Today's Message Index:
----------------------
1. 06:20 AM - Re: 1 Amp Fuses (Richard Girard)
2. 07:35 AM - Re: 1 Amp Fuses (Michael T. Ice)
3. 09:56 AM - Re: 1 Amp Fuses (Fiveonepw@aol.com)
4. 02:45 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III)
5. 03:43 PM - Re: 1 Amp Fuses (Dennis Golden)
6. 06:09 PM - Re: 1 Amp Fuses (Terry Miles)
7. 07:13 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III)
8. 07:15 PM - Re: 1 Amp Fuses (Robert L. Nuckolls, III)
9. 07:18 PM - 1 AMP Fuses (Ralph Hoover)
Message 1
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Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.
Rick
On 9/11/07, Michael Petersen <mpetersen@repsol.com.au> wrote:
>
> G'day Bob and List Members,
>
>
> I have come across a number of equipment manufacturers that specify a 1
> amp fuse for their equipment (eg Ray Allen trim systems) and I am using a
> mini blade type fuse block in my aircraft. The smallest fuse I can find is 2
> amps, which leads me towards the following alternatives;
>
>
> 1. Stick to the philosophy of selecting the fuse to suit the wire
> (22awg in this case) and ignoring the manufacturer's requirement.
> 2. Use the 2 amp blade fuse, being the closest available.
> 3. Incorporating some other type of 1 amp circuit protection, for
> example a small circuit board being supplied via the main bus/fuse block
> that provides several 1 amp circuits protected by a PTC type fuse.
>
>
> My question is, is there a recognized 'correct' way of dealing with this
> issue, or what is the preferred solution?
>
>
> Bob, I have read your critique of Greg Richter's "Aircraft Wiring for
> Smart People", in which you very briefly mention that PTC fuses are not
> suitable for use in aircraft. Could you please elaborate on your research
> and findings? By the way, I am half way through reading your book and would
> like to thank you for the effort you put into helping people like me
> understand these issues! Keep up the good work!
>
>
> Thanks,
>
>
> Michael
>
>
> *
>
>
> *
>
>
--
Rick Girard
"Ya'll drop on in"
takes on a whole new meaning
when you live at the airport.
Message 2
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Michael,
Tech-Tips
PTC's vs. Fuses
PTC's act as a type of circuit breaker; the resistance increases as the PTC
threshold temperature is exceeded due to the load current passing through the
device. This causes high resistance which opens the circuit protecting the
device in the event of an over current condition. Unlike fuses, ambient temperature
plays a role in how long it will be before a PTC reacts to over current.
For this reason, careful consideration should be given to when PTC's are used
for equipment protection.
A PTC is appropriate for battery protection as most battery shorts are heavy
shorts quickly tripping the PTC. The PTC is best for devices that can tolerate
high current for a substantial amount of time, such as batteries.
Because PTC's are slow acting and have a less accurate trip threshold, the
PTC may not protect the cameras as reliably as a fast acting fuse. Because PTC's
need to cool down to reset and will not do so if the over current condition
is not corrected, a service call will probably be needed to address the failure.
A one amp PTC may never blow at 2 amps and may require more than 30 seconds
to blow at 5 amps. A one-amp fuse should blow at 1.25 amps in about 1 second,
regardless of conditions. It is much more economical for the dealer/customer
to replace a simple fuse rather than an expensive piece of electronics.
This came off of the: www.pthree.com/techtips.aspx
Doesn't seem like the PTC is a good idea.
Mike
----- Original Message -----
From: Michael Petersen
To: aeroelectric-list@matronics.com
Sent: Tuesday, September 11, 2007 8:00 PM
Subject: AeroElectric-List: 1 Amp Fuses
G'day Bob and List Members,
I have come across a number of equipment manufacturers that specify a 1 amp fuse
for their equipment (eg Ray Allen trim systems) and I am using a mini blade
type fuse block in my aircraft. The smallest fuse I can find is 2 amps, which
leads me towards the following alternatives;
1.. Stick to the philosophy of selecting the fuse to suit the wire (22awg in
this case) and ignoring the manufacturer's requirement.
2.. Use the 2 amp blade fuse, being the closest available.
3.. Incorporating some other type of 1 amp circuit protection, for example
a small circuit board being supplied via the main bus/fuse block that provides
several 1 amp circuits protected by a PTC type fuse.
My question is, is there a recognized 'correct' way of dealing with this issue,
or what is the preferred solution?
Bob, I have read your critique of Greg Richter's "Aircraft Wiring for Smart People",
in which you very briefly mention that PTC fuses are not suitable for
use in aircraft. Could you please elaborate on your research and findings? By
the way, I am half way through reading your book and would like to thank you for
the effort you put into helping people like me understand these issues! Keep
up the good work!
Thanks,
Michael
Message 3
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In a message dated 09/11/2007 10:58:26 PM Central Daylight Time,
mpetersen@repsol.com.au writes:
Stick to the philosophy of selecting the fuse to suit the wire (22awg in this
case)
Yes. 2-amp fuse would be fine, IMHO.
Mark do not archive
Message 4
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At 08:18 AM 9/12/2007 -0500, you wrote:
>Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.
>
>Rick
B&C stocks them too.
If you do a google search on "ATC-1" and "fuse" you'll
find lots of other folks have them too.
Bob . . .
Message 5
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Robert L. Nuckolls, III wrote:
> <nuckolls.bob@cox.net>
>
> At 08:18 AM 9/12/2007 -0500, you wrote:
>
>> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.
>>
>> Rick
>
> B&C stocks them too.
>
> If you do a google search on "ATC-1" and "fuse" you'll
> find lots of other folks have them too.
I thought the original post stated that the fuse box was for miniature
(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also.
Dennis
--
Dennis Golden
Golden Consulting Services, Inc.
Message 6
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Just to toss a little more in the mix about fuses. I bought a box of fuses
from Harbor Freight about a year ago and went back today for another box.
Their ATC (ATO?) sized (the middle size ones that most of us use) have been
recalled. Nobody knew any of the circumstances around this decision. I
thought everyone ought to know.
Terry
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dennis
Golden
Sent: Wednesday, September 12, 2007 6:43 PM
Subject: Re: AeroElectric-List: 1 Amp Fuses
<dgolden@golden-consulting.com>
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@cox.net>
>
> At 08:18 AM 9/12/2007 -0500, you wrote:
>
>> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.
>>
>> Rick
>
> B&C stocks them too.
>
> If you do a google search on "ATC-1" and "fuse" you'll
> find lots of other folks have them too.
I thought the original post stated that the fuse box was for miniature
(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also.
Dennis
--
Dennis Golden
Golden Consulting Services, Inc.
Message 7
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At 05:42 PM 9/12/2007 -0500, you wrote:
><dgolden@golden-consulting.com>
>
>Robert L. Nuckolls, III wrote:
> > <nuckolls.bob@cox.net>
> >
> > At 08:18 AM 9/12/2007 -0500, you wrote:
> >
> >> Michael, Stein Air has 1 amp blade fuses, PN SA-201, $.30 ea.
> >>
> >> Rick
> >
> > B&C stocks them too.
> >
> > If you do a google search on "ATC-1" and "fuse" you'll
> > find lots of other folks have them too.
>
>I thought the original post stated that the fuse box was for miniature
>(i.e. ATM) fuses. I've had problems finding anything less that 2 amp also.
Opps. My bad. Yes, the ATM spec sheet
http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATM_Specs.pdf
says 2A is as small as they go in that form-factor unlike
the ATC sheet
http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATC_Specs.pdf
which takes us down to 1A. I didn't go back to the original
post. Sooooo . . .
G'day Bob and List Members,
I have come across a number of equipment manufacturers that specify
a 1 amp fuse for their equipment (eg Ray Allen trim systems) and
I am using a mini blade type fuse block in my aircraft. The smallest
fuse I can find is 2 amps, which leads me towards the following
alternatives;
Stick to the philosophy of selecting the fuse to suit the wire
(22awg in this case) and ignoring the manufacturer's requirement.
Use the 2 amp blade fuse, being the closest available.
This would probably be just fine. I've always had a bit
of heartburn about manufacturer's "suggestions" that
their device would benefit from some degree of protection
by installation . . . which the installer is expected to
supply. Having said that - I HAVE designed systems using
appliances with very light draw (under 1A) where
their 22AWG feeders were protected with small fuses. This
is pretty easy when the system is wired with the ATC
fuseblocks. Harder as you've noted in alternative
fuseblock products.
Incorporating some other type of 1 amp circuit protection, for
example a small circuit board being supplied via the main bus/fuse
block that provides several 1 amp circuits protected by a PTC type fuse.
The 2A fuse will be fine. As you've already noted, the
PTC is not easily integrated into a system. The small,
solid wire lead components are designed to be integrated
inside a device and demand some appliance design,
fabrication and installation (i.e., super-whippy power
distribution assembly boards).
My question is, is there a recognized 'correct' way of dealing with
this issue, or what is the preferred solution? Bob, I have read your
critique of Greg Richter's "Aircraft Wiring for Smart People",
in which you very briefly mention that PTC fuses are not suitable
for use in aircraft. Could you please elaborate on your research
and findings?
I'm not sure I've ever used the words "not suitable" but
there have been many a discussion between myself an individuals
who were touting products that incorporated the PTC (aka polyswitch,
and polyfuse). A few documents in addition to the Richter discussion
include:
http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf
http://www.aeroelectric.com/articles/expbusthd.html
http://www.aeroelectric.com/articles/expbusad.html
The polyswitch was first presented to me about 1982 by my
very good friend Jim West who at the time was a Raychem
rep with Thunderbird aviation. I had the electrical/
avionics group on the GP-180 and Jim thought perhaps
this nifty device would find useful applications in
the airframe arena.
First, let me be quite clear that incorporation of
the polyswitch NEVER raised questions with respect to
safety. It was never pushed aside for failure to do the
tasks that fuses, breakers and other FIRE PROTECTION devices
have accomplished for over a century.
The questions about PTC circuit protection have to
do with (1) $value$ of the trade-off and (2) integration
into the overall system design philosophy.
PTC's are loose components intended to solder to an
etched circuit board. This means that unlike a collection
of fuses or breakers (which are easily integrated into
a wide variety of designs as individual components)
an array of PTC devices becomes an appliance - an
assembly that in the TC aircraft world requires
qualification. Those qualification test would most
certainly include vibration and operation over temperature
extremes.
In the OBAM aircraft world, the appliance grows features
like pre-assembled switch panels, avionics bus noise
filters and power management, voltage regulators, etc.
The more features that are added, the less adaptable
becomes the appliance. What you see is what you get . . .
take it or leave it. And whether or not you want or
need all those features, the cost is not insignificant.
In the TC world, I participated in three explorations
with others. Once at Learjet and twice at Beech to
see if the PTC offered any features attractive to
our program managers and customers . . . and the FAA.
Had more than one FAA type objecting to the "self re-setting
feature of PTCs . . . when a hazardous fault operates
the circuit protection, present conventions call for
the system to open and stay open pending repairs.
Many have read my writings about the various products
that feature PTCs and have mis-interpreted the down-side
observations to be an attack on PTCs as protective
devices. Again, they do the job they were designed to
do in the manner described in their sales literature.
The BIG picture speaks to poor $value$ and loss of some
operational and architecture control when appliances
(perhaps combined with other components) are used to
replace loose breakers or inexpensive fuseblocks.
By the way, I am half way through reading your book and would like
to thank you for the effort you put into helping people like me
understand these issues! Keep up the good work!
You HAVE already thanked me by purchasing the work. I'm
pleased that you're finding it useful.
Bob . . .
Message 8
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At 09:06 PM 9/12/2007 -0400, you wrote:
><terrence_miles@hotmail.com>
>
>Just to toss a little more in the mix about fuses. I bought a box of fuses
>from Harbor Freight about a year ago and went back today for another box.
>Their ATC (ATO?) sized (the middle size ones that most of us use) have been
>recalled. Nobody knew any of the circumstances around this decision. I
>thought everyone ought to know.
>Terry
A number of wanna-be's in the fuse business have attempted to
clone the ATC and similar products only to find that the
simple little fuse was more complex than molding some handy
metal stamping inside a plastic housing. Folks like Cooper-
Bussman and Littlefuse have been in this business for a
very long time and have optimized the recipe for success
in the creation of a product that performs as advertised.
You're never treading at the edge by purchasing devices
with these brands on them.
Bob . . .
Message 9
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Littlefuse lists 1A minimum in the 257 series ATO fuses and 2A minimum
in the 297 mini series.
--
Ralph C. Hoover
RV7A
hooverra at verizon dot net
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