Today's Message Index:
----------------------
1. 06:27 AM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III)
2. 07:11 AM - Re: Use of non-aviation Ford-style regulators (Robert L. Nuckolls, III)
3. 09:22 AM - Relay protection diodes. (Victor Menkal)
4. 09:22 AM - Re: Re: Auto Aux Fuel Pump Circuit Idea (Robert L. Nuckolls, III)
5. 10:42 AM - Re: Purpose of Diodes on Relays (rayj)
6. 11:22 AM - Vans 35A alternator - Nippondenso 14184 (Peter Mather)
7. 11:31 AM - Re: Purpose of Diodes on Relays (Noel Loveys)
8. 01:32 PM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III)
9. 01:43 PM - Re: Auto Aux Fuel Pump Circuit Idea (Fred Stucklen)
10. 01:49 PM - Re: Vans 35A alternator - Nippondenso 14184 (Robert L. Nuckolls, III)
11. 02:02 PM - Re: Purpose of Diodes on Relays (Robert L. Nuckolls, III)
12. 02:52 PM - Re: Vans 35A alternator - Nippondenso 14184 (Peter Mather)
Message 1
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Subject: | Re: Purpose of Diodes on Relays |
At 11:26 PM 12/15/2011, you wrote:
I noted that the manufacturer of my ignition switch requests a diode
across the between the excitation (low current start switch) input
and ground. Also noted that Bob calls out diodes on fig Z-16
wiring diagram for the Rotax 912. Can anyone provide a simple
explanation of reason for these? As well Bob did not call out the
diode on Z-16 but assume its the same as the other drawings which
calls for a 1N5400 diode.
Capacitors and inductors are both capable of 'storing
energy'. Capacitors store charge as a voltage which
manifests when electrons pile up in the insulating
space between two conductors. Discharging a capacitor
offers potential for a very high current event.
Inductors store a charge in their magnetic fields.
While current is flowing from external sources, a
field is generated within the core of the inductor.
When that external source is removed, the magnetic
field collapses rapidly. Voltage generated in the
windings of the inductor is proportional to the number
of turns, strength of the field and RATE OF CHANGE
for the collapse of that field.
The diodes shown wired in parallel with the coils
of relays and solenoids to effect an orderly management
of that stored energy. See . . .
http://www.aeroelectric.com/articles/spikecatcher.pdf
We've had some past discussions here on the List
about the 'optimal' choice of components for managing
this energy. The confusion has been compounded by
erroneous notions published over the signatures of
people who should have known better. Suffice it to
say that for OUR purposes in the crafting systems
with exceedingly low service cycles . . . the plain
vanilla diode approach illustrated in my drawings
suffices nicely.
Here's a capture of one such discussion thread where
I attempted to apply some simple-ideas in physics
with practical recipes for success in the art
of 'spike management' . . .
http://www.aeroelectric.com/articles/spike.pdf
Know also that good management of this energy does
NOT go to the PROTECTION of solid state devices in
the ship's systems. It's for protection of service
life on the controlling device. I.e., diode on the
battery contactor improves on the service life of
the battery master switch. Suppression of this transient
also goes to minimizing the probability of interference
with other systems . . . which is a transient
performance event, not a destructive event.
ANY diode is capable of doing the job electrically.
I recommend the 1N5400 series devices for their
robust MECHANICAL qualities. But the actual
part number is electrically non-critical.
I really like Bob's crow bar over voltage module and alternator
disconnect relay which is not included in the standard Rotax wiring
schematic. Low cost and easy to install (following Bob's schematic
of course) and covers off one problem area which a number of Rotax
owners have identified with the standard wiring system and
rectifier. Best part is that my ALT switch on the panel is now
gainfully employed (not used following standard Rotax
diagram). Over voltage protection option is also highly
recommended by the Rotax guru's at Rotec Research Canada.
I have not been made aware of any runaway alternator
situations with the PM alternators. A rectifier/regulator
is: (1) an electrical device that HAS runaway failure
modes and(2) is highly stressed - runs hotter than !@#$@#.
OV protection seems a prudent addition to the stock
drawings supplied by engine manufacturers which never
seem to include OV protection recommendations.
We theorized here on the List that the public relations
types for the various engine suppliers would be
embarrassed to admit that their product offering could
fail in a very unhappy manner. Hence, "let us not
admit it by recommending ov protection."
Bob . . .
Message 2
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Subject: | Re: Use of non-aviation Ford-style regulators |
Paul Millner wrote:
Note that it can be dangerous to use non-aviation Ford-type
regulators in our airplanes. When the alternator half of the master
switch is turned off, the regulator will allow the alternator to go
into a voltage runaway mode, and that overvoltage will not be
controlled by your overvoltage relay (since the field current is
flowing via a separate path, directly from the alternator). The
overvoltage condition can cook your avionics and battery.
Even if you don't turn off the alternator half of the master switch,
if your separate overvoltage relay trip for any reason with such a
regulator installed, that, ironically, will trigger the voltage
runaway scenario.
Paul
At 07:02 PM 12/15/2011, you wrote:
Uh oh. What's the protection for this? I'm using not a Ford, but a
smaller, denser, lighter Japanese alternator with same output.
David Merchant
Man! I've not had occasion to lift the lid on this
pot of stew since I owned the Benton Airpark (1K1)
22 years ago.
Paul's admonition arises from the fact that SOME
solid state replacements for the original Ford
electromechanical regulators do not conform to the
form, fit and function of those regulators. As installed
first on automobiles the Ford style regulator was
configured thusly:
Emacs!
The regulator contained two "relay" like devices wherein
one relay was the voltage regulator and the second was
used as an ON-OFF control of field excitation. The
field relay sensed a DC voltage on the alternator's
"N" terminal (y-wound stator center tap) and would
automatically excite an alternator as soon as the
engine was started and the alternator was demonstrated
to be in motion. This all happened through a tiny
excitation current that would flow through the
alternator warning light bulb into the regulator's
"I" or indicator terminal.
Failure of this light bulb led to a lot of regulators
and alternators being swapped out as mechanics who
did not understand the system tried to get their
customer's car back on the road. Later systems
added a resistor across the lamp to make sure that
the alternator would still come on line even if the
bulb were burned out. This is the root-system from
which Cessna's alternators evolved.
Cessna chose to run their field supply voltage right
into the "A" terminal and control the field supply
relay directly with alternator field switch controlling
the "S" terminal. In later years, the OV protection
module (first proposed by yours truly) was inserted
between the alternator field switch and the "S" terminal.
Emacs!
So much for the history. In later years, solid state
replacements with the same A, S, I and F terminal
markings were crafted where the S-terminal was no
longer used for field control but for BUS VOLTAGE
SENSING. When one drops one of these regulators into
an automobile, the system still performs in a useful
manner. When dropped into a Cessna, opening the field
control side of the split master switch deprived the
regulator of control information causing the alternator
to full-field . . . i.e. OV runaway.
I'm not sure that ALL solid state drop-ins for a
Ford regulator behave in this manner . . . but some
do. Been there, done that on one of my rental fleet
airplanes. But if "Ford-style" regulators are wired
per recommendations in the Z-figures (A and S terminals
tied together) there is no risk for experiencing the
design induced runaway condition.
Bob . . .
Message 3
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Subject: | Relay protection diodes. |
Thanx David. I think I found the reason for the diodes is to protect electronics
from the brief high voltage spike created in the relay coils when the relay
is switched off. Appreciate advice if a 1N5400 diode (3A 100V) is ok for
the master relay.
Thanx Vic
Vic Menkal
CH750 Rotax 912ULS
Whitehorse Yukon
Message 4
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Subject: | Re: Auto Aux Fuel Pump Circuit Idea |
At 09:59 PM 12/15/2011, you wrote:
><fred.stucklen@utcfuelcells.com>
>
>I've given some more thought and testing on the Auto Aux Fuel Pump
>idea that I originally posted. I've attached a schematic of a
>circuit I've bread boarded and tested. Seems to to work.
> The idea/implementation is to automatically turn the pump ON for
> as long as the fuel pressure is below a set limit, and don't turn
> it off until the pressure has been above that limit for at least 10
> seconds. If the pressure go low again, the process is repeated.
> I'm planning on making up a hardwired proto board and actually
> testing in my RV-7A, but probably not until after the new year.....
The circuit yields well to critical review but it took
me a bit of feather-sorting to understand application
of the power FET as drawn. You your schematic has the
bulk connection tied to the drain terminal and the
thing that jumped off the page at me was an N-channel
FET. But after sorting out the S-G-D labels and
application in the circuit, the real P-channel
device emerged.
Another approach worth considering is use of an N-Channel
device as a pull-down switch. You'd need to do some re-wiring
to make the pump's manual ops be pull-to-ground too.
The N-channel offers potentially 1/10th the on-resistance
of a P-channel. Heat sinking of the device becomes much
easier and performance goes up with the reduced voltage
drop.
Bob . . .
Message 5
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Subject: | Re: Purpose of Diodes on Relays |
On 12/16/2011 08:23 AM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> Capacitors and inductors are both capable of 'storing
> energy'. Capacitors store charge as a voltage which
> manifests when electrons pile up in the insulating
> space between two conductors. Discharging a capacitor
> offers potential for a very high current event.
Greetings,
It's my understanding that the electrons accumulate in the conductor on
one side of the insulating space while "holes" accumulate in the
conductor on the other side of the insulating space.
Clarification?
Raymond Julian
Kettle River, MN
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine
>
> Inductors store a charge in their magnetic fields.
> While current is flowing from external sources, a
> field is generated within the core of the inductor.
> When that external source is removed, the magnetic
> field collapses rapidly. Voltage generated in the
> windings of the inductor is proportional to the number
> of turns, strength of the field and RATE OF CHANGE
> for the collapse of that field.
>
> The diodes shown wired in parallel with the coils
> of relays and solenoids to effect an orderly management
> of that stored energy. See . . .
>
> http://www.aeroelectric.com/articles/spikecatcher.pdf
>
> We've had some past discussions here on the List
> about the 'optimal' choice of components for managing
> this energy. The confusion has been compounded by
> erroneous notions published over the signatures of
> people who should have known better. Suffice it to
> say that for OUR purposes in the crafting systems
> with exceedingly low service cycles . . . the plain
> vanilla diode approach illustrated in my drawings
> suffices nicely.
>
> Here's a capture of one such discussion thread where
> I attempted to apply some simple-ideas in physics
> with practical recipes for success in the art
> of 'spike management' . . .
>
> http://www.aeroelectric.com/articles/spike.pdf
>
> Know also that good management of this energy does
> NOT go to the PROTECTION of solid state devices in
> the ship's systems. It's for protection of service
> life on the controlling device. I.e., diode on the
> battery contactor improves on the service life of
> the battery master switch. Suppression of this transient
> also goes to minimizing the probability of interference
> with other systems . . . which is a transient
> performance event, not a destructive event.
>
> ANY diode is capable of doing the job electrically.
> I recommend the 1N5400 series devices for their
> robust MECHANICAL qualities. But the actual
> part number is electrically non-critical.
>
> I really like Bob's crow bar over voltage module and alternator
> disconnect relay which is not included in the standard Rotax wiring
> schematic. Low cost and easy to install (following Bob's schematic of
> course) and covers off one problem area which a number of Rotax owners
> have identified with the standard wiring system and rectifier. Best part
> is that my ALT switch on the panel is now gainfully employed (not used
> following standard Rotax diagram). Over voltage protection option is
> also highly recommended by the Rotax guru's at Rotec Research Canada.
>
> I have not been made aware of any runaway alternator
> situations with the PM alternators. A rectifier/regulator
> is: (1) an electrical device that HAS runaway failure
> modes and(2) is highly stressed - runs hotter than !@#$@#.
> OV protection seems a prudent addition to the stock
> drawings supplied by engine manufacturers which never
> seem to include OV protection recommendations.
>
> We theorized here on the List that the public relations
> types for the various engine suppliers would be
> embarrassed to admit that their product offering could
> fail in a very unhappy manner. Hence, "let us not
> admit it by recommending ov protection."
>
>
> Bob . . .
>
>
Message 6
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Subject: | Vans 35A alternator - Nippondenso 14184 |
Can anyone tell me the purpose of the third wire on the connector of this
alternator?
The cable supplied by Vans has Black - ground; green - field; white - not
connected.
I'm looking at using a regulator that has a stator connection which it uses
to drive an ignition light - is the white connection to the stator?
Thanks in advance
Peter
Message 7
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Subject: | Purpose of Diodes on Relays |
A starting motor is essentially a coil. When you activate the starter (read
coil) draws down on the current of the battery. The more load on the
starter the greater the current drawn by the starter. When you release the
starter button, key or whatever, all the energy stored up in the coil (or
starter motor) is immediately dumped into the circuit, with extremely high
voltage in reverse polarity. The diode allows this reverse potential to be
drained off safely without frying all your expen$ive avionics and other
digital equipment on the buss.
Clear as mud?
Noel
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Victor
Menkal
Sent: December 16, 2011 1:56 AM
Subject: AeroElectric-List: Purpose of Diodes on Relays
I noted that the manufacturer of my ignition switch requests a diode across
the between the excitation (low current start switch) input and ground.
Also noted that Bob calls out diodes on fig Z-16 wiring diagram for the
Rotax 912. Can anyone provide a simple explanation of reason for these?
As well Bob did not call out the diode on Z-16 but assume its the same as
the other drawings which calls for a 1N5400 diode.
I really like Bob's crow bar over voltage module and alternator disconnect
relay which is not included in the standard Rotax wiring schematic. Low
cost and easy to install (following Bob's schematic of course) and covers
off one problem area which a number of Rotax owners have identified with the
standard wiring system and rectifier. Best part is that my ALT switch on
the panel is now gainfully employed (not used following standard Rotax
diagram). Over voltage protection option is also highly recommended by
the Rotax guru's at Rotec Research Canada.
Thanx Vic
CH750 Rotax 912ULS-2
Whitehorse Yukon
Message 8
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Subject: | Re: Purpose of Diodes on Relays |
>
>Greetings,
>
>It's my understanding that the electrons accumulate in the conductor
>on one side of the insulating space while "holes" accumulate in the
>conductor on the other side of the insulating space.
>
>Clarification?
That's a good a analogy. Here are some
explanations with a lot of mathematical
description but one can clean the simple-ideas
of the physics . . .
http://en.wikipedia.org/wiki/Dielectric
http://www.physics.sjsu.edu/becker/physics51/capacitors.htm
Bob . . .
Message 9
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Subject: | Re: Auto Aux Fuel Pump Circuit Idea |
nuckolls.bob(at)aeroelect wrote:
> At 09:59 PM 12/15/2011, you wrote:
>
> Bob,
>
> Yep, I guess I drew the MOSFET incorrectly. It is a "P" channel device. Power
dissipation on this .02 ohm ON device should be minimal. So far testing has
show that it can draw 10 amps with no heatsink.... I will heatsink it in the
prototype.
> I'd rather test the concept in a way that involves little change to the existing
wiring in the plane. I currently have the circuit wired to switch the positive
side, so the "P" Channel device works better for me. Very easy to change
it to a pull down circuit if some one else wanted that method.
> I think the next step is to prototype it, bench check it using an actual pump
(instead of the halogen bulb I'm currently using for a load)and then begin
actual flight testing of the timed concept. If this works out OK, it might be
lower cost to implement the design using the PIC processor.
> By the way, thanks for the proto board idea. I might use that in the future...
>
> Fred Stucklen
> RV-7A N924RV 650 Hrs
>
>
>
The circuit yields well to critical review but it took
me a bit of feather-sorting to understand application
of the power FET as drawn. You your schematic has the
bulk connection tied to the drain terminal and the
thing that jumped off the page at me was an N-channel
FET. But after sorting out the S-G-D labels and
application in the circuit, the real P-channel
device emerged.
Another approach worth considering is use of an N-Channel
device as a pull-down switch. You'd need to do some re-wiring
to make the pump's manual ops be pull-to-ground too.
The N-channel offers potentially 1/10th the on-resistance
of a P-channel. Heat sinking of the device becomes much
easier and performance goes up with the reduced voltage
drop.
Bob . . .[/quote]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=361068#361068
Message 10
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Subject: | Re: Vans 35A alternator - Nippondenso 14184 |
At 01:17 PM 12/16/2011, you wrote:
>
>Can anyone tell me the purpose of the third wire on the connector of this
>alternator?
>
>The cable supplied by Vans has Black - ground; green - field; white - not
>connected.
>
>I'm looking at using a regulator that has a stator connection which it uses
>to drive an ignition light - is the white connection to the stator?
Does Van's alternator REQUIRE an external
regulator? Last time I looked, their offerings
were internally regulated. Can you post an excerpt
of the schematic . . . or point us to a link where
your applicable schematic is visible?
Trying to give useful advise based on numbers of
pins and colors of wires is risky. The SCHEMATICS
associated with the products being explored are
necessary for offering well considered advice.
Bob . . .
Message 11
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Subject: | Purpose of Diodes on Relays |
At 01:28 PM 12/16/2011, you wrote:
>A starting motor is essentially a coil. When you activate the
>starter (read coil) draws down on the current of the battery. The
>more load on the starter the greater the current drawn by the
>starter. When you release the starter button, key or whatever, all
>the energy stored up in the coil (or starter motor) is immediately
>dumped into the circuit, with extremely high voltage in reverse
>polarity. The diode allows this reverse potential to be drained off
>safely without frying all your expen$ive avionics and other digital
>equipment on the buss.
A few years back (about 11) when we were
exploring the behavior of energy stored on
inductive devices, we discovered (and demonstrated
on the bench) that un-suppressed spikes from
inductive devices are almost totally dissipated
across the spreading contacts of the switching
device. For example, here's one of many plots
we gathered while stirring the Contactor-Spike-
Stew pot:
http://www.aeroelectric.com/Pictures/Curves/CH_Bus_Noise_w_0p1_Cap.gif
There are two traces. The top one shows voltage
developed across the contacts of the controlling
switch . . . the lower trace shows voltage that
made it out to the bus . . . barely perceptible.
Know that electronic devices designed to run directly
from the bus of any vehicular DC system is (1) easily
designed to stand off the (2) minuscule packet of
energy that makes it across the opening switch.
In short, there is no risk of "frying" anything. The
major risk is shortened service life of the switch
that controls the contactor.
The same conditions apply to energy dumped from
a starter motor . . . it's the starter contactor
that takes the hit, not electro whizzies running
off the bus. One might think that an inductor
charged to hundreds of amps represents the grand
dragon of spike generators. Motors have a unique
feature called counter-emf. A 12v motor really runs
on the DIFFERENCE voltage between applied voltage
(battery) and counter-emf due to rotation. The
real free inductance model of a motor is rather
small in comparison with contactor coils having
hundreds of turns of wire. This is why you never
see spike suppressors on a motor . . . they're
just not a potential threat.
Bob . . .
Message 12
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Subject: | Vans 35A alternator - Nippondenso 14184 |
Bob
The alternator is one Vans were selling back in 04. It is externally
regulated and Vans then recommended a VR-1751 or MS-150A regulator but
always said to leave the white lead "unconnected"
I can't see what else the third wire could be except a stator connection but
any suggestions or test ideas would be appreciated.
Best Regards
Peter
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: 16 December 2011 21:42
Subject: Re: AeroElectric-List: Vans 35A alternator - Nippondenso 14184
--> <nuckolls.bob@aeroelectric.com>
At 01:17 PM 12/16/2011, you wrote:
>--> <peter@mather.com>
>
>Can anyone tell me the purpose of the third wire on the connector of
>this alternator?
>
>The cable supplied by Vans has Black - ground; green - field; white -
>not connected.
>
>I'm looking at using a regulator that has a stator connection which it
>uses to drive an ignition light - is the white connection to the stator?
Does Van's alternator REQUIRE an external
regulator? Last time I looked, their offerings
were internally regulated. Can you post an excerpt
of the schematic . . . or point us to a link where
your applicable schematic is visible?
Trying to give useful advise based on numbers of
pins and colors of wires is risky. The SCHEMATICS
associated with the products being explored are
necessary for offering well considered advice.
Bob . . .
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