Today's Message Index:
----------------------
1. 05:19 AM - Re: Power Duece Schottky diodes (Christopher Cee Stone)
2. 06:19 AM - Re: mystery relay (user9253)
3. 05:05 PM - Re: Re: New role for the E-Bus? (Robert L. Nuckolls, III)
4. 06:23 PM - Re: Re: New role for the E-Bus? (Charlie England)
5. 07:16 PM - Re: Power Duece Schottky diodes (Randy C-GRPY)
Message 1
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| Subject: | Re: Power Duece Schottky diodes |
Beware of counterfeit semiconductors on EBay...
https://www.electro-tech-online.com/blog-entries/watch-out-for-counterfeit-transistors.78
I purchased some 2N3055 power bipolors. cut them open and they were
counterfeit. Tiny die compared to the original STMicro parts. This may be
the case when you see bargain low ball prices for other semiconductors.
The modus operandi seems to be to re label parts that look identical to the
original but are of lower power higher noise spec.
Chris
RV-8 twice
On Sat, Feb 22, 2020 at 10:17 AM Charlie England <ceengland7@gmail.com>
wrote:
>
>
> On Sat, Feb 22, 2020 at 11:14 AM Randy C-GRPY <rpulis@shaw.ca> wrote:
>
>>
>> I want dual diodes to feed alternate power to critical components with
>> only one power input. The ones sold by Perihelion Designs seem to fit the
>> bill well but are quite pricey. Are they worth the cost or are there
>> equally good, cheaper solutions to be considered?
>>
>> Thanks
>> Randy
>>
>>
> There are hundreds of choices on ebay, at prices all over the map (even
> for the same device). ex: The stps12045tv is a dual 60A 45V device with an
> electrically isolated base (simpler mounting) that can be found for as much
> as $75, or as little as 2 for $12, if you're willing to wait a few weeks
> for them to arrive from China. Mouser (major electronics supplier) has them
> for $20. If you spend more time searching, you might find some even
> cheaper; I did several months ago.
>
> If you don't need that much current, you can get a whole bag of them for
> less than $10 in some cases. Do exercise caution when mounting any metal
> tabbed device, to be sure the tab isn't electrically common to one of the
> leads. When browsing, just look for voltage above ~20V, at whatever current
> you need. Remember that current ratings assume significant heat sinking; if
> you want to avoid mounting on a heat sink, just oversize the device
> significantly for the job. A legit heat sink will probably cost a lot more
> than upsizing the device. :-)
>
> https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=dual+schottky+diode&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=stps12045tv
>
>
Message 2
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| Subject: | Re: mystery relay |
The current rating of a relay has been determined by the manufacturer to
provide a useful service life. If a relay is operated above its rating, it will
not
immediately self destruct, but its life will be shortened. If a relay is already
energized when a short circuit occurs, a relay could carry 2 or 3 times its rated
current for a short time, long enough for an ANL fuse to blow.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494971#494971
Message 3
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| Subject: | Re: New role for the E-Bus? |
>
>I'm not following the 'FAR 23' issue with relays at the engine bus
>for downstream stuff.
>A fuse at the bus protects everything downstream of the fuse.
The 'issue' concerns maximum circuit
protection for always hot feeders. Classically,
the FAA has holy watered 5A as a maximum.
Which doesn't make much sense to me . . .
There's a huge difference in energy released
in a short wire downstream of fuses versus
breakers and 14v vs. 28v.
The legacy backstop was to add disconnect
at the battery . . . relay, contactor etc.
>When I did failure analysis for my single battery/dual alt,
>electrically dependent alternative engine, it looked like any
>conventional arrangement of dual alts with control fed by the main
>bus and B leads *to* the main bus, would result in the loss of both
>alts if the master is turned off ('smoke in the cockpit'). I chose
>to route one alt's B lead directly to the engine bus, making it
>effectively a dedicated electrical power source for the engine,
>controlled via the engine bus. Goal was to preserve 'classical'
>engine independence, and not depend on the limited energy in the
>battery to complete the flight. There is still a cross-tie switch
>between engine and main buses, to maintain alt failure redundancy.
>Is there a problem with this approach?
Don't think so . . . but schematics speak
far more clearly than words. Could you sketch
your architecture and scan or photograph it
for sharing?
Sorry for the delay. Got a 'bug' last Friday
night and I'm just now getting up and around. . .
Bob . . .
Message 4
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| Subject: | Re: New role for the E-Bus? |
On 2/24/2020 7:00 PM, Robert L. Nuckolls, III wrote:
>>
>> I'm not following the 'FAR 23' issue with relays at the engine bus
>> for downstream stuff.
>> A fuse at the bus protects everything downstream of the fuse.
>
> The 'issue' concerns maximum circuit
> protection for always hot feeders. Classically,
> the FAA has holy watered 5A as a maximum.
> Which doesn't make much sense to me . . .
> There's a huge difference in energy released
> in a short wire downstream of fuses versus
> breakers and 14v vs. 28v.
>
> The legacy backstop was to add disconnect
> at the battery . . . relay, contactor etc.
>
>> When I did failure analysis for my single battery/dual alt,
>> electrically dependent alternative engine, it looked like any
>> conventional arrangement of dual alts with control fed by the main
>> bus and B leads *to* the main bus, would result in the loss of both
>> alts if the master is turned off ('smoke in the cockpit'). I chose to
>> route one alt's B lead directly to the engine bus, making it
>> effectively a dedicated electrical power source for the engine,
>> controlled via the engine bus. Goal was to preserve 'classical'
>> engine independence, and not depend on the limited energy in the
>> battery to complete the flight. There is still a cross-tie switch
>> between engine and main buses, to maintain alt failure redundancy. Is
>> there a problem with this approach?
>
> Don't think so . . . but schematics speak
> far more clearly than words. Could you sketch
> your architecture and scan or photograph it
> for sharing?
>
> Sorry for the delay. Got a 'bug' last Friday
> night and I'm just now getting up and around. . .
>
>
> Bob . . .
>
Hi Bob,
RE: the FAR23 issue, I was referring to a drawing posted earlier that
had multiple relays fed from a bus which itself was already controlled.
Most of the loads could have been handled easily by switches.
To separating the alternator feed-in locations:
Is my thinking incorrect about having both alternators controlled by and
fed to the main bus? It seems that shutting off the master would also
shut off both alternators. To solve that....
Attached is my MS Paint-abused rough draft, using cut/paste from an
Aeroelectric drawing.
Both alts are internally regulated in this drawing (yeah, I know that
you're not a fan, but it's ~$150 vs ~$1000, and I won't be randomly
flipping alt switches in flight).
All engine related components, and one alternator, are fed
from/controlled by the (badly labeled) 'Main Battery Bus (Engine)'. The
correct name would be simply 'Engine Bus'.
Everything else, including the other alternator, is fed by the Main bus.
As I said, this is very rough; any labels beyond the basic battery,
buses, alternators, and switching are 'artifacts' of the cannibalized
original drawing.
Charlie
Message 5
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| Subject: | Re: Power Duece Schottky diodes |
rv8iator wrote:
> Beware of counterfeit semiconductorson EBay...
>
> https://www.electro-tech-online.com/blog-entries/watch-out-for-counterfeit-transistors.78 (https://www.electro-tech-online.com/blog-entries/watch-out-for-counterfeit-transistors.78)
>
>
> I purchased some 2N3055 power bipolors. cut them open and they were counterfeit.
Tiny die compared to the original STMicro parts. This may be the case when
you see bargain low ball prices for other semiconductors. The modus operandi
seems to be to re label parts that look identical to the original but are of lower
power higher noise spec.
>
>
>
> Chris
> RV-8 twice
>
>
>
>
> On Sat, Feb 22, 2020 at 10:17 AM Charlie England wrote:
>
>
> >
> >
> >
> >
> > On Sat, Feb 22, 2020 at 11:14 AM Randy C-GRPY wrote:
> >
> >
> > >
> > > I want dual diodes to feed alternate power to critical components with only
one power input. The ones sold by Perihelion Designs seem to fit the bill
well but are quite pricey. Are they worth the cost or are there equally good,
cheaper solutions to be considered?
> > >
> > > Thanks
> > > Randy
> > >
> > >
> >
> >
> > There are hundreds of choices on ebay, at prices all over the map (even for
the same device). ex: The stps12045tv is a dual 60A 45V device with an electrically
isolated base (simpler mounting) that can be found for as much as $75,
or as little as 2 for $12, if you're willing to wait a few weeks for them to arrive
from China. Mouser (major electronics supplier) has them for $20. If you
spend more time searching, you might find some even cheaper; I did several months
ago.
> >
> >
> > If you don't need that much current, you can get a whole bag of them for less
than $10 in some cases. Do exercise caution when mounting any metal tabbed
device, to be sure the tab isn't electrically common to one of the leads. When
browsing, just look for voltage above ~20V, at whatever current you need. Remember
that current ratings assume significant heat sinking; if you want to avoid
mounting on a heat sink, just oversize the device significantly for the job.
A legit heat sink will probably cost a lot more than upsizing the device. :-)
> > https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=dual+schottky+diode&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=stps12045tv (https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=dual+schottky+diode&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=stps12045tv)
> >
> >
> >
> >
> >
> >
> >
>
Thanks for the heads up. I think I will stick to Digikey, Mouser, or Newark. Im
thinking they dont buy from unknown suppliers.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494985#494985
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