces.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:
wrote:

I'll see if i can draw it...

Might have looked OK on your screen but it was rubbish on mine. If
you
are going to "draw" somthing use a fixed pitch font

i did

and don't use tabs
only spaces.

i did, im not a dummy. Looks like google beater stripped out all the
leading spaces.

Lets try again: And if it doesnt work tough ****.


OK... you replace this:

______________
)
) reed relay coil
)
)
______________)

with this:

____________
+ /\ )
/ \ )
________/ BR \___ ) reed relay coil
~ \ / ~ | )
\ / | )
- \/____ | ____)
|
_________________|


BR = bridge rectifier

hmm, sorry for being rude :/ i was in a right grump over something.

NT

On 29 Jan 2005 04:12:46 -0800, strung together
this:

hmm, sorry for being rude :/ i was in a right grump over something.

Could it be that you use Google?
--

SJW
Please reply to group or use 'usenet' in email subject

If anybody hasn't been able to work out that ASCII diagram, I'll try
with words.

He suggests using a suitably rated bridge rectifier. They have four
connections, labelled plus, minus and two marked with the AC symbol ~

The idea is to connect the reed coil and smoothing capacitor across the
plus and minus.

One AC terminal connects to the incoming mains while the other AC
terminal is the connection to the load. This arrangement interrupts the
live connection to the load.

In article .com,
writes:
If anybody hasn't been able to work out that ASCII diagram, I'll try
with words.

He suggests using a suitably rated bridge rectifier. They have four
connections, labelled plus, minus and two marked with the AC symbol ~

The idea is to connect the reed coil and smoothing capacitor across the
plus and minus.

I kind of doubt a smoothing capacitor would work with what is
essentially a neglibable impeadance load; there's negligable voltage
to charge it up and very low impeadance to discharge it instantly.
The capacitor would have to be enormous (but could be very low
operating voltage). With no smoothing capacitor, there's no point
in the bridge rectifier.

--
Andrew Gabriel

Well, yes. But you'll end up with rectified mains. Which will fry any
reed
relay I've ever seen.

This shows the trouble with asking a tronics question on a non-tronics
newsgroup.

NT

On Mon, 31 Jan 2005 00:05:46 +0000 (GMT), Dave Plowman (News) wrote:

Well, yes. But you'll end up with rectified mains. Which will fry
any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

What Mr Gabriel said about the smoothing C is true though. It
effectively has a dead short across it through the coil windings.

I guess you could add a series R and up the number of turns to
compenstate for the lower I or maybe just upping the turns and using
much thinner wire for the coil would do it?

--
Cheers
Dave. pam is missing e-mail

In article om,
Dave Liquorice wrote:
Well, yes. But you'll end up with rectified mains. Which will fry
any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

I'm talking about the coil. Haven't seen any high voltage ones.

--
*If you lived in your car, you'd be home by now *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article om,
Dave Liquorice wrote:
Well, yes. But you'll end up with rectified mains. Which will fry

any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

I'm talking about the coil. Haven't seen any high voltage ones.
The coil doesnt see high voltage, youve misunderstood the scheme.

NT

On Mon, 31 Jan 2005 11:06:46 +0000 (GMT), Dave Plowman (News) wrote:

Well, yes. But you'll end up with rectified mains. Which will fry
any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

I'm talking about the coil. Haven't seen any high voltage ones.

Ah I wasn't using a preassembled jobbie but a true DIY affair with a
home made coil as suggested a while back. Most reeds need around 20AT
to operate so for a 500W load at mains voltage gives 2A or there
abouts. So 20 or less turns for the current detection easy enough with
some 1 or 1.5mm^2 enameled wire. Might have to be careful not to wind
the coil to tight so as not to crack the enamel.

--
Cheers
Dave. pam is missing e-mail

wrote:
Dave Plowman (News) wrote:
In article om,
Dave Liquorice wrote:
Well, yes. But you'll end up with rectified mains. Which will
fry

any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

I'm talking about the coil. Haven't seen any high voltage ones.
The coil doesnt see high voltage, youve misunderstood the scheme.

But it does have to handle the full operating current (and any startup
transients) of the load.

MBQ

wrote:
Dave Plowman (News) wrote:
In article om,
Dave Liquorice wrote:
Well, yes. But you'll end up with rectified mains. Which will
fry

any reed relay I've ever seen.

Er, how? The reed contacts are not in this circuit only the coil
around it...

I'm talking about the coil. Haven't seen any high voltage ones.
The coil doesnt see high voltage, youve misunderstood the scheme.


But will need to handle the full current of the load.

MBQ

Some people appear to be unaware that the custom-wound reed coil is
acting as a current operated rather than a voltage operated relay. Just
like an ammeter, it's wired in series with the load.

When I made mine, the reed was about 50mm long and I calculated that
I'd need around 12 turns at the expected load.

I didn't use enamelled wire, but instead used PVC insulated wire of an
appropriate cross section.

On further consideration, I think enamelled wire would have been OK as
there will only be a small potential difference across it, but I didn't
think of that at the time. I had the PVC wire already and there was
plenty of room to wind it.