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rv6a(at)rogers.com
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 Posted: Mon Apr 02, 2018 3:11 pm Post subject: Warm Toggle Switch |
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Hello
My RV6A has been flying for a little over nine years. On a recent flight I noticed that the strobe toggle switch behind the panel was warm . I have an Aeroflash Nav/Strobe light combination with independent power packs for each strobe. The power packs, according to the product documentation, draw 2.7 amps each. My toggle switch is a S700-1-3. The toggle switch is a S700-1-3 and the circuit is protected by a 7.5 amp fuse. The fuse has never blown. The Nav lights are switched/fused separately
I have pulled the strobe fuse until I get this sorted out. I am wondering if this is too much current draw for this particular switch and that I should incorporate a relay into the circuit. Perhaps the switch has reached its end of service.
Thoughts?
John C
RV6A
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yellowduckduo(at)gmail.co
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| Posted: Mon Apr 02, 2018 3:30 pm Post subject: Warm Toggle Switch |
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There is history in the archives on this happening when the rivets
attaching the terminal lugs onto the switch are not tight enough.
Yes it's time for a new switch.
Ken
On 02/04/2018 7:11 PM, John wrote:
| Quote: |
Hello
My RV6A has been flying for a little over nine years. On a recent flight I noticed that the strobe toggle switch behind the panel was warm . I have an Aeroflash Nav/Strobe light combination with independent power packs for each strobe. The power packs, according to the product documentation, draw 2.7 amps each. My toggle switch is a S700-1-3. The toggle switch is a S700-1-3 and the circuit is protected by a 7.5 amp fuse. The fuse has never blown. The Nav lights are switched/fused separately
I have pulled the strobe fuse until I get this sorted out. I am wondering if this is too much current draw for this particular switch and that I should incorporate a relay into the circuit. Perhaps the switch has reached its end of service.
Thoughts?
John C
RV6A
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Mon Apr 02, 2018 5:40 pm Post subject: Warm Toggle Switch |
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John:
Yes, the switch may be the problem. Your switch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps.
They are average type switches, they are not hermetically sealed, the contacts are not silver plated. There could very easily be corrosion on the contacts and that raises the resistance of the circuit. The higher resistance can very easily cause HEAT at that contact point AND you are FEELING IT!
Find a better quality switch. I like taking a DPST (Double Pole Single Throw) Switch and wiring BOTH Sides together so it functions as a SPST (Single Throw Single Throw) Switch. So, in your case you would have a total AC Rating of 30 Amps which would be able to handle either 19 Amps or 21 Amps DC. AND the physical properties of the switch would be much more robust that that S700-1-3 switch.
BUT! DON'T STOP THERE! Other things in the circuit can be causing higher current draw.
1 - Sales brochures generally BOAST better ratings that that actually exist. The Strobe may very well be drawing higher than advertised.  Â
2 - Check the connections of the switch. If they are SCREW Terminals use star lock washers. If they are FAST-ON terminals, how easy do they slide on/off? Squeeze them with needle nose pliers so they are Very Snug.
3 - How are other connections in the circuit? Â
4 - You mentioned FUSE, check the fuse holder for any signs of corrosion. Clean it with Scotch-Brite and Contact Cleaner.
Resistance is resistance no matter where it is and that causes an increase in current draw.
Barry
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paul(at)eckenroth.com
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| Posted: Mon Apr 02, 2018 7:04 pm Post subject: Warm Toggle Switch |
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I believe this is my first attempt at actually giving advice on this list but here goes. I had the same problem with the strobe switch in my RV9 except the switch was not warm but hot. I removed the switch and soldered the rivets. Replaced the switch and the heat was gone and has been for over 700 hours. I also removed the rest of the toggle switches and gave them the same treatment. I check the switches periodically and they are always ambient temperature. I’m sure I read about soldering the rivets on this list years ago so this is not my idea.Â
Paul
On Monday, April 2, 2018, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
| Quote: | John:
Yes, the switch may be the problem. Your switch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps.
They are average type switches, they are not hermetically sealed, the contacts are not silver plated. There could very easily be corrosion on the contacts and that raises the resistance of the circuit. The higher resistance can very easily cause HEAT at that contact point AND you are FEELING IT!
Find a better quality switch. I like taking a DPST (Double Pole Single Throw) Switch and wiring BOTH Sides together so it functions as a SPST (Single Throw Single Throw) Switch. So, in your case you would have a total AC Rating of 30 Amps which would be able to handle either 19 Amps or 21 Amps DC. AND the physical properties of the switch would be much more robust that that S700-1-3 switch.
BUT! DON'T STOP THERE! Other things in the circuit can be causing higher current draw.
1 - Sales brochures generally BOAST better ratings that that actually exist. The Strobe may very well be drawing higher than advertised.  Â
2 - Check the connections of the switch. If they are SCREW Terminals use star lock washers. If they are FAST-ON terminals, how easy do they slide on/off? Squeeze them with needle nose pliers so they are Very Snug.
3 - How are other connections in the circuit? Â
4 - You mentioned FUSE, check the fuse holder for any signs of corrosion. Clean it with Scotch-Brite and Contact Cleaner.
Resistance is resistance no matter where it is and that causes an increase in current draw.
Barry
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ceengland7(at)gmail.com
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| Posted: Tue Apr 03, 2018 5:51 am Post subject: Warm Toggle Switch |
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Care to show us how you arrive at that last statement, using Ohm's Law?
On 4/2/2018 8:39 PM, FLYaDIVE wrote:
| Quote: | John:
Yes, the switch may be the problem. Your switch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps.
They are average type switches, they are not hermetically sealed, the contacts are not silver plated. There could very easily be corrosion on the contacts and that raises the resistance of the circuit. The higher resistance can very easily cause HEAT at that contact point AND you are FEELING IT!
Find a better quality switch. I like taking a DPST (Double Pole Single Throw) Switch and wiring BOTH Sides together so it functions as a SPST (Single Throw Single Throw) Switch. So, in your case you would have a total AC Rating of 30 Amps which would be able to handle either 19 Amps or 21 Amps DC. AND the physical properties of the switch would be much more robust that that S700-1-3 switch.
BUT! DON'T STOP THERE! Other things in the circuit can be causing higher current draw.
1 - Sales brochures generally BOAST better ratings that that actually exist. The Strobe may very well be drawing higher than advertised.  Â
2 - Check the connections of the switch. If they are SCREW Terminals use star lock washers. If they are FAST-ON terminals, how easy do they slide on/off? Squeeze them with needle nose pliers so they are Very Snug.
3 - How are other connections in the circuit? Â
4 - You mentioned FUSE, check the fuse holder for any signs of corrosion. Clean it with Scotch-Brite and Contact Cleaner.
Resistance is resistance no matter where it is and that causes an increase in current draw.
Barry
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rv6a(at)rogers.com
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| Posted: Tue Apr 03, 2018 5:57 am Post subject: Warm Toggle Switch |
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Ken, Barry and Paul
Thanks for your responses and excellent advice.
Much appreciated.
John C
Rv6A
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nuckolls.bob(at)aeroelect
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| Posted: Tue Apr 03, 2018 7:25 am Post subject: Warm Toggle Switch |
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At 08:39 PM 4/2/2018, you wrote:
| Quote: | John:
Yes, the switch may be the problem. Your switch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps. |
Not so.
An ampere is equal to flow of 1 Coulomb per second of electrons
past a point in the conductor. The electrons don't know if they're
AC, DC or some combination of the two. 1 amp flowing with a force
of 1 volt for 1 second represents 1 Joule of energy . . . and again,
this packet of energy knows not from which system it was generated.
This particular problem with the Carling switches has a history.
Graybeards on the List will recall a builder's repeated loss
of the switch that controlled his strobes. Something relaively
new in the Carling switches saga given that this same style of
switch had been in service on single engine Cessnas since the
middle 60's.
If you consider the physics for conducting Coulombs of electrons
to the strobes, we can count 10 metallic joints in the
switch's power path. NONE of those joints can have a resistance
of ZERO . . . it's ideally small but cannot be zero.
Four of those joints (1, 2, 9, 10_ are directly acted upon by the
installer. Two more (3,  can be influenced by the installer's
action when pressing the fast-on terminals into place. Those
same two joints can be adversely affected by operational
vibrations of wire bundles too tightly installed to the
back of switches (short or no service loops in wires).
All of said joints can be adversely influenced by
environmental effects and/or manufacturing variations.
Suffice it to say, any switch that is noticeably
warm after some time in the ON condition is probably
suffering a rise in resistance in on or more of the
10 joints illustrated.
A change in strobe system design architecture precipitated
the exchange we had about 10 years ago. You can go to
the AeroElectric List search feature on
http://www.matronics.com/forums/search.php
and search on Carling+failure+strobe+rivet
This was about the time when strobe systems were
migrating from the legacy Royer oscillator, high
voltage power supplies to the high efficiency,
high frequency constant-power supplies. Unlike
older strobes that drew LESS than normal running
current at low bus voltage, these systems were
designed to maintain strobe output at a wide range
of bus voltages, hence current draw went UP as
bus voltage goes down.
Operating strobes on the ground at idle and taxi
rpms placed extra stress on the switch.
Here'a a narrative that goes to a particular
kind of failure in the Carling swtiches:
https://goo.gl/oiZjeG
I've done teardowns on about a half dozen
switch failures with locus of the failure
was seldom repeated.
Here'a a general article on switch rating
as it relates to our use of them in airplanes.
https://goo.gl/CPtPYJ
Yes, the Carling products are inexpensive
but as Cessna and others have demonstrated for
decades, this does NOT make them unsuited to
our tasks. The laws of physics that govern
their failures are inviolate . . . meaning that
there are deducible reasons for every failure
or rash of failures.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Apr 03, 2018 7:45 am Post subject: Warm Toggle Switch |
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At 10:03 PM 4/2/2018, you wrote:
| Quote: | I believe this is my first attempt at actually giving advice on this list but here goes. I had the same problem with the strobe switch in my RV9 except the switch was not warm but hot. I removed the switch and soldered the rivets. Replaced the switch and the heat was gone and has been for over 700 hours. I also removed the rest of the toggle switches and gave them the same treatment. I check the switches periodically and they are always ambient temperature. I’m sure I read about soldering the rivets on this list years ago so this is not my idea.Â
Paul |
Good move . . . but not necessarily useful for
all switches. Barons and Bonanzas suffered a rash
of switch/breaker failures wherein a flexible braid
of fine wires intended to carry controlled
current around the pivot point to the front frame
of the switch.
This forced current to flow through the
spring. The 30A Prop Anti-Ice breaker
switch was observed to emit streams of
smoke past the toggle as the spring turned
into a heater.
[img]cid:.0[/img]
This single case prompted a kerfuffle suggesting
that ALL the switches be replaced when in fact, the
prop deice was the only high current situation that
would smoke the spring.
Similarly, the Carling switches as-received are
just fine for the purposes to which we might use
them while keeping an eye on the switch controlling
high energy strobes. It would probably be good
practice not to run such strobes on the ground.
Bob . . .
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ChasB(at)satx.rr.com
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| Posted: Wed Apr 04, 2018 6:21 am Post subject: Warm Toggle Switch |
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I went through several warm, hot, and/or shorted switches that operated my strobes. Tried several brands of switches all with the same results. Finally trouble shot the whole system and found a bad connector crimp on the positive wire that connected at the strobe power pack. Repaired same, and haven’t had a switch problem since.
Charlie
RV-6A, N11CB
San Antonio
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rv6a(at)rogers.com
Guest
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| Posted: Wed Apr 04, 2018 7:44 am Post subject: Warm Toggle Switch |
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Thanks Charlie.
John C
RV6A
| Quote: | On Apr 4, 2018, at 10:21 AM, Charles Brame <ChasB(at)satx.rr.com> wrote:
I went through several warm, hot, and/or shorted switches that operated my strobes. Tried several brands of switches all with the same results. Finally trouble shot the whole system and found a bad connector crimp on the positive wire that connected at the strobe power pack. Repaired same, and haven’t had a switch problem since.
Charlie
RV-6A, N11CB
San Antonio
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Apr 04, 2018 7:45 am Post subject: Warm Toggle Switch |
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At 09:21 AM 4/4/2018, you wrote:
| Quote: | | I went through several warm, hot, and/or shorted switches that operated my strobes. Tried several brands of switches all with the same results. Finally trouble shot the whole system and found a bad connector crimp on the positive wire that connected at the strobe power pack. Repaired same, and haven’t had a switch problem since. |
What were your observations for condition of
the materials at the failure . . . and do
you recall whether the failure was related
to materials, installation technique or perhaps
both?
You mentioned 'shorted' switch . . . were you the
builder who was experiencing fuse popping when the
strobes were turned OFF?
Bob . . .
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Apr 04, 2018 1:37 pm Post subject: Warm Toggle Switch |
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Bob:
You are ALMOST right.
The Rating of a Switch has to do NOT ONLY Voltage and Amperage, but with AC
or DC.
There are different ratings of Amperage for the same switch and physical
size when you talk AC & DC.
An amp is an amp, but, when you deal with the physical size of the switch -
HOW MANY AMPS a switch can handle changes with the type of voltage... All
the way from DC up to RF.
-------------------------------
I think Charlie is directing his email to me?
Charlie England ceengland7(at)gmail.com via
<https://support.google.com/mail/answer/1311182?hl=en> matronics.com
Apr 3 (1 day ago)
Reply
to aeroelectric-l.
Care to show us how you arrive at that last statement, using Ohm's Law?
Barry- It is NOT Ohms Law. There is more to electronics than just Ohms law
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Apr 04, 2018 1:51 pm Post subject: Warm Toggle Switch |
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At 04:35 PM 4/4/2018, you wrote:
| Quote: | Bob:
You are ALMOST right.
The Rating of a Switch has to do NOT ONLY Voltage and Amperage, but with AC or DC.
There are different ratings of Amperage for the same switch and physical size when you talk AC & DC.
An amp is an amp, but, when you deal with the physical size of the switch - HOW MANY AMPS a switch can handle changes with the type of voltage... All the way from DC up to RF. |
Switch WARMING is a function of a switch's
CARRY current. I.e. I(squared)R losses
across the metallic joints I illustrated in
the earlier posting. This energy dissipation
is independent of the nature of system
voltage.
The device's ability to MAKE and BREAK a
circuit is another matter . . . and indeed
is influenced by the nature of system
voltage. This is explained in an article
I published at:
http://aeroelectric.com/articles/Switch_Ratings.pdf
A study of the published ratings from Honeywell
literature supports the notion that the 125VAC
ratings of commercial, off the shelf switches
are on a par with the switch's 14VDC ratings.
Hence my advice to builders over the years suggests
that a hardware store switch rated for 10A at
125VAC was suited to operation in an airplane
at 14VDC.
Bob . . .
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ceengland7(at)gmail.com
Guest
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| Posted: Wed Apr 04, 2018 2:20 pm Post subject: Warm Toggle Switch |
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Yes, I was, but you didn't include in your reply, the line I was asking about. These are DC circuits. Explain how higher resistance causes higher current in a DC circuit. Note that I'm not asking about a switching power supply drawing more current as its supply voltage decreases; I'm asking you to explain how an increase in a DC circuit's resistance causes a higher current to flow in the circuit.
Charlie
On Wed, Apr 4, 2018 at 4:35 PM, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
Â
| Quote: |
I think Charlie is directing his email to me?
Charlie England ceengland7(at)gmail.com (ceengland7(at)gmail.com) via matronics.com Apr 3 (1 day ago)
Reply
to aeroelectric-l.
Care to show us how you arrive at that last statement, using Ohm's Law?
Barry- It is NOT Ohms Law. There is more to electronics than just Ohms law.
0.637 is know as Average.
0.707 is know as RMSÂ (Root Mean Squared)
They are points of power on a Sine Wave.
Example:Â A 110 VAC outlet has MORE that 110 VAC coming out of it.
It is more like 180.07 Volts PEAK.
How much WORK the Peak Voltage can do is AVERAGED to be: Peak x 0.637 = Average.
Or 180.07 x 0.637 = 110 VAC
Now to really confuse ya...
The equivalent of 180.07 VAC in DC would be: Peak x 0.707 = RMS
Or 180.07 x 0.707 = 127.30 VAC
That is why you will see AC ratings ranging from 110 VAC to 130 VAC.
I know, clear as mud.
It is under AC Theory.
Barry
On Tue, Apr 3, 2018 at 11:24 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 08:39 PM 4/2/2018, you wrote:
| Quote: | John:
Yes, the switch may be the problem. Your sw |
itch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps.
 Not so.
 An ampere is equal to flow of 1 Coulomb per second of electrons
 past a point in the conductor. The electrons don't know if they're
 AC, DC or some combination of the two. 1 amp flowing with a force
 of 1 volt for 1 second represents 1 Joule of energy . . . and again,
 this packet of energy knows not from which system it was generated.
 This particular problem with the Carling switches has a history.
 Graybeards on the List will recall a builder's repeated loss
 of the switch that controlled his strobes. Something relaively
 new in the Carling switches saga given that this same style of
 switch had been in service on single engine Cessnas since the
 middle 60's.
 If you consider the physics for conducting Coulombs of electrons
 to the strobes, we can count 10 metallic joints in the
 switch's power path. NONE of those joints can have a resistance
 of ZERO . . . it's ideally small but cannot be zero.
 Four of those joints (1, 2, 9, 10_ are directly acted upon by the
 installer. Two more (3, can be influenced by the installer's
 action when pressing the fast-on terminals into place. Those
 same two joints can be adversely affected by operational
 vibrations of wire bundles too tightly installed to the
 back of switches (short or no service loops in wires).
Â
Â
 All of said joints can be adversely influenced by
 environmental effects and/or manufacturing variations.
 Suffice it to say, any switch that is noticeably
 warm after some time in the ON condition is probably
 suffering a rise in resistance in on or more of the
 10 joints illustrated.
 A change in strobe system design architecture precipitated
 the exchange we had about 10 years ago. You can go to
 the AeroElectric List search feature on
http://www.matronics.com/forums/search.php
 and search on Carling+failure+strobe+rivet
 This was about the time when strobe systems were
 migrating from the legacy Royer oscillator, high
 voltage power supplies to the high efficiency,
 high frequency constant-power supplies. Unlike
 older strobes that drew LESS than normal running
 current at low bus voltage, these systems were
 designed to maintain strobe output at a wide range
 of bus voltages, hence current draw went UP as
 bus voltage goes down.
 Operating strobes on the ground at idle and taxi
 rpms placed extra stress on the switch.
 Here'a a narrative that goes to a particular
 kind of failure in the Carling swtiches:
https://goo.gl/oiZjeG
 I've done teardowns on about a half dozen
 switch failures with locus of the failure
 was seldom repeated.
 Here'a a general article on switch rating
 as it relates to our use of them in airplanes.
https://goo.gl/CPtPYJ
 Yes, the Carling products are inexpensive
 but as Cessna and others have demonstrated for
 decades, this does NOT make them unsuited to
 our tasks. The laws of physics that govern
 their failures are inviolate . . . meaning that
 there are deducible reasons for every failure
 or rash of failures.
 Bob . . .
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alec(at)alecmyers.com
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| Posted: Wed Apr 04, 2018 2:27 pm Post subject: Warm Toggle Switch |
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It’s understandably easy to (incorrectly) jump from TRUE (higher resistance creates more heat) via another TRUE (more current means more heat) to a FALSE:
higher resistance means more current. Of course higher resistance means less current.
Actually higher resistance means less heat overall, but increasing the resistance of one part of a circuit (like a switch) can increase the heat in that spot, causing the trouble.
On Apr 4, 2018, at 18:20, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
Yes, I was, but you didn't include in your reply, the line I was asking about. These are DC circuits. Explain how higher resistance causes higher current in a DC circuit. Note that I'm not asking about a switching power supply drawing more current as its supply voltage decreases; I'm asking you to explain how an increase in a DC circuit's resistance causes a higher current to flow in the circuit.
Charlie
On Wed, Apr 4, 2018 at 4:35 PM, FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)> wrote:
| Quote: |
I think Charlie is directing his email to me?
Charlie England ceengland7(at)gmail.com (ceengland7(at)gmail.com) via matronics.com Apr 3 (1 day ago)
Reply
to aeroelectric-l.
Care to show us how you arrive at that last statement, using Ohm's Law?
Barry- It is NOT Ohms Law. There is more to electronics than just Ohms law.
0.637 is know as Average.
0.707 is know as RMS (Root Mean Squared)
They are points of power on a Sine Wave.
Example: A 110 VAC outlet has MORE that 110 VAC coming out of it.
It is more like 180.07 Volts PEAK.
How much WORK the Peak Voltage can do is AVERAGED to be: Peak x 0.637 = Average.
Or 180.07 x 0.637 = 110 VAC
Now to really confuse ya...
The equivalent of 180.07 VAC in DC would be: Peak x 0.707 = RMS
Or 180.07 x 0.707 = 127.30 VAC
That is why you will see AC ratings ranging from 110 VAC to 130 VAC.
I know, clear as mud.
It is under AC Theory.
Barry
On Tue, Apr 3, 2018 at 11:24 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 08:39 PM 4/2/2018, you wrote:
| Quote: | John:
Yes, the switch may be the problem. Your sw |
itch S700-1-3 is a 15 Amp rating on AC. Which is NOT 15 Amps on DC. A good rule of thumb is the switch should be able to handle DOUBLE the DC amperage that the circuit draws. There are a couple of ways of determining the DC rating of an AC Switch. You can say take .707 x Rating or .637 x Rating. So: 15 Amps x .707 = 10.6 Amps // or 15 Amps x .637 = 9.5 Amps.
Not so.
An ampere is equal to flow of 1 Coulomb per second of electrons
past a point in the conductor. The electrons don't know if they're
AC, DC or some combination of the two. 1 amp flowing with a force
of 1 volt for 1 second represents 1 Joule of energy . . . and again,
this packet of energy knows not from which system it was generated.
This particular problem with the Carling switches has a history.
Graybeards on the List will recall a builder's repeated loss
of the switch that controlled his strobes. Something relaively
new in the Carling switches saga given that this same style of
switch had been in service on single engine Cessnas since the
middle 60's.
If you consider the physics for conducting Coulombs of electrons
to the strobes, we can count 10 metallic joints in the
switch's power path. NONE of those joints can have a resistance
of ZERO . . . it's ideally small but cannot be zero.
Four of those joints (1, 2, 9, 10_ are directly acted upon by the
installer. Two more (3, can be influenced by the installer's
action when pressing the fast-on terminals into place. Those
same two joints can be adversely affected by operational
vibrations of wire bundles too tightly installed to the
back of switches (short or no service loops in wires).
All of said joints can be adversely influenced by
environmental effects and/or manufacturing variations.
Suffice it to say, any switch that is noticeably
warm after some time in the ON condition is probably
suffering a rise in resistance in on or more of the
10 joints illustrated.
A change in strobe system design architecture precipitated
the exchange we had about 10 years ago. You can go to
the AeroElectric List search feature on
http://www.matronics.com/forums/search.php
and search on Carling+failure+strobe+rivet
This was about the time when strobe systems were
migrating from the legacy Royer oscillator, high
voltage power supplies to the high efficiency,
high frequency constant-power supplies. Unlike
older strobes that drew LESS than normal running
current at low bus voltage, these systems were
designed to maintain strobe output at a wide range
of bus voltages, hence current draw went UP as
bus voltage goes down.
Operating strobes on the ground at idle and taxi
rpms placed extra stress on the switch.
Here'a a narrative that goes to a particular
kind of failure in the Carling swtiches:
https://goo.gl/oiZjeG
I've done teardowns on about a half dozen
switch failures with locus of the failure
was seldom repeated.
Here'a a general article on switch rating
as it relates to our use of them in airplanes.
https://goo.gl/CPtPYJ
Yes, the Carling products are inexpensive
but as Cessna and others have demonstrated for
decades, this does NOT make them unsuited to
our tasks. The laws of physics that govern
their failures are inviolate . . . meaning that
there are deducible reasons for every failure
or rash of failures.
Bob . . .
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Apr 04, 2018 3:16 pm Post subject: Warm Toggle Switch |
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Bob:
" Â A study of the published ratings from Honeywell
 literature supports the notion that the 125VAC
 ratings of commercial, off the shelf switches
 are on a par with the switch's 14VDC ratings.
 Hence my advice to builders over the years suggests
 that a hardware store switch rated for 10A at
 125VAC was suited to operation in an airplane
 at 14VDC.
 Bob . . ."
What do you consider "on a par with..." One can go to just about any electronics catalog and look up a switch with dual ratings and you will ALWAYS find the DC Amperage is lower than the AC Amperage of that same switch. Â
The point(s) I was making were:Â Â
1 - There are many reasons why John's switch can be getting warm.
2 - A poorly chosen switch can be one of those reasons. Not that John chose the switch, it could have been recommended by the instructions. After all it lasted for 9+ years.
3 - Maybe it was just its time to DIE!
4 - How the plane is stored? Hanger? Outside? High Humidity?
5 - Poor connections ie: Fast-On connectors, No Lock Washer, Undersized Wire, etc.
6 - Vibration! ALL planes suffer from Vibration. My rule of thumb is: For every hour you fly, there is 4 hours of maintenance.
And one of my Favorites:
7 - Chinese JUNK!
MANY components are NOT what the SAY they are!
Just because it is stamped 10 Amps does not mean it is 10 Amps. And when working close to the edge of specifications one is taking a chance. On a switch that is rated at 9 / 10 Amps and the circuit draws 7.5 Amps. That is not good design practice.
One of my tricks is to use a DPST switch and tie both sides to the same circuit. The rating for a DP switch is for each side. So, by tying them together you DOUBLE the rating, As well as doubling the physical properties of the switch. Â
Funny thing in engineering: When you design for the COMPANY you design with the pocketbook in mind. When you design for yourself and especially for your OWN plane... To HELL with the pocketbook! I don't ever want to repair that Dang Circuit Again! It was HELL to get at!!! So, yes, we will put in a $4.00 switch instead of that $2.35 Chinese Switch. The COMPANY won't... But, I will!!!
Barry
On Wed, Apr 4, 2018 at 5:51 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 04:35 PM 4/4/2018, you wrote:
| Quote: | Bob:
You are ALMOST right.
The Rating of a Switch has to do NOT ONLY Voltage and Amperage, but with AC or DC.
There are different ratings of Amperage for the same switch and physical size when you talk AC & DC.
An amp is an amp, but, when you deal with the physical size of the switch - HOW MANY AMPS a switch can handle changes with the type of voltage... All the way from DC up to RF. |
 Switch WARMING is a function of a switch's
 CARRY current. I.e. I(squared)R losses
 across the metallic joints I illustrated in
 the earlier posting. This energy dissipation
 is independent of the nature of system
 voltage.
 The device's ability to MAKE and BREAK a
 circuit is another matter . . . and indeed
 is influenced by the nature of system
 voltage. This is explained in an article
 I published at:
http://aeroelectric.com/articles/Switch_Ratings.pdf
 A study of the published ratings from Honeywell
 literature supports the notion that the 125VAC
 ratings of commercial, off the shelf switches
 are on a par with the switch's 14VDC ratings.
 Hence my advice to builders over the years suggests
 that a hardware store switch rated for 10A at
 125VAC was suited to operation in an airplane
 at 14VDC.
 Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Apr 04, 2018 4:38 pm Post subject: Warm Toggle Switch |
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| Quote: |
What do you consider "on a par with..." One can go to just about any electronics catalog and look up a switch with dual ratings and you will ALWAYS find the DC Amperage is lower than the AC Amperage of that same switch.
|
What statement in the article I cited was questionable?
Did you read the article?
I cited a ratings chart purloined directly from the Honeywell/Microswich
catalog which I repeat here:
[img]cid:.0[/img]
I observe that for a switch with any particular
"electrical code rating" the 115 VAC ratings are
not seriously different from 28VDC ratings. I further
deduced that 14VDC ratings should be equal to or better
than 28VDC ratings.
Consider a switch of code 3:
115 vac resistive 15A
28 vdc resistive 20A
Why would such a switch not be comfortably incorporated into
a 14VDC system working a 20A load?
Take any OTHER rating and cite the situation where the
builder's choice of switches is at-risk for using the
device?
Further, assume that a switch is incorporated into
a 14VDC system at say 3x the switch's 'ratings'.
What are the likely effects for such oversight?
How would a 3x 'overload' affect service life? Given
that most lightplanes fly 50 hours per year, assiming
two switch operations per flight hour, what might we
expect for service longevity of this 'severely' overloaded
switch?
Forgive me, that's a loaded question. Referring to the
the chart above, the 'severely overloaded' switch would
would have to be applied in a circuit that controls at
least 15 x 3 or 45 amps. No such system exists in light
aircraft where such currents flow in crew operated switches.
The point to be considered here is that the 'warm switch'
in question has an easily deduced root cause based on
simple physics and the extensive experience base for
members of this List.
| Quote: | The point(s) I was making were:Â Â
1 - There are many reasons why John's switch can be getting warm.
2 - A poorly chosen switch can be one of those reasons. Not that John chose the switch, it could have been recommended by the instructions. After all it lasted for 9+ years.
3 - Maybe it was just its time to DIE!
4 - How the plane is stored? Hanger? Outside? High Humidity?
5 - Poor connections ie: Fast-On connectors, No Lock Washer, Undersized Wire, etc.
6 - Vibration! ALL planes suffer from Vibration. My rule of thumb is: For every hour you fly, there is 4 hours of maintenance.
And one of my Favorites:
7 - Chinese JUNK! |
Whoa!!! You've thrown the kitchen sink into the discussion.
One of the goals for this List is to combine a knowledge of
history with a good grasp on the simple ideas in physics
viewed through a narrow-spectrum lens of demonstrable cause/effect.
In what way has anything I've offered in this thread conflicted
with physics and/or 50 years experience/lessons-learned?
You have asserted that some instances of INCREASED resistance
can manifest as an INCREASED current. I'm mystified by this
assertion . . . yet if correct . . . is easily demonstrated.
Can you shoot a video on you mobile phone for any assortment
of components powered from a source of your choice where
INCREASING a resistance INCREASES current.
If we've mis-interpreted your words, then you have my
profound apologies . . . we only seek to understand.
Bob . . .
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ChasB(at)satx.rr.com
Guest
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| Posted: Thu Apr 05, 2018 6:22 am Post subject: Warm Toggle Switch |
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Time: 08:45:12 AM PST USFrom: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>Subject: Re: Warm Toggle SwitchAt 09:21 AM 4/4/2018, you wrote: | Quote: | | I went through several warm, hot, and/or shorted switches that operated my strobes. Tried several brands of switches all with the same results. Finally trouble shot the whole system and found a bad connector crimp on the positive wire that connected at the strobe power pack. Repaired same, and haven=99t had a switch problem since. |
What were your observations for condition of the materials at the failure . . . and do you recall whether the failure was related to materials, installation technique or perhaps both? You mentioned 'shorted' switch . . . were you the builder who was experiencing fuse popping when the strobes were turned OFF? Bob . . .
——————————————————-
Bob, et., al.,
I did have a popped fuse or so, but I don’t think they were related to the shorted switch. The shorted switch toggle itself was electrified when either on or off. On various switches, I found loose connectors, corroded and failed contacts, and in one case, the plastic switch case was partially melted from the heat. Failures were probably related to both materials and installation technique. I’m not sure all the problems were related to the bad strobe pack connection, but fixing that seems to have solved the problems.
Charlie
RV-6A, N11CB
San Antonio
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Thu Apr 05, 2018 7:31 am Post subject: Warm Toggle Switch |
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Good Find Charlie;
Sure sounds like your switch did one of two things or maybe even BOTH:
1 - WELDED the contacts closed and/or,
2 - Mechanically Failed.
The mechanical failure could also have been due to the contacts being Welded and when you flip the switch, the weld being stronger than the pivot points of the switch... Ergo, the switch broke!
Question: Is the switch WHITE in color? Except for the burnt areas of course?
Poor contact(s) ANYWHERE in the circuit increase current draw. The weak point being the switch.
ARKENSPARKÂ - - ARKENFARK
Hope my original post was helpful.
Barry
On Thu, Apr 5, 2018 at 10:21 AM, Charles Brame <ChasB(at)satx.rr.com (ChasB(at)satx.rr.com)> wrote:
| Quote: | Time: 08:45:12 AM PST USFrom: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>Subject: Re: Warm Toggle SwitchAt 09:21 AM 4/4/2018, you wrote: | Quote: | I went through several warm, hot, and/or shortedÂ
switches that operated my strobes. Tried severalÂ
brands of switches all with the same results.Â
Finally trouble shot the whole system and foundÂ
a bad connector crimp on the positive wire thatÂ
connected at the strobe power pack. RepairedÂ
same, and haven=99t had a switch problem since.
|
  What were your observations for condition of  the materials at the failure . . . and do  you recall whether the failure was related  to materials, installation technique or perhaps  both?  You mentioned 'shorted' switch . . . were you the  builder who was experiencing fuse popping when the  strobes were turned OFF?  Bob . . .Â
——————————————————-
Bob, et., al.,
I did have a popped fuse or so, but I don’t think they were related to the shorted switch. The shorted switch toggle itself was electrified when either on or off. On various switches, I found loose connectors, corroded and failed contacts, and in one case, the plastic switch case was partially melted from the heat. Failures were probably related to both materials and installation technique. I’m not sure all the problems were related to the bad strobe pack connection, but fixing that seems to have solved the problems.
Charlie
RV-6A, N11CB
San Antonio
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Eric Page
Joined: 15 Feb 2017
Posts: 247
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| Posted: Thu Apr 05, 2018 9:53 am Post subject: Re: Warm Toggle Switch |
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| BARRY CHECK 6 wrote: | | Poor contact(s) ANYWHERE in the circuit increase current draw. |
Generally speaking, this is incorrect. A poor contact increases resistance. Increased resistance causes a decrease in current through a circuit.
The exception is an appliance using an internal switching power supply, which functions as a constant power device, drawing whatever combination of voltage and current it can manage to maintain the required output. This is most likely to be seen powering modern avionics and high power LEDs (i.e. landing lights and strobe drivers).
For everything else — lighting circuits, motors, pumps, heaters and anything with linear voltage regulation — the resistance/voltage/current relationship must follow Ohm’s Law.
Eric
P.S. On Internet forums, the use of ALL CAPS is considered equivalent to shouting. If you’re posting via email rather than the web interface where bold, italics and underline are available, consider sparing use of *asterisks* before and after words you wish to emphasize.
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