favorite diode for relay coil spikes and motor shutoff spikes?

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acan...@wwc.com

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Jun 28, 2007, 2:25:42 PM6/28/07
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whats everyones favorite diode to snub out relay coil spikes and
spikes across dc motors during turn on/off?

Richard Henry

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Jun 28, 2007, 2:27:18 PM6/28/07
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On Jun 28, 11:25 am, "acann...@wwc.com" <acann...@wwc.com> wrote:
> whats everyones favorite diode to snub out relay coil spikes and
> spikes across dc motors during turn on/off?

Depends.

colin

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Jun 28, 2007, 3:27:51 PM6/28/07
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<acan...@wwc.com> wrote in message
news:1183055142.2...@z28g2000prd.googlegroups.com...

> whats everyones favorite diode to snub out relay coil spikes and
> spikes across dc motors during turn on/off?
>

used to be 1n4004 or something like that,
as they were such common general rectifier,
not sure what the common SM type is these days.

Colin =^.^=


Don Lancaster

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Jun 28, 2007, 9:40:35 PM6/28/07
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acan...@wwc.com wrote:
> whats everyones favorite diode to snub out relay coil spikes and
> spikes across dc motors during turn on/off?
>
1N4005, of course.

But you may want to add a series resistor to shorten the dropout time.

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: d...@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

Don Klipstein

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Jul 1, 2007, 12:26:01 AM7/1/07
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In article <5ej68jF...@mid.individual.net>, Don Lancaster wrote:
>acan...@wwc.com wrote:
>> whats everyones favorite diode to snub out relay coil spikes and
>> spikes across dc motors during turn on/off?
>>
>1N4005, of course.
>
>But you may want to add a series resistor to shorten the dropout time.

I remember some time a few years ago I last bought a bunch of 1N4000
series diodes, and 1N4007 cost hardly at all more, and I had a little need
of some higher voltage ones.

As for value of the resistor to shorten dropout time: Figure how much
voltage you can comfortably handle, resistor and diode combined. In most
applications, you also have to add the power supply voltage, such as when
the application is a transistor switching a relay.
Subtract the diode voltage (.6 or .8 volt or whatever), and the power
supply voltage in the likely event this adds to what the switching
transistor or whatever has to bear. The remaining voltage is voltage drop
of the resistor, peak. Divide that by the maximum coil current
(usually the worst case steady state coil current) and that is a
resistor value - use the next available lower available value.

- Don Klipstein (d...@misty.com)

Ross Herbert

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Jul 2, 2007, 7:09:20 AM7/2/07
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Tyco app note
http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3311.pdf
http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3264.pdf
recommends a zener + diode but they do qualify the situation with
regard to NC contacts.

Another less common technique (although widely used in relay based
telco exchanges) is to use a CR unit (capacitance - resistance series
unit). This technique has the advantage of being non-polarity concious
and does not greatly affect relay release time while quenching the
tendency to erode in-line relay contacts due to arcing.

Evox Rifa app note
http://www.evox-rifa.com/cap_catalog/rc_units/gen_info_rc.pdf

American Zettler provide some broad guidelines in this document
http://www.azettler.com/pdfs/technical_notes.pdf

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