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LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Fri Mar 27, 2015 7:08 am Post subject: Relays

I need some help from the experts.  Digi-key has over 13,000 different 

power relays over 2 amps, and selecting one, for a novice like me, is a 

daunting task.



The relay is for the e-bus battery feed on a 14 volt system.  The load 

is currently 12 amps, but I have been challenged to better define my 

electrical design objects and possibly reduce the load down to 8 amps.  

I don't think that will change the relay selection if I were to use a 

design of 5-20 amps.



I selected TE Connectivity 1432793-1 Automotive relay SPDT 30A 12V. Here 

is the link 

<http://www.digikey.com/product-detail/en/1432793-1/PB1773-ND/1236843>



It is non latching with a diode across the coil.  Some of the specs, 

however, have me confused.

The Coil voltage is 12VDC but the Switching voltage is 14 VDC - Nom.  Is 

this an issue?

Also the Turn On Voltage (Max) is 7.8 VDC and Turn Off Voltage (Min) 1.2 

Volts.  Does this mean that the coil requires 7.8 volts to latch and it 

will un-latch if voltage drops below 1.2 volts?



I see that most of the automotive relays have high ohm resistors across 

the coil, or nothing across the coil.  When would you select a resistor, 

diode or nothing?



I have another need for a relay in my airplane.  My EFIS remote 

annunciation mute requires a contact to be close via 2 terminals via a 

momentary switch.  The vendor does not specify a current requirement for 

the switch, and when I contacted them they said any switch would work is 

is a fraction of an amp.  I would mute the EFIS with one of the buttons 

on my control stick, however my control stick only has a common ground, 

so all switches close to ground. This would not work for the remote mute.

Is there any reason why a relay wouldn't work?

Would the relay above work?  It probably is not the best choice, but it 

is only $4 and it would make for common spare parts, so if it would work 

it could be my 'best' choice.



Larry

RV-10 Builder

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

recapen(at)earthlink.net
Guest

Posted: Fri Mar 27, 2015 8:45 am Post subject: Relays

I have similar installed in my 6A.  That relay will work for both applications.  Be careful about the relay activation circuit-ground the correct side.





Sent from my Verizon Wireless 4G LTE smartphone



-------- Original message --------

From: Larry Rosen  

Date:03/27/2015  09:06  (GMT-07:00) 

To: aeroelectric-list(at)matronics.com 

Subject: AeroElectric-List: Relays 

--> AeroElectric-List message posted by: Larry Rosen <n205en(at)gmail.com>



I need some help from the experts.  Digi-key has over 13,000 different 

power relays over 2 amps, and selecting one, for a novice like me, is a 

daunting task.



The relay is for the e-bus battery feed on a 14 volt system.  The load 

is currently 12 amps, but I have been challenged to better define my 

electrical design objects and possibly reduce the load down to 8 amps.  

I don't think that will change the relay selection if I were to use a 

design of 5-20 amps.



I selected TE Connectivity 1432793-1 Automotive relay SPDT 30A 12V. Here 

is the link 

<http://www.digikey.com/product-detail/en/1432793-1/PB1773-ND/1236843>



It is non latching with a diode across the coil.  Some of the specs, 

however, have me confused.

The Coil voltage is 12VDC but the Switching voltage is 14 VDC - Nom.  Is 

this an issue?

Also the Turn On Voltage (Max) is 7.8 VDC and Turn Off Voltage (Min) 1.2 

Volts.  Does this mean that the coil requires 7.8 volts to latch and it 

will un-latch if voltage drops below 1.2 volts?



I see that most of the automotive relays have high ohm resistors across 

the coil, or nothing across the coil.  When would you select a resistor, 

diode or nothing?



I have another need for a relay in my airplane.  My EFIS remote 

annunciation mute requires a contact to be close via 2 terminals via a 

momentary switch.  The vendor does not specify a current requirement for 

the switch, and when I contacted them they said any switch would work is 

is a fraction of an amp.  I would mute the EFIS with one of the buttons 

on my control stick, however my control stick only has a common ground, 

so all switches close to ground. This would not work for the remote mute.

Is there any reason why a relay wouldn't work?

Would the relay above work?  It probably is not the best choice, but it 

is only $4 and it would make for common spare parts, so if it would work 

it could be my 'best' choice.



Larry

RV-10 Builder



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tim2542(at)sbcglobal.net
Guest

Posted: Fri Mar 27, 2015 9:15 am Post subject: Relays

And you can pick up that relay or this one:

http://www.bandc.biz/spdtsealedrelay12v40a.aspx

at any NAPA store, they're pretty common.

But there must be a better way to control the EFIS, using a relay for that function doesn't seem very elegant.  What control stick is it?

Tim



[quote] On Mar 27, 2015, at 9:44 AM, Ralph E. Capen <recapen(at)earthlink.net> wrote:

 

 I have similar installed in my 6A.  That relay will work for both applications.  Be careful about the relay activation circuit-ground the correct side

yellowduckduo(at)gmail.co
Guest

Posted: Fri Mar 27, 2015 10:08 am Post subject: Relays

Often when I see two wires like to make some electronic selection I can 

trace them back and find out that one is actually a ground.

Ken



On 27/03/2015 1:14 PM, Tim Andres wrote:

 	  Quote: 	
		   And you can pick up that relay or this one:

 http://www.bandc.biz/spdtsealedrelay12v40a.aspx

 at any NAPA store, they're pretty common.

 But there must be a better way to control the EFIS, using a relay for 

 that function doesn't seem very elegant.  What control stick is it?

 Tim



 On Mar 27, 2015, at 9:44 AM, Ralph E. Capen <recapen(at)earthlink.net 

 <mailto:recapen(at)earthlink.net>> wrote:



> I have similar installed in my 6A.  That relay will work for both 

> applications.  Be careful about the relay activation circuit-ground 

> the correct side.

> Sent from my Verizon Wireless 4G LTE smartphone

> -------- Original message --------

> From: Larry Rosen

> Date:03/27/2015 09:06 (GMT-07:00)

> To: aeroelectric-list(at)matronics.com 

> <mailto:aeroelectric-list(at)matronics.com>

> Subject: Relays

>

> 

> <n205en(at)gmail.com <mailto:n205en(at)gmail.com>>

>

> I need some help from the experts.  Digi-key has over 13,000 different

> power relays over 2 amps, and selecting one, for a novice like me, is a

> daunting task.

>

> The relay is for the e-bus battery feed on a 14 volt system. The load

> is currently 12 amps, but I have been challenged to better define my

> electrical design objects and possibly reduce the load down to 8 amps.

> I don't think that will change the relay selection if I were to use a

> design of 5-20 amps.

>

> I selected TE Connectivity 1432793-1 Automotive relay SPDT 30A 12V. Here

> is the link

> <http://www.digikey.com/product-detail/en/1432793-1/PB1773-ND/1236843>

>

> It is non latching with a diode across the coil.  Some of the specs,

> however, have me confused.

> The Coil voltage is 12VDC but the Switching voltage is 14 VDC - Nom.  Is

> this an issue?

> Also the Turn On Voltage (Max) is 7.8 VDC and Turn Off Voltage (Min) 1.2

> Volts.  Does this mean that the coil requires 7.8 volts to latch and it

> will un-latch if voltage drops below 1.2 volts?

>

> I see that most of the automotive relays have high ohm resistors across

> the coil, or nothing across the coil.  When would you select a resistor,

> diode or nothing?

>

> I have another need for a relay in my airplane.  My EFIS remote

> annunciation mute requires a contact to be close via 2 terminals via a

> momentary switch.  The vendor does not specify a current requirement for

> the switch, and when I contacted them they said any switch would work is

> is a fraction of an amp.  I would mute the EFIS with one of the buttons

> on my control stick, however my control stick only has a common ground,

> so all switches close to ground. This would not work for the remote mute.

> Is there any reason why a relay wouldn't work?

> Would the relay above work?  It probably is not the best choice, but it

> is only $4 and it would make for common spare parts, so if it would work

> it could be my 'best' choice.

>

> Larry

> RV-10 Builder

> http://forums.matronics.==========================nbsp; - List 

> Contribution 

> Wenbsp;                        &nbf="http://www.matronics.com/contribution">http://www.matronics.com/contrib=======================================

>

> kyÂ·Ã¨Å¾Ã›"ÃÃÅ“Â¢Z+Ã“M4Ã“GÃšqÃ§(ÂºÂ¸Å¾Â®wÂ°râ€¹Â«â€°ÃªÃ“â€¦Ã Â®Â%yÃ‹kâ€°Ã‚Ã¢Â²Ã‘&j)EÂ¢Â»Â¦RÃ‡Ââ€¦Ã£Â¶Âº'â€°Ã‹Å Ã‹EyÂ«nÂÃ« 

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> Å¡Â¶Âº'â€°Ã‹Â¢oÃjÃ¸ jÃš+ÃªÃ¨WÅ“Â¶Â¸Å“.+-â€ Ã›iÃ¿Ã¼0Ã‚fÂÂ®â€°Ã¢rÃ‡(â€ºÃ³ZÂ¾(Â¶Å Ã€zÂºâ€¢Ã§-Â®'Å Ã‹hÃ€DÃ£H %â€žSâ€˜PÃ„â€™jg ÂÃ¦Ârâ€°Ãz{Zâ€“ÃŠÂ½Â¨Â¥iÂ¹^Â¾&Ââ€¦Ã¥Å¾lZ+Âºkâ€ Â·Å¸â€ Ã›iÃ¿Ã·Ã¨Â®Ã©Â¬â„¢Â«kÂ¢xÅ“Â±ÃŠ&â€ Ã›iÃ¿Ã·Ã¨Â®Ã©Â¬â„¢Â«kÂ¢xÅ“Â±ÃŠ&Ã½Â¢Ã¢Â²ÃÂ¨Å¾ÃšÃ¢nÃ«bÂ¢uÅ¾m(Ây8ZÅ¾LÂ¨Â¹Ãº+ÃŠâ€¹Â«ÂÃ©ÃžÂ®â€¹Â¬Â²ÃªiÂ¢Â»LjÃ›CÂÂ©exÂ¸Â¬Â´fÅ vÂ¡ÂÃ§Ã¡Â¶ÃšÃ¿0â„¢Â«kÂ¢xÅ“Â±ÃŠ&Ã½ÃŠ'Â¶Â¸â€ºÂºÃ˜Â¨Å¾mÂ§Ã¿Ã°Ãƒ 

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 *

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edpav8r(at)yahoo.com
Guest

Posted: Fri Mar 27, 2015 1:26 pm Post subject: Relays

Larry,



Ken's comment about tracing the EFIS mute circuit is a good idea, but be careful. There are two ways this circuit could be designed: input pin internally pulled up or internally pulled down.  One method (input pulled up) *should* allow you to use your grip switch directly (assuming the EFIS doesn't use an isolated power supply, which is unlikely), but the other method (input pulled down) requires a relay or switch that's isolated from ship's ground.



I would contact the EFIS manufacturer again and ask specifically if externally grounding one of the pins will work to activate the mute circuit.  If so, problem solved -- wire the appropriate pin directly to your grip switch.



If not, and you do need a relay, I can offer this option:



I have a few of these relays...



http://bit.ly/1Nj9UEt



..that were excess from a past project.  I'd be happy to put one on a piece of perforated prototype board with a diode and some Tefzel wire leads (labeled!) and mail it to you.  If you want it, just email me your address off the forum and I'll get it out to you ASAP.



Cheers,



Eric

 	  Quote: 	
		   On Mar 27, 2015, at 8:06 AM, Larry Rosen <n205en(at)gmail.com> wrote:

 

 

 

 I need some help from the experts.  Digi-key has over 13,000 different power relays over 2 amps, and selecting one, for a novice like me, is a daunting task.

 

 The relay is for the e-bus battery feed on a 14 volt system.  The load is currently 12 amps, but I have been challenged to better define my electrical design objects and possibly reduce the load down to 8 amps.  I don't think that will change the relay selection if I were to use a design of 5-20 amps.

 

 I selected TE Connectivity 1432793-1 Automotive relay SPDT 30A 12V. Here is the link <http://www.digikey.com/product-detail/en/1432793-1/PB1773-ND/1236843>

 

 It is non latching with a diode across the coil.  Some of the specs, however, have me confused.

 The Coil voltage is 12VDC but the Switching voltage is 14 VDC - Nom.  Is this an issue?

 Also the Turn On Voltage (Max) is 7.8 VDC and Turn Off Voltage (Min) 1.2 Volts.  Does this mean that the coil requires 7.8 volts to latch and it will un-latch if voltage drops below 1.2 volts?

 

 I see that most of the automotive relays have high ohm resistors across the coil, or nothing across the coil.  When would you select a resistor, diode or nothing?

 

 I have another need for a relay in my airplane.  My EFIS remote annunciation mute requires a contact to be close via 2 terminals via a momentary switch.  The vendor does not specify a current requirement for the switch, and when I contacted them they said any switch would work is is a fraction of an amp.  I would mute the EFIS with one of the buttons on my control stick, however my control stick only has a common ground, so all switches close to ground. This would not work for the remote mute.

 Is there any reason why a relay wouldn't work?

 Would the relay above work?  It probably is not the best choice, but it is only $4 and it would make for common spare parts, so if it would work it could be my 'best' choice.

 

 Larry

 RV-10 Builder

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Fri Mar 27, 2015 2:04 pm Post subject: Relays

 	  Quote: 	
		   But there must be a better way to control the EFIS, using a relay for 

 that function doesn't seem very elegant.  What control stick is it?

 Tim



I confirmed with the company and switching to ground is not what they want.
	


The control sticks are Tosten CS-8 

<http://tostenmanufacturing.com/product/cs-8-aircraft-grip/> I really 

like the way the feel and I bought them when I was more electrically 

naive.  My purchase decision may have been different if I knew then what 

I know now.  Thank you aeroelectric.  I am not sure how I am going to 

wire the PTT since the PS Engineering audio panel wants the Mic PTT and 

Mic Lo switched.  Not sure if there is an alternate method or if I need 

yet another relay.



Larry

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Fri Mar 27, 2015 7:14 pm Post subject: Relays

Larry;



Although you have received some anecdotal responses to your relay question

I'll try to directly answer each of your specific questions.



1: The 30 amp relay you have chosen will safely switch loads from a fraction

of an amp up to its 30 Amp rating, so you are correct in the assumption

that, within reason, your endurance buss load is immaterial to relay choice.



2: A 12V automotive relay is designed to function in the

automotive/vehicular world, therefore any voltage from 9-10 up to 15-16 will

be happily accommodated. Your 14V is not an issue, this is "standard"

vehicular voltage. If you look at the spec sheet for the relay you've chosen

the contacts are rated for 16 volts by the manufacturer.



3: Turn on voltage (max) 7.8 means that if you were to slowly increase the

voltage across the coil from zero that by the time it reached 7.8 the

contacts would have transferred to the on condition. (not latched as you

have stated, this is NOT a latching relay) They might transfer at some value

below 7.8, but will have transferred for sure by 7.8.



4: Turn off voltage (min) 1.2 means that if you were to slowly decrease the

voltage across the coil from the rated 12 volts down to zero, the contacts

would have transferred to the off state by the time the voltage reached 1.2

volts. They might switch off at some level above 1.2 but for sure they will

be off by the time you reach 1.2. (your interpretation of turn on/turn off

voltages is correct, but again this relay does not unlatch by 1.2 volts as

it is not a latching relay. The contacts simply transfer back to the "at

rest" position)



5: I don't see where you found relays with resistors across the coils. They

do exist, but the coil resistance numbers in the Digikey relay tables refer

to the resistance of the coil itself. It is only meaningful with respect to

the amount of current drawn by the coil when energized and if you are using

a 12 volt relay in a 12 volt system it's not something you generally need

worry about. Components added across relay coils such as resistors and

diodes are introduced in an effort to reduce the inductive effects of

turning off the coil. The action of turning off an inductive load (the relay

coil) imposes momentary high voltages (inductive spikes) across the switch

contacts which control the coil causing arcing and possibly reducing the

life of the switch contacts. A resistor provides an alternative path for the

inductive current to dissipate and a diode effectively "shorts" the

inductive current. There are many arguments for each of the methods of

reducing this effect with some advocating diodes as being the most cost

effective solution while others maintain that the slightly increased

switching time caused by the diode is detrimental. Others advocate MOVs,

resistors, or bi-directional zeners, while some suggest nothing is required.

The simple diode installed by some manufacturers, such as the one you've

chosen, seems to be the most widely accepted cost effective method of

mitigating this effect.



6: This relay would "probably" work for your EFIS issue BUT you might

possibly need gold contacts for that application if the current being

switched is low enough. For extremely low currents there is insufficient

arcing to keep silver/tin oxide contacts clean and the oxidation which forms

on them will insulate against very low currents, hence the need for gold

contacts in signal level circuits. ( and no you can't use the gold contacts

for high currents as the arcing will destroy the ultra thin gold plating.)



Hope this somewhat solidifies your understanding of the terminology you've

questioned.



Bob McC

[quote] --

_________________
Bob McC
Falco #908
(just starting)

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Fri Mar 27, 2015 8:31 pm Post subject: Relays

Bob McC,

Thanks, very helpful.  It did help solidify my understanding.



Would you help me identify a relay that would be a better choice, or 

point me into the right direction.  It doesen't look like the automotive 

type relays have gold contacts they are designed for high (10A and 

above) loads.

Larry



On 3/27/2015 11:13 PM, Bob McCallum wrote:

[quote]

 6: This relay would "probably" work for your EFIS issue BUT you might

 possibly need gold contacts for that application if the current being

 switched is low enough. For extremely low currents there is insufficient

 arcing to keep silver/tin oxide contacts clean and the oxidation which forms

 on them will insulate against very low currents, hence the need for gold

 contacts in signal level circuits. ( and no you can't use the gold contacts

 for high currents as the arcing will destroy the ultra thin gold plating.)



 Hope this somewhat solidifies your understanding of the terminology you've

 questioned.



 Bob McC

> --

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Mar 28, 2015 12:12 pm Post subject: Relays

OOPS!  I didn't get all the downloads on the thread . . .

 You've had some excellent feedback already . . .



 The only thing I would add is to not obsess over

 contact ratings. If you pull the engineering data

 sheets on any of the Digikey offerings, you'll find

 that each product's ratings are accompanied with

 a service life figure in the tens of thousands of

 cycles.



 Given that you'll probably fly your airplane no

 more than 100 hours/year . . . how many years or

 hours of flight are required to impress say 5000

 cycles on any of your switches/relays?



 Bottom line is that I've replaced far more such devices

 that suffered from environmental effects of age and

 DISUSE than for failure to observe the manufacturer's

 published ratings.



 

 The relay is for the e-bus battery feed on a 14 volt system.  The load is currently 12 amps, but I have been challenged to better define my electrical design objects and possibly reduce the load down to 8 amps.  

 I don't think that will change the relay selection if I were to use a design of 5-20 amps.



 Use anything you can find that is in-expensive and

 easy to replace. Suggest you install something like

 this.



  http://tinyurl.com/qagvybn



 I've purchased similar devices for as little as

 $2.00 each in hundreds. Given that this is the

 ALTERNATE feed path relay, it will get cycled ONCE

 per flight so maybe a couple hundred times per year.

 Further, its functionality is PREFLIGHT tested thus

 limiting its ability to become an undetected latent

 failure.



 I selected TE Connectivity 1432793-1 Automotive relay SPDT 30A 12V. Here is the link < http://www.digikey.com/product-detail/en/1432793-1/PB1773-ND/1236843 >



 It is non latching with a diode across the coil.  Some of the specs, however, have me confused.

 The Coil voltage is 12VDC but the Switching voltage is 14 VDC - Nom.  Is this an issue?

 Also the Turn On Voltage (Max) is 7.8 VDC and Turn Off Voltage (Min) 1.2 Volts.  Does this mean that the coil requires 7.8 volts to latch and it will un-latch if voltage drops below 1.2 volts?



   Pretty much. 



 I see that most of the automotive relays have high ohm resistors across the coil, or nothing across the coil.  When would you select a resistor, diode or nothing?



   Either resistor or diode is fine . . . I prefer

   the diode but again . . . for a few hundred

   cycles per YEAR . . . the precise suppression

   method is exceedingly un-critical.



 

 I have another need for a relay in my airplane.  My EFIS remote annunciation mute requires a contact to be close via 2 terminals via a momentary switch.  The vendor does not specify a current requirement for the switch, and when I contacted them they said any switch would work is is a fraction of an amp.  I would mute the EFIS with one of the buttons on my control stick, however my control stick only has a common ground, so all switches close to ground. This would not work for the remote mute.



 

 Is there any reason why a relay wouldn't work?

 Would the relay above work?  It probably is not the best choice, but it is only $4 and it would make for common spare parts, so if it would work it could be my 'best' choice.



   This is not a flight-critical functionality. If

   I were spec'ing the relay into a TC aircraft,

   I would pick something with established reliability

   (just to keep the paper shufflers happy). For our

   purposes, any "telecom" rated (low current contacts)

   like this would do just fine.



  http://www.digikey.com/product-detail/en/1461070-5/1461070-5-ND/1427501

 

 

  The logistical problem with these relays is how

  to bolt he little buggers to an airplane. Unlike

  the one I cited above, these critters are designed

  to solder to an etched circuit board and don't feature

  mounting ears of any type.



  Probably the easiest thing to do is solder 22AWG

  lead wires to the proper 4 pins . . . perhaps install

  a coil-suppression diode right on the pins. Pot the

  assembly into a 'bolt-able' housing with long-set

  epoxy with the wires hanging out. Alternatively,

  mount to a perf-board and bring vibration supported

  wires off the board. There's no graceful way to do

  this. From a production perspective, I've often

  considered offering a relay something like this



 [img]cid:.0[/img]



 

  http://www.digikey.com/product-detail/en/TQ2SL-12V/255-2853-ND/649407 



 



 

  mounted within one of our stock d-sub housings sorta

  like this . . .

 [img]cid:.1[/img]



  This is one way to incorporate such relays in

  a manner that looks more business-like for airplanes.

  Also much less prone to failure by reason

  of installation shortfall . . .



  It IS a bit of a conundrum . . . but know that ratings for

  these relays are the least of the issues.



 



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 29, 2015 12:12 pm Post subject: Relays

Here's some additional materials that go toward

understanding 'contact science' . . . whether

you're talking about switches or relays. Relays

are just remotely operated switches. The

CONTACTS share the same physics.



http://tinyurl.com/nda9su5



Here's a couple of documents produced by one of the

'granddaddies' of switch and relay business



http://tinyurl.com/ngnjglx



http://tinyurl.com/nenvxrx



   Bob . . .



   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Sun Mar 29, 2015 6:13 pm Post subject: Re: Relays

Quote from the Tyco paper,  	  Quote: 	
		  Some relay users connect a diode across the inductive load to prevent counter-voltage from reaching the contacts. . . . While this is an acceptable method of protecting the contacts, it does result in lengthened hold-up time of the inductive load. 	


So Bob, this does not contradict the results of your lab experiments (If I remember your posts correctly.) that demonstrate that arc suppression diodes delay opening of relay contacts, but do not cause the contacts to open slower once they start opening.  A hold-up delay of less than one second is of no consequence in most amateur built aircraft.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 29, 2015 7:06 pm Post subject: Relays

At 21:13 2015-03-29, you wrote:

 	  Quote: 	
		  



Quote from the Tyco paper,

 > Some relay users connect a diode across the inductive load to 

 prevent counter-voltage from reaching the contacts. . . . While 

 this is an acceptable method of protecting the contacts, it does 

 result in lengthened hold-up time of the inductive load.



So Bob, this does not contradict the results of your lab experiments 

(If I remember your posts correctly.) that demonstrate that arc 

suppression diodes delay opening of relay contacts, but do not cause 

the contacts to open slower once they start opening.  A hold-up 

delay of less than one second is of no consequence in most amateur 

built aircraft.


	




   Good eye!!!! There was a lengthy discussion here

   on the list some years ago. About that same time,

   I was deeply immersed in some failure studies of

   relays on the roll trim system on the Beechjet.

   Even the folks who supplied the relays couldn't

   figure out what was going on . . . and it took

   me several years of sifting the reports and doing

   the science to identify and demonstrate

   the root cause.



   Here's 'the meat' of a report I crafted for RAC.



http://tinyurl.com/pstsggm



   Turns out that primary stresser for causing very

   lightly loaded contacts to stick was an effect not

   discussed or warned against in any relay applications

   document I could find.



   Some years earlier, I was able to explore and confirm

   that the form of coil suppression on a relay had

   very little effect on the contact spreading velocity

   once  the relay started to open. Diodes have

   a PROFOUND effect on drop out delay . . . but that

   forcing function has almost no effect on spreading

   velocity . . . hence tendency to arc. Once the armature

   comes off the electro-magnet pole-piece, the AIR GAP

   produced therein weakens the magnetic force far

   more rapidly than the diode can retard it's decay.



http://tinyurl.com/qgkgo88



   It's tar-bucket stepped into by many

   authors in the 'relay arts'. A document

   from Tyco was often cited here on the list where

   one ASSUMED that because the diode retards

   drop-out response . . . if just logically followed

   that the contacts must spread more slowly as well.



http://tinyurl.com/ndc6cvl



   Now, if we were using relays in systems wire TIMING

   was critical . . . the extended drop-out delay

   might cause other problems . . . but not reduced

   contact life due to aggravated arcing.

   Bob . . .

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Mon Mar 30, 2015 4:39 am Post subject: Relays

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Mon Mar 30, 2015 5:38 am Post subject: Re: Relays

Relays can also stick for mechanical reasons unrelated to contact current or to coil current.  Many relays are made with a thin film of non-magnetic material between the coil core and the armature to prevent them from sticking together due to residual magnetism.  If that thin film is missing or damaged, the relay can stick closed.

  At work a machine operator complained that the equipment started up all by itself.  The equipment was a large mixing tank powered by a 5 HP three phase motor.  The operator pushed the stop button and the run-light went out.  Later the operator noticed that the mixer was running again.  He called an electrician who confirmed that the motor started running all by itself.  (Even reliable witnesses make mistakes.)  I got involved and found that the start-stop buttons send signals to a PLC (Programmable Logic Controller).  And the PLC controls the run indicator light and an AC contactor.  The PLC worked fine.  When the stop button was pushed, the run indicator light went out and the PLC opened the contactor coil circuit.  But the contactor did not open.  So it turns out that the motor did not start up all by itself.  It never stopped running when the stop button was pushed.  I replaced the contactor and that fixed the problem.  I examined the bad contractor on the workbench but could not find any mechanical problem with it.  My conclusion was that the contactor was sticking closed due to either residual magnetism or due to atmospheric pressure (like when two oily flat surfaces can be hard to separate).  The contactor did have two large mating surfaces that fit perfectly together.  The moral of the story is, expect the unexpected and verify what others tell you.

_________________
Joe Gores

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Mon Mar 30, 2015 2:25 pm Post subject: Relays

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Mon Mar 30, 2015 7:28 pm Post subject: Re: Relays

I will try one more time.  Not sure why my message got through without any text.



Putting the signal relay into a backshell seems like an interesting project I would like to try.

Are there any d-sub backshells that are better suited to stuffing the relay into?

I have looked some electrical catalogs for a mounting bracket like you describe.  I take it it is a roll your own.

And finally would you solder wire to the relay and use pins into the d-sub?



I will post pictures when I get it done.

Larry

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

raymondj(at)frontiernet.n
Guest

Posted: Tue Mar 31, 2015 4:56 am Post subject: Relays

Larry,



FWIW, I have had the same problem in the past, and found it was 

associated with sending or replying to emails with images 

embedded/attached to them.  Didn't spend the time to find a solution 

other than to avoid images, so I can't offer any real solution to the 

problem.



do not archive



Raymond Julian

Kettle River, MN



The things we admire in men, kindness and generosity, openness, honesty, 

understanding and feeling are the concomitants of failure in our system. 

And those traits we detest, sharpness, greed, acquisitiveness, meanness, 

egotism and self-interest are the traits of success. And while men 

admire the quality of the first they love the produce of the second. 

-John Steinbeck, novelist, Nobel laureate (1902-1968)



On 03/30/2015 10:28 PM, LarryRosen wrote:

 	  Quote: 	
		   



 I will try one more time.  Not sure why my message got through without any text.



 Putting the signal relay into a backshell seems like an interesting project I would like to try.

 Are there any d-sub backshells that are better suited to stuffing the relay into?

 I have looked some electrical catalogs for a mounting bracket like you describe.  I take it it is a roll your own.

 And finally would you solder wire to the relay and use pins into the d-sub?



 I will post pictures when I get it done.

 Larry



 --------

 Larry Rosen

 #40356

 N205EN (reserved)

 &lt;http&gt;





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=440053#440053

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 31, 2015 11:40 am Post subject: Relays

At 22:28 2015-03-30, you wrote:

 --> AeroElectric-List message posted by: "LarryRosen" <N205EN(at)gmail.com>



 I will try one more time.  Not sure why my message got through without any text.



 Putting the signal relay into a backshell seems like an interesting project I would like to try.



 Are there any d-sub backshells that are better suited to stuffing the relay into?

 I have looked some electrical catalogs for a mounting bracket like you describe.

 I take it it is a roll your own. And finally would you solder wire to the relay

 and use pins into the d-sub?



   Good for you . . .



   The legacy DSub shells have internal dimensions

   that closely mimic connectors themselves. The D15

   backshells I use have internal 'thickness' heights

   on the order of 0.45"



   The relay you choose must have at least one dimension

   equal to or less than the internal height of the shell.

   If you like, I can mail you a shell and bracket. The

   connectors and hardware are prolific.



   Relays too. . . there's probalby 100 parts

   in the Digikey catalog suited you task. First

   crack at a search



 [img]cid:.0[/img]

   http://tinyurl.com/p3f3cbh



  A surface mount version is good . . . you might

  have to cut pins off anyhow. Neat doesn't count

  Use solder cup connector and 24 or 26 awg wire.

  Solid wire is okay . . . after you've check it

  for functionality, you'll pot it with hot-glue.



  Let me know if you want the parts.

 

   Bob . . .

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