Relay back emf protection

[Gareth Magennis]

Following on from the Automotive Relay thread;

What are the reasons behind the apparent fact that relays last longest in
this order of coil protection:

1. No protection at all
2. Zener diode
3. Resistor (6 x coil resistance)
4. Diode


(No protection being the relay lasts longest, the standard diode being the
worst thing for the relay - forget the circuit protection issues just now)


From this data - scroll to the bottom for a chart:

http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=Automotive_Relay_Applications&DocType=CS&DocLang=EN



Cheers,


Gareth.

 

[amdx]

On 10/22/2014 1:52 PM, Gareth Magennis wrote:

Following on from the Automotive Relay thread;

What are the reasons behind the apparent fact that relays last longest
in this order of coil protection:

Arcing on opening.



> 1. No protection at all

Fastest opening. Less damage to contacts.

> 2. Zener diode

If indeed your order is correct,
Slow opening.

> 3. Resistor (6 x coil resistance)

Slower Opening.

> 4. Diode

Slowest Opening.
Most damage to contacts.

(No protection being the relay lasts longest, the standard diode being
the worst thing for the relay - forget the circuit protection issues
just now)


From this data - scroll to the bottom for a chart:

http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=Automotive_Relay_Applications&DocType=CS&DocLang=EN




Cheers,


Gareth.

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[bud--]

On 10/22/2014 3:23 PM, amdx wrote:

On 10/22/2014 1:52 PM, Gareth Magennis wrote:
Following on from the Automotive Relay thread;



What are the reasons behind the apparent fact that relays last longest
in this order of coil protection:


Arcing on opening.



1. No protection at all

Fastest opening. Less damage to contacts.

2. Zener diode

If indeed your order is correct,
Slow opening.

3. Resistor (6 x coil resistance)

Slower Opening.

4. Diode

Slowest Opening.
Most damage to contacts.

http://web.archive.org/web/20110104003731/http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3264.pdf

 

[John Robertson]

On 10/23/2014, 12:53 PM, bud-- wrote:

On 10/22/2014 3:23 PM, amdx wrote:
On 10/22/2014 1:52 PM, Gareth Magennis wrote:
Following on from the Automotive Relay thread;



What are the reasons behind the apparent fact that relays last longest
in this order of coil protection:


Arcing on opening.



1. No protection at all

Fastest opening. Less damage to contacts.

2. Zener diode

If indeed your order is correct,
Slow opening.

3. Resistor (6 x coil resistance)

Slower Opening.

4. Diode

Slowest Opening.
Most damage to contacts.


http://web.archive.org/web/20110104003731/http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3264.pdf

This is very interesting, it raises points I had never considered such
as the momentary current flow through the diode and coil, and how that
can stress other parts. The two articles are good reading!

It explains why (in my field of pinball repair) manufacturers stopped
putting suppression diodes on the coils and instead put them in place to
protect the driver devices (transistors/Mosfets, etc.).

Thanks for bringing this topic up!

Do note that both articles say you HAVE to protect the driver device
from the back EMF!!

John :-#)#

--
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Gareth Magennis]

"bud--" wrote in message
news:54494ed0$0$44150$c3e8da3$3a1a2348@news.astraweb.com...

On 10/22/2014 3:23 PM, amdx wrote:

On 10/22/2014 1:52 PM, Gareth Magennis wrote:
Following on from the Automotive Relay thread;



What are the reasons behind the apparent fact that relays last longest
in this order of coil protection:


Arcing on opening.



1. No protection at all

Fastest opening. Less damage to contacts.

2. Zener diode

If indeed your order is correct,
Slow opening.

3. Resistor (6 x coil resistance)

Slower Opening.

4. Diode

Slowest Opening.
Most damage to contacts.

http://web.archive.org/web/20110104003731/http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3264.pdf






Thanks for that link. Interesting indeed.


Gareth.