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richardreynolds(at)cox.ne
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 Posted: Thu Dec 12, 2013 11:04 am Post subject: Switches Redux |
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Bob,
Application, RC model airplane, receiver-servos, 6V - 2100 mAh NiMH battery, 150 mA idle, 6A max intermittent.
The battery is connected to the receiver-servos throughout an off-on switch (SPDT).
Which switch is more reliable, mini toggle or a mini slide?
For power (6A) (versus data), which contacts are more reliable, gold or silver? Both have a contact resistance of about 10 mOhms.
Is any brand more reliable?
A bad switch in flight will cause a bay day on the ground.
Richard Reynolds
B-47E 1/12 Scale Model Project
[img]cid:21541C7A-6677-4702-AB4F-CE530DF0C1C8(at)hr.cox.net[/img][img]cid:0AEC9479-391F-4822-AC2F-D2395D891672(at)hr.cox.net[/img]
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jluckey(at)pacbell.net
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| Posted: Thu Dec 12, 2013 12:25 pm Post subject: Switches Redux |
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Richard,
It's been my experience that the slider type switch is more reliable for R/C applications because it seems to be more resistant to high-frequency vibrations common in R/C aircraft.
I asked the same question and went thru some analysis back in the 90's for some of my giant scale aerobatic ships and the consensus at that time was sliders were better for this application. I think that's why all radio manufacturers supply their systems w/ sliders. I don't think that I've ever seen an after-market switch harness that was anything other than a slider.
-Jeff
From: Richard Reynolds <richardreynolds(at)cox.net>
To: AeroElectric AeroElectric <aeroelectric-list(at)matronics.com>
Sent: Thursday, December 12, 2013 11:03 AM
Subject: Switches Redux
Bob,
Application, RC model airplane, receiver-servos, 6V - 2100 mAh NiMH battery, 150 mA idle, 6A max intermittent.
The battery is connected to the receiver-servos throughout an off-on switch (SPDT).
Which switch is more reliable, mini toggle or a mini slide?
For power (6A) (versus data), which contacts are more reliable, gold or silver? Both have a contact resistance of about 10 mOhms.
Is any brand more reliable?
A bad switch in flight will cause a bay day on the ground.
Richard Reynolds
B-47E 1/12 Scale Model Project
[img]cid:1.1426965065(at)web184904.mail.gq1.yahoo.com[/img][img]cid:2.1426965065(at)web184904.mail.gq1.yahoo.com[/img]
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nuckolls.bob(at)aeroelect
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| Posted: Thu Dec 12, 2013 12:44 pm Post subject: Switches Redux |
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At 01:03 PM 12/12/2013, you wrote:
Bob,
Application, RC model airplane, receiver-servos,
6V - 2100 mAh NiMH battery, 150 mA idle, 6A max intermittent.
The battery is connected to the receiver-servos throughout
an off-on switch (SPDT).
Which switch is more reliable, mini toggle or a mini slide?
For power (6A) (versus data), which contacts are more reliable,
gold or silver? Both have a contact resistance of about 10 mOhms.
Is any brand more reliable?
Richard,
Are you aware of modelers who have lost an
airplane due to failure of a receiver power
source? In the pyramid of design requirements,
what is the weakest link in your system wherein
a failure becomes catastrophic?
If you've identified the switch as a high-order
concern, then 'reliability' of any mechanical
device is probably driven more by environmental
concerns than electrical ratings. What kinds
of contaminants might get into the switch and
degrade performance. Is vibration an issue?
Gold contacts insure performance for contacts
that need to work at very low current levels . . .
levels too low to burn away contaminants on
silver-cad contacts by virtue of arcing that
occurs in normal operation.
The silver-cad contacts are probably better
suited to your task. If you want the ultimate
in reliability, perhaps all solid state offers
a solution. A high side switch biased to an
ON-state with a Hall-effect switch. The Hall
being magnetically excited by a "key" inserted
to position a magnet.
The 'works' for this switch would mount on an
ECB about 1/2" x 3/4". It would take some mechanical
fiddly-diddly to mount and integrate with
the 'key'.
Depending on the bounds of your worry and
experiences of others, there's a constellation
of approaches. A toggle is probably positionally
more secure than a slide and is probably fitted
with real silver-cad contacts as opposed to
un-plated brass innards common to slide switches.
Sorry not to have a definitive response but
I'm sure that there are means for addressing
your worst concerns.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Thu Dec 12, 2013 1:32 pm Post subject: Switches Redux |
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At 02:24 PM 12/12/2013, you wrote:
Richard,
It's been my experience that the slider type switch is more reliable
for R/C applications because it seems to be more resistant to
high-frequency vibrations common in R/C aircraft.
I asked the same question and went thru some analysis back in the
90's for some of my giant scale aerobatic ships and the consensus at
that time was sliders were better for this application. I think
that's why all radio manufacturers supply their systems w/
sliders. I don't think that I've ever seen an after-market switch
harness that was anything other than a slider.
-Jeff
It would be interesting to know the physics
behind any assertions for superior vibration
resistance in a slide switch. It kinda argues
with what we know about the construction of
the two technologies.
The moving contact in a slider is generally
forced against stationary contacts by a
compression spring centered on the moving
contact. This means that vibration normal
to the plane of the stationary contacts
would work on the center of gravity for the
moving contact directly against the spring
pressure. It follows that when acceleration
exceeds slider mass x force . . . Sir Isaac's
Second law . . . discontinuities in the switch
can be expected.
In a toggle switch, the moving contact is a
"teeter-totter" who's cg is located on the
pivot of the mechanism. A spring presses the
teeter-totter down against a stationary contact
to one or the other side of the pivot to
effect the switching behavior.
Acceleration of the switch assembly normal
to the plane of the stationary contacts once
again acts on the c.g. of the moving contact
which is located at the center . . . and balanced
by equal masses on both sides of the pivot.
The switch actuator spring adds a force on
the 'closed' side of the switch, a force which,
by virtue of that balance, is not opposed by
the forces of acceleration.
See http://tinyurl.com/noo8odx
I'm having trouble visualizing how a toggle
could be more prone to vibration induced
disconnect. You have to get into mil-spec
switches before the manufacturer's even offer
much in the way of vibration data. The few
switches I found with vibration ratings on
their data sheets only spoke to effect of
less than 100Hz . . .
I'm wondering what is meant by 'high frequency'
vibration characteristic of model airplanes.
It's true that slide switches have been
VERY popular with the R/C crowd . . . that's
the only style of switch I observed on the
rudder-only models of my youth. But then,
that was long before the miniature toggle switch
even came along.
I'm not perceiving any foundation in physics
for giving points to slide switches in the
vibration game. I've yet to find any manufacturer's
data that offers a comparison of vibration
effects beyond that which I've hypothesized
above.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Dec 12, 2013 2:20 pm Post subject: Switches Redux |
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oops!!!! When Acceleration exceeds spring force/slider mass
. . . Sir Isaac's Second law . . . discontinuities in
the switch can be expected . . . sorry Sir Isaac!
Bob . . . [quote][b]
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jluckey(at)pacbell.net
Guest
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| Posted: Thu Dec 12, 2013 2:23 pm Post subject: Switches Redux |
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I dunno Bob, it's just the way they've done it for the past 40+ years. <grin>
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Thursday, December 12, 2013 1:31 PM
Subject: Re: Switches Redux
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
At 02:24 PM 12/12/2013, you wrote:
Richard,
It's been my experience that the slider type switch is more reliable for R/C applications because it seems to be more resistant to high-frequency vibrations common in R/C aircraft.
I asked the same question and went thru some analysis back in the 90's for some of my giant scale aerobatic ships and the consensus at that time was sliders were better for this application. I think that's why all radio manufacturers supply their systems w/ sliders. I don't think that I've ever seen an after-market switch harness that was anything other than a slider.
-Jeff
It would be interesting to know the physics
behind any assertions for superior vibration
resistance in a slide switch. It kinda argues
with what we know about the construction of
the two technologies.
The moving contact in a slider is generally
forced against stationary contacts by a
compression spring centered on the moving
contact. This means that vibration normal
to the plane of the stationary contacts
would work on the center of gravity for the
moving contact directly against the spring
pressure. It follows that when acceleration
exceeds slider mass x force . . . Sir Isaac's
Second law . . . discontinuities in the switch
can be expected.
In a toggle switch, the moving contact is a
"teeter-totter" who's cg is located on the
pivot of the mechanism. A spring presses the
teeter-totter down against a stationary contact
to one or the other side of the pivot to
effect the switching behavior.
Acceleration of the switch assembly normal
to the plane of the stationary contacts once
again acts on the c.g. of the moving contact
which is located at the center . . . and balanced
by equal masses on both sides of the pivot.
The switch actuator spring adds a force on
the 'closed' side of the switch, a force which,
by virtue of that balance, is not opposed by
the forces of acceleration.
See http://tinyurl.com/noo8odx
I'm having trouble visualizing how a toggle
could be more prone to vibration induced
disconnect. You have to get into mil-spec
switches before the manufacturer's even offer
much in the way of vibration data. The few
switches I found with vibration ratings on
their data sheets only spoke to effect of
less than 100Hz . . .
I'm wondering what is meant by 'high frequency'
vibration characteristic of model airplanes.
It's true that slide switches have been
VERY popular with the R/C crowd . . . that's
the only style of switch I observed on the
rudder-only models of my youth. But then,
that was long before the miniature toggle switch
even came along.
I'm not perceiving any foundation in physics
for giving points to slide switches in the
vibration game. I've yet to find any manufacturer's
data that offers a comparison of vibration
effects beyond that which I've hypothesized
above.
Bobsp; -- Please Support Your Lists tric www.aeroele"_blank" href="http://www.buildersbooks.com/">www.buildersbooks.comww-======================== --> http://f=======================
[quote][b]
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