[Wildly OT] Manual on/off switch with electrical off-trip?
Andrew Stephenson
ventilation safety system. Have searched the net with google and
asked people who know people... Nada. This seems to be Bleeding
Edge Tech. :-( You guys and guyettes get around. May I ask you?
The device I seek is, basically, an ON/OFF switch with one set of
changeover contacts. A manual control (lever, &c) selects either
setting, while an electrical control (relay-type coil) lets ON be
tripped OFF by a 230V 50Hz (mains) pulse. Contacts should handle
5A mains but 10A would be good. Enclosed as for mounting in (eg)
a normally dry garage, where Questing Kiddiefingers are a hazard.
For the curious: this is part of a mechanical ventilation system.
If smoke or carbon monoxide is detected in the ducts, that switch
trips and shuts off the air flow until a human operator has had a
chance to hunt the cause. If mains fails NOT due to any smoke/CO
event, the system restarts when the mains returns. There is also
a sub-system of coloured status lights, local controls and noise-
makers round the house, simplifying panicking/shutoff/restarting.
TIA.
--
Andrew Stephenson
Phil Taylor
<am...@deltrak.demon.co.uk> wrote:
> I'm stumped in my search for a vital component in a planned house
> ventilation safety system. Have searched the net with google and
> asked people who know people... Nada. This seems to be Bleeding
> Edge Tech. :-( You guys and guyettes get around. May I ask you?
>
> The device I seek is, basically, an ON/OFF switch with one set of
> changeover contacts. A manual control (lever, &c) selects either
> setting, while an electrical control (relay-type coil) lets ON be
> tripped OFF by a 230V 50Hz (mains) pulse. Contacts should handle
> 5A mains but 10A would be good. Enclosed as for mounting in (eg)
> a normally dry garage, where Questing Kiddiefingers are a hazard.
If you are prepared to build it yourself, it would need only a couple
of relays and a mains switch. Put it in a sealed, earthed die-cast box
for safety. I'd need to draw a circuit diagram to explain how to make
it work, but it's not at all complicated. Let me know if you want
details.
Phil Taylor
Graham J
"Andrew Stephenson" <am...@deltrak.demon.co.uk> wrote in message
news:122046...@deltrak.demon.co.uk...
I'm sure I've seen devices like this for controlling machine tools. Usually
a recessed green button for ON and a large mushroom headed button for OFF.
Built-in overload sensing will trip it to off.
The issue is whether a remote signal will also trip it to off.
There may also be a difficulty that incoming mains is needed to hold the
switch on, so if the supply fails and returns, you must press the start
button.
--
Graham J
Phil Taylor
<gra...@nospam.zen.co.uk> wrote:
> I'm sure I've seen devices like this for controlling machine tools. Usually
> a recessed green button for ON and a large mushroom headed button for OFF.
> Built-in overload sensing will trip it to off.
>
> The issue is whether a remote signal will also trip it to off.
>
> There may also be a difficulty that incoming mains is needed to hold the
> switch on, so if the supply fails and returns, you must press the start
> button.
You don't need anything that complicated. A single relay is all that's
required, wired to make it self-latching so that once the control
voltage comes on it stays in the off position until the mains is
switched off and on again. It would cost about £15 quid for the
components to make it.
Phil Taylor
Andrew Stephenson
gra...@nospam.zen.co.uk "Graham J" writes:
> "Andrew Stephenson" <am...@deltrak.demon.co.uk> wrote in message
> news:122046...@deltrak.demon.co.uk...
> > I'm stumped in my search for a vital component in a planned house
> > ventilation safety system. [...]
> I'm sure I've seen devices like this for controlling machine
> tools. Usually a recessed green button for ON and a large
> mushroom headed button for OFF. Built-in overload sensing will
> trip it to off.
Yes, similar bells have been tinkling in my memory banks. Those
I have seen and been in a position to use have simply been fancy
switches, with emphasis on ease of killing the power in a panic.
> The issue is whether a remote signal will also trip it to off.
>
> There may also be a difficulty that incoming mains is needed to
> hold the switch on, so if the supply fails and returns, you
> must press the start button.
A conscious act of resetting by a human operator is essential, I
think. It must be possible for the source of the smoke/CO to be
searched out. Or, if none, for the system failure to be fixed.
The overcurrent/RCD trips made by (eg) MK combine a solid manual
lever that can be set ON/OFF (and, IIRC, something else) with an
electrical mechanism (solenoid, bimetallic strip?) that releases
stored mechanical energy to flip the switch OFF -- but not quite
the way I need.
FWIW, MK (and parent corp Honeywell) deny any ability to help.
Thanks, people, for having a go at this. If anyone comes across
somewhere that sells this kind of thing, I shall think kindly of
you for passing the word. I'm continuing to search. (Apple?!?)
--
Andrew Stephenson
Andrew Stephenson
not...@all.invalid "Phil Taylor" writes:
> In article <122046...@deltrak.demon.co.uk>, Andrew Stephenson
> <am...@deltrak.demon.co.uk> wrote:
>
> > I'm stumped in my search for a vital component in a planned house
> > ventilation safety system. [...]
>
> If you are prepared to build it yourself, it would need only a couple
> of relays and a mains switch. Put it in a sealed, earthed die-cast box
> for safety. I'd need to draw a circuit diagram to explain how to make
> it work, but it's not at all complicated. Let me know if you want
> details.
Ta for the offer but the simplest design I can think of (so far)
requires a mechanical component so that it has a memory of being
tripped. The design I have cooked up distinguishes shutdown due
to smoke/CO event and due to mains interruption.
I did toy with the notion of a relay held operated by mains that
is released by an event; but (a) that lacks a memory and (b) the
power it consumes, year after year, whilst not (yet) responding,
would add up; and this house is all about energy saving. :-)
The gadget would be close cousin to the trips modern houses have
in their "fuse" boxes, except that those respond to either over-
current or an RCD event. This needs a solenoid, as in a relay.
--
Andrew Stephenson
Andrew Stephenson
not...@all.invalid "Phil Taylor" writes:
I hope my explanations in my replies to each of you clarified why
a mechanical element is necessary in my application: power saving
over the long run, plus alarm "memory" even after mains failure.
The memory effect also discourages a system restart, should weird
stuff happen during a house fire -- cables shorting and restoring
power, &c. This is basic, no-mess, assume-bad-luck, engineering.
Lives could hang on getting it right. Or so I tell myself.
--
Andrew Stephenson
Andrew Stephenson
am...@deltrak.demon.co.uk "Andrew Stephenson" writes:
> I did toy with the notion of a relay held operated by mains that
> is released by an event; but (a) that lacks a memory and (b) the
> power it consumes, year after year, whilst not (yet) responding,
> would add up; and this house is all about energy saving. :-)
Sorry, should read "...that lacks the right kind of memory..." so
as to distinguish different causes of shutdown: smoke/CO vs brief
mains failure.
--
Andrew Stephenson
Phil Taylor
<am...@deltrak.demon.co.uk> wrote:
I see. Well, if you need something that holds it's state after being
tripped out, regardless of whether the power comes back on or not, you
need to use a mechanically latching relay. Those are a bit old
fashioned and hard to find now, and tend to be low voltage low power
devices. (They do, however, have a reputation for bomb-proof
reliability, which is what you need here.) It complicates the design a
little, but is still possible.
Phil Taylor
Adrian Tuddenham
> I'm stumped in my search for a vital component...
>
>...If mains fails NOT due to any smoke/CO
> event, the system restarts when the mains returns.
You need a magnetic latching relay which acts as a memory and can then
control a larger relay to handle the power switching etc. Once the
latch has operated, the relay will stay in one position until the
residual magnetism in its frame is cancelled by a current in the
opposite direction. The circuitry is slightly more complex than a
standard relay but it is absolutely fiddle-proof. I think they are
still a stock item from RS Components.
I have designed them into laboratory apparatus to protect the lives of
animals where I was unable to overrule unskilled 'reprogramming' of a
life support system. Once a certain bit of program had been executed
and the apparatuls left in a risky state, nothing on earth would make
the apparatus work again until the condition had been properly reversed.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Andrew Stephenson
not...@all.invalid "Phil Taylor" writes:
> In article <122054...@deltrak.demon.co.uk>, Andrew Stephenson
> <am...@deltrak.demon.co.uk> wrote:
>
> > [discussion]
> I see. Well, if you need something that holds it's state after being
> tripped out, regardless of whether the power comes back on or not, you
> need to use a mechanically latching relay. Those are a bit old
> fashioned and hard to find now, and tend to be low voltage low power
> devices. (They do, however, have a reputation for bomb-proof
> reliability, which is what you need here.) It complicates the design a
> little, but is still possible.
It gives me another phrase to google for, at least. Ta. And if
I can find a mechanically UN-latching relay, so much the better.
Low voltage, hmm? I had mains @5A in mind. Beggarit... :-)
--
Andrew Stephenson
Andrew Stephenson
popp...@ukonline.invalid.invalid "Adrian Tuddenham" writes:
O-kay, another phrase to google for. Leaving it up to residual
magnetism leaves me uneasy, I confess, given the chances that a
trip might be caused by a fire -- and we know fires do stuff to
magnets. (Okay, the Curie temperature of your average magnet's
a pretty high number, by which time any cables that were liable
to carry troublesome power will have melted or shorted, but I'm
viewing this from the POV of "if there's a way it can go wrong,
it will" and trying to make life difficult for those gremlins.)
(Oddly enough, I visited RS Components' website during my early
search but couldn't make much sense of what they were trying to
sell me. Must try again, maybe harder.)
Ta muchly. I'll go goggling for your and Phil's magic phrases.
--
Andrew Stephenson
Phil Taylor
<am...@deltrak.demon.co.uk> wrote:
> In article <040920081923383806%not...@all.invalid>
> not...@all.invalid "Phil Taylor" writes:
>
> > In article <122054...@deltrak.demon.co.uk>, Andrew Stephenson
> > <am...@deltrak.demon.co.uk> wrote:
> >
> > > [discussion]
>
> > I see. Well, if you need something that holds it's state after being
> > tripped out, regardless of whether the power comes back on or not, you
> > need to use a mechanically latching relay. Those are a bit old
> > fashioned and hard to find now, and tend to be low voltage low power
> > devices. (They do, however, have a reputation for bomb-proof
> > reliability, which is what you need here.) It complicates the design a
> > little, but is still possible.
>
> It gives me another phrase to google for, at least. Ta. And if
> I can find a mechanically UN-latching relay, so much the better.
>
> Low voltage, hmm? I had mains @5A in mind. Beggarit... :-)
As Adrian said, you can use the latching relay to switch a heavier
relay which in turn switches the mains power. You may need a
low-voltage power supply (usually 12 V) to operate the latching relay,
unless you can find one which runs on mains voltage.
Phil Taylor
Adrian Tuddenham
>... Leaving it up to residual
> magnetism leaves me uneasy
It's the same process as a hard drive but without the failure mechanisms
of the heads, motors and bearings. I've heard of hard drives failing
from these causes, but I've never heard of a hard drive failing because
the magnetism decided to disobey the laws of physics.
If the temperature reaches the Curie point of the relay frame, you will
have no way of detecting it electrically because the rest of the relay
will have already vanished.
Bad contacts are your worst enemy. Always mount relays so that the
contact gap is vertical, then any dirt will fall out from between the
contact surfaces.
David Kennedy
SNIP
Adrian,
Did you see the advert in u.a.c.m ? Debbie is having a clear out of
Classic OS hardware etc. I just wondered if anything was of use to you...
Adrian Tuddenham
<davidk...@nospamformethanksverymuchyoubastards.invalid> wrote:
Yes, thanks.
I have contacted her by e-mail; but the only bit I really wanted, the CD
burner, had already been spoken-for. If I didn't already have a
graphics tablet, I would have been very tempted; but I hardly ever use
the one I have.
Most of the rest would be very useful to someone setting up for the
first time in audio or visuals, but I already have a lot of similar
stuff in duplicate or triplicate.
Debbie Wilson
> Most of the rest would be very useful to someone setting up for the
> first time in audio or visuals, but I already have a lot of similar
> stuff in duplicate or triplicate.
I'm happy to say that almost everything will be finding a new home, even
our much-upgraded 7300 workhorse and its 8600 cousin, both of which,
plus tablets, are going to a family with children doing A-level Design.
Strangely enough, nobody wants the 80MB or 135MB Syquests :-)
Deb.
--
http://www.scientific-art.com
"He looked a fierce and quarrelsome cat, but claw he never would;
He only bit the ones he loved, because they tasted good." S. Greenfield
Andrew Stephenson
popp...@ukonline.invalid.invalid "Adrian Tuddenham" writes:
> Bad contacts are your worst enemy. Always mount relays so that the
> contact gap is vertical, then any dirt will fall out from between the
> contact surfaces.
Indeedy -- that was SOP in electromechanical telephone exchanges
made by the company which once paid me to attend their premises.
--
Andrew Stephenson
Adrian Tuddenham
The relay panels sold by RS to fit in their metal cabinets have
pre-punched holes for relay bases which are the wrong way around. When
I tackled them about this some years ago, they thought I was making it
up and asked where I had got the idea that the gaps should be vertical.
When I referred them to Herbert & Proctor, the telephone engineer's
'bible' of the 1920s, they thought I was having them on.
Bob Wardrope
<snip>
>
> I have contacted her by e-mail; but the only bit I really wanted, the CD
> burner, had already been spoken-for.
>
memory serves. I'll have a look later, if it's there, you're welcome to
it FF or the cost of postage[1].
Bob W
[1]If it comes to over £5
Adrian Tuddenham
> Adrian Tuddenham wrote:
> <snip>
> >
> > I have contacted her by e-mail; but the only bit I really wanted, the CD
> > burner, had already been spoken-for.
> >
> I might have a SCSI burner in one of my many storage boxes, Hitachi if
> memory serves. I'll have a look later, if it's there, you're welcome to
> it FF or the cost of postage [If it comes to over £5].
I'll happily pay postage if the model is one for which I have drivers in
my version of Toast (3.5.7)
Simon Slavin
<122046...@deltrak.demon.co.uk>:
> The device I seek is, basically, an ON/OFF switch with one set of
> changeover contacts. A manual control (lever, &c) selects either
> setting, while an electrical control (relay-type coil) lets ON be
> tripped OFF by a 230V 50Hz (mains) pulse. Contacts should handle
> 5A mains but 10A would be good. Enclosed as for mounting in (eg)
> a normally dry garage, where Questing Kiddiefingers are a hazard.
http://www.maplin.co.uk/
http://cpc.farnell.com/
To include switch, cut-out and molly guard, you'll probably need to order
at least two, probably three components.
Simon.
--
http://www.hearsay.demon.co.uk
Andrew Stephenson
slavins.delete....@hearsay.demon.co.uk
"Simon Slavin" writes:
Ta muchly. I'll get onto it later today (Sat). Maplin was one I
wondered about but they still register in my awareness as more of
a kit-and-pretty-gadgets outfit; but I am prepared to learn. The
name of Farnell I recall well from the 70s when they made a range
of well constructed power conditioners (aka PSUs).
--
Andrew Stephenson
Andrew Stephenson
they came to anything: I tried RS Components (very confusing, odd
site, but I think nothing there would serve my need), Maplins and
Farnell (they had some German kit that comes close so I left them
an email over the weekend; nothing heard back (yet?)). Ta again.
--
Andrew Stephenson