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'[EE] Break Before Make - What does it mean?'
2004\10\29@093849 by Omer YALHI

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Recently I have been seeing the "Break Before Make" term in datasheets.  It
could be that the term is being used for centruies but I recently it caught
my eye.  What does it mean?  Anybody knows?

Regards, Omer

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2004\10\29@095301 by Rob Young

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> Recently I have been seeing the "Break Before Make" term in datasheets.
> It
> could be that the term is being used for centruies but I recently it
> caught
> my eye.  What does it mean?  Anybody knows?
>
> Regards, Omer
>

Break-before-make usually refers to a switching action.  Imagine a rotary
switch.  As you rotate the shaft, instead of momentarily shorting two poles
together, a break-before-make configuration will guarantee neither pole is
connected (BREAK contact with old pole before it MAKEs contact with the
next).

The opposite is make-before-break.

These terms (break-before or make-before) apply to nearly all mechanical and
electrical multi-pole switches and I've seen it used to describe some
software where a single processor and its digital filter could select from
multiple data streams within the processor (ie pass a pointer around to
indicate the sourcing stream and dump filter history if a new source stream
is selected).

Rob Young
spam_OUTrwyoungTakeThisOuTspamieee.org
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2004\10\29@095549 by Dave VanHorn

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At 08:48 AM 10/29/2004, Omer YALHI wrote:

>Recently I have been seeing the "Break Before Make" term in datasheets.  It
>could be that the term is being used for centruies but I recently it caught
>my eye.  What does it mean?  Anybody knows?

Just what it sounds like. It's telling you that the switch common will not
connect across the terminals.

Imagine a multi-position BBM switch with common, A, B, and C terminals.
The switch would connect to A, B, and C as you rotate it.
It is guaranteed never to connect A to B, or B to C.


In a make before break switch, the common pin of the switch is always
connected to something, and for a moment, it is connected to both terminals.

Imagine a multi-position MBB switch with common, A, B, and C terminals.
The switch would connect to A, A+B, B, B+C, C as you rotate it.

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2004\10\29@100550 by olin_piclist

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Omer YALHI wrote:
> Recently I have been seeing the "Break Before Make" term in datasheets.
> It could be that the term is being used for centruies but I recently it
> caught my eye.  What does it mean?

It means that one switch will turn off (break) before the other one will
turn on (make).  This is important, for example, in an H bridge.  When
reversing polarity, you have to make sure the previous high side on leg is
completely off before enabling the low leg for that side, else you end up
shorting the supply.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\10\29@114322 by Win Wiencke

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<Omer asks>
> Recently I have been seeing the "Break Before Make" term in datasheets.

One contact disconnects before the next one connects.  There is a moment
when no connection is made between switching contacts.

Win Wiencke
Image Logic Corporation

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2004\10\29@120759 by Omer YALHI

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I thought "break before make" was like a reliability statement somehow.  I
was way off.

Thanks for the info.

Regards, Omer

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2004\10\29@132303 by Peter L. Peres

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On Fri, 29 Oct 2004, Omer YALHI wrote:

> Recently I have been seeing the "Break Before Make" term in datasheets.  It
> could be that the term is being used for centruies but I recently it caught
> my eye.  What does it mean?  Anybody knows?

It means a changeover switch or relay will be guaranteed to first open the
circuit that is presently closed and then close the new one. This is
important to avoid 'shoot through'

Peter
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2004\10\29@145434 by Jinx

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> I thought "break before make" was like a reliability statement somehow

;-))

I'm sure there are plenty of companies who's quality control aim is
to make sure the product lasts at least long enough to get in the box
and out the door

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2004\10\29@151952 by M. Adam Davis

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A reason this is important is that some sytems are damaged when
unloaded, such as transmitters and audio amplifiers.  Make before break
is used here, where one or both loads are always connected during the
transition.

The opposite, break before make, protects systems where it would be
damaging to have the two items being switched connecting to each other
momentarily.  If you have two outputs and one input (to computers and
one monitor, for instance) you need to completely disconnect one before
connecting the other as it can be bad to short the two outputs to each
other.

Make before break implies that the pole and the two selections are all
three connected for a short period of time while switching, and the pole
is /never/ disconnected from one or more contacts.  Break before make
implies that the pole and the two selections are all disconnected
(floating) for a short period of time while switching.

-Adam

>> Recently I have been seeing the "Break Before Make" term in
>> datasheets. It
>> could be that the term is being used for centruies but I recently it
>> caught
>> my eye.  What does it mean?  Anybody knows?
>>
>> Regards, Omer
>
>
____________________________________________

2004\10\29@190107 by Rich

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In multiplex configurations a switch (either mechanical or solid state)
selects the routing of the signal.  To avoid signal contention due to more
than one signal active simultaneously, the [resent signal is discontinued
(the switch breaks) before the next signal is placed on the line (The switch
makes).  If you look in the data books for analog multiplexers you will
usually find excellent timing diagrams and literal description.  Try a
search for analog multiplexers at Analog Devices, or National or others.
Digital information is also multiplexed and similar rules apply.  But there
are also make before break configurations.  Let me know if you would like
more definition.

{Original Message removed}

2004\10\29@191114 by Rich

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OMAR:

In multiplex configurations a switch (either mechanical or solid state)
selects the routing of the signal.  To avoid signal contention due to more
than one signal active simultaneously, the [resent signal is discontinued
(the switch breaks) before the next signal is placed on the line (The switch
makes).  If you look in the data books for analog multiplexers you will
usually find excellent timing diagrams and literal description.  Try a
search for analog multiplexers at Analog Devices, or National or others.
Digital information is also multiplexed and similar rules apply.  But there
are also make before break configurations.  Let me know if you would like
more definition.


----- Original Message -----
From: "Omer YALHI" <.....oyalhiKILLspamspam@spam@teksan.com.tr>
To: "'Microcontroller discussion list - Public.'" <piclistspamKILLspammit.edu>
Sent: Friday, October 29, 2004 12:17 PM
Subject: RE: [EE] Break Before Make - What does it mean?


> I thought "break before make" was like a reliability statement somehow.  I
> was way off.
>
> Thanks for the info.
>
> Regards, Omer
>
> ______________________________________________

2004\10\30@053327 by Omer YALHI

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face
I would like the thank everyone for their input.  Now I do not what it
really means.

Regards, Omer

____________________________________________

2004\10\30@062002 by Omer YALHI

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I mistyped it, what I meant was:

I would like the thank everyone for their input.  Now I do *know* what it
really means.


-----Original Message-----
From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On Behalf Of
Omer YALHI
Sent: Saturday, October 30, 2004 12:43 PM
To: 'Microcontroller discussion list - Public.'
Subject: RE: [EE] Break Before Make - What does it mean?

I would like the thank everyone for their input.  Now I do not what it
really means.

Regards, Omer

____________________________________________

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