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Thane_Bitter
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join:2005-01-20

Thane_Bitter

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Power kill switch - sort of like an EPO

Is there such a think as a switch (120/240v 20-30 amps) that is normally closed and stays in that condition until a low voltage signal or plus "trips it" off. It stays off until some one manual flips it back on. Something like a motor contactor but without the overload hardware and works in a one shot manner?
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

lutful

Premium Member

I am not quite clear but there are industrial grade AC relays with low voltage DC control. You want "NC" version for normally closed.

John Galt6
Forward, March
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join:2004-09-30
Happy Camp

John Galt6 to Thane_Bitter

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to Thane_Bitter
Yes. The circuitry is the same minus the OLs.

mackey
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join:2007-08-20

mackey to lutful

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to lutful
said by lutful:

You want "NC" version for normally closed.

While you could do it with a NC relay, it will default to "on" when powered up. If he needs it to stay off until manually powered on he wants either a 2-pole NO relay or 2 single pole NO relays (both with high voltage coils) and a 3rd SPDT relay with a low voltage coil to interface with the low voltage control (making it SPDT allows him to use either "pulse low voltage on to shut off" or "shut off low voltage to shut off high voltage").

/M

KA0OUV
Premium Member
join:2010-02-17
Jefferson City, MO

1 recommendation

KA0OUV to Thane_Bitter

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to Thane_Bitter
Shunt trip Breaker.

Thane_Bitter
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What I want is basically a power disconnect that can be remotely triggered and can't be un-triggered except by physically going over to it and resetting it.

The main contacts are closed all the time and stay in that position if the line power drops in or out (as in a power failure or other interruption). They only open if a button is pressed at a remote station and stay that way. Once it is triggered, resetting the button cannot restore the closed position of the main power contacts (otherwise it would just be a remote power switch).

I think KA0OUV idea might work, though the over protection of the breakers isn't needed.

mackey
Premium Member
join:2007-08-20

mackey

Premium Member

That would work, as would a set/reset relay controlling the coil of a standard NO relay.

/M

leibold
MVM
join:2002-07-09
Sunnyvale, CA
Netgear CG3000DCR
ZyXEL P-663HN-51

leibold to Thane_Bitter

MVM

to Thane_Bitter
The shunt-trip breaker is a great choice for this application since it is designed to disconnect an electrical load quickly and safely in an emergency. It also fulfills the criteria of allowing remote disconnect but no remote reconnect.

For the power conscious another benefit is that it does not require a continuous hold current like a relay would.

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6 to Thane_Bitter

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What are you controlling?
John Galt6

John Galt6 to Thane_Bitter

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to Thane_Bitter
»www.ebay.com/bhp/shunt-t ··· -breaker

nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO

nunya to Thane_Bitter

MVM

to Thane_Bitter
Shunt trip breaker or a contactor with a latching relay on the coil (think pump control with an on / off relay).
lawsoncl
join:2008-10-28
Spirit Lake, ID

lawsoncl to Thane_Bitter

Member

to Thane_Bitter
A shut trip breaker would fit the bill and might be simple to install in the breaker panel, but they are a little spendy new (ebay used might be within reason). They are typically used to trip a breaker when the fire alarm goes off for example.

You could also do this with a relay that latches on with a button press. Kicking it off would require cutting power to the relay coil momentarily, either by interrupting remotely or use another relay tripped remotely.

Thane_Bitter
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join:2005-01-20

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Piece (of Crap) lab equipment. It has soft button controls and on rare occasion does not respond to inputs in a timely manner as such it has to be unplugged in a hurry. The issue is the plug is right behind the machine, and very hard to get at when the machine is misbehaving.

Jack_in_VA
Premium Member
join:2007-11-26
North, VA

Jack_in_VA

Premium Member

said by Thane_Bitter:

Piece (of Crap) lab equipment. It has soft button controls and on rare occasion does not respond to inputs in a timely manner as such it has to be unplugged in a hurry. The issue is the plug is right behind the machine, and very hard to get at when the machine is misbehaving.

Why not get it repaired or replaced instead of trying to rig a Rube Goldberg relay on it?

Thane_Bitter
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Thane_Bitter

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It has been an operatic saga of repair which probably will be ending in a lawsuit, but that is another story. Suffice to say it has dragged on too long and I am unconvinced with their bandage software fixes.

mackey
Premium Member
join:2007-08-20

1 recommendation

mackey

Premium Member

My vote is still the set/reset (aka latching) relay. Here is one rated for 30A with a 12v DC coil: »www.digikey.com/product- ··· D/560939 . Just wire a remote button to the reset coil and a local button to the set coil.

/M
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

lutful

Premium Member

said by mackey:

My vote is still the set/reset (aka latching) relay. Here is one rated for 30A with a 12v DC coil: »www.digikey.com/product- ··· D/560939 . Just wire a remote button to the reset coil and a local button to the set coil.

Did not know about such relays. Very useful product to use on a PCB project that controls AC from microcontroller logic.

leibold
MVM
join:2002-07-09
Sunnyvale, CA
Netgear CG3000DCR
ZyXEL P-663HN-51

leibold to mackey

MVM

to mackey
I guess one factor that helps to decide between bi-stable or latching relay and shunt-trip breaker is whether the control voltage can come from a low voltage power supply (relay) or whether the line voltage itself should be used (shunt-trip).

When choosing a relay beware that contacts are often rated for resistive load only while the data sheet for a breaker usually also gives information about inductive loads (often in form of a horsepower rating for attached electric motors).