Today's Message Index:
----------------------
1. 10:37 AM - Re: Re: OVM14 MkIII, rev P1 (Robert L. Nuckolls, III)
2. 10:50 AM - Re: Re: OVM-14 MkIII (Robert L. Nuckolls, III)
3. 11:14 AM - Radio Noise (Jeff Luckey)
4. 12:29 PM - Re: OVM14 MkIII, rev P1 (user9253)
5. 12:40 PM - Hall as current sensors (Finn Lassen)
6. 12:49 PM - Re: Radio Noise (Finn Lassen)
7. 01:31 PM - Re: Re: OVM14 MkIII, rev P1 (Jeff Luckey)
8. 01:31 PM - Re: Re: OVM14 MkIII, rev P1 (M Wilson)
9. 01:41 PM - Re: Re: OVM14 MkIII, rev P1 (Robert L. Nuckolls, III)
10. 01:46 PM - Re: Radio Noise (Robert L. Nuckolls, III)
11. 03:24 PM - Re: OVM14 MkIII, rev P1 (Eric Page)
12. 04:02 PM - Re: OVM14 MkIII, rev P1 (Eric Page)
Message 1
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| Subject: | Re: OVM14 MkIII, rev P1 |
At 09:37 PM 9/24/2023, you wrote:
>
>If the overvoltage module ground wire is connected to ground using a
>screw in an easily accessible location,
>then it would be fairly easy to test the OVM using 3 "D" cell
>batteries in series per this thread:
>http://forums.matronics.com/viewtopic.php?p=480365
>The advantage of this method is that every component of the OVM is
>tested including all resistors and the LM431.
You are correct . . . I published a similar technique
in the CBOVM DIY project
http://aeroelectric.com/AEC_Legacy_Products/9003/DIY_Crowbar_OVP_F.pdf
The proposed 'jiggering' of the ov trip setpoint
resistors also confirms full functionality of all
components along with a rough but reassuring
validation of calibration.
Normal ops centers the design point trip value
of, in this case, 16.0 Volts. Adding the little
tug on this setting via the testing circuit
centers the trip at what is an accepted
value for low voltage warning . . . 13.5
Volts.
This is a value at which the battery neither
takes on more energy (charges) nor does it
significantly deliver energy (discharge).
Test voltages above and below this value
are readily provided by temporary operation
of ship's power with alternator ON (14.2
or higher) and alternator OFF (12.8 or lower).
The marketing goal for the test feature is
to encourage owner/operators to periodically
verify functionality of the ov management
system. We KNOW how easy it is to allow some
critical feature of our machines to languish
especially when 'things have been running
along nicely for a long time'.
Batteries are a good example. Timing belts
on engines are another. Here on the List we
once studied a constellation of what I
called 'dark-n-stormy-night' stories published
in aviation rags. In EVERY story related
by someone who survived a bad time in the
cockpit, the after-action follow up never
spoke of poor preventative maintenance,
lack of planning or pilot ignorance as to
the condition of the equipment he/she was
flying.
Of course, those who did not survive similar
events were unable to favor us with an
"I learned about flying from that" story.
The crowbar ov module was produced for decades
by both AEC and B&C. AEC warranty on products
is LIFETIME.
https://matronics.com/aeroelectric/Catalog/warranty.html
Over the lifetime of CB OVM module production
I've had two returns. Both modules were toast.
Seems they were mis-installed with the wrong
upstream circuit protection. In neither case
did the customer cite damage to the rest of
the airplane. Both modules were replace along
with my thanks for the field-service feedback.
OV events are rare but not zero. The probability
of any particular OV module failing to rise
to duty is also very small but (it's
a manufactured device) NOT zero. It seems
a good idea to offer some simple, minimal
effort feature that tends to drive that risk
toward zero.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Re: OVM-14 MkIII |
> Due to the nature of LR3 crowbar ov protection,
> an OV event is followed milliseconds later
> by a LV event. There would not be any time
> to sense, display and perceive an OV condition.
>
>
>That behavior I /do/ remember, from years of you
>repeating it (so that we dullards might learn
>it).=C2 And that=99s what spurred my comment '
>the way I understood the OV event in a Z-figure
>environment, OV would occur and be terminated
>before the lamp could heat up; the chances of
>pilot notice are exceedingly small.=C2 Other
>annunciations would be necessary to indicate
>that an OV event preceded the LV condition.
>
>Neal
Exactly so my friend. Having been both designer
and producer of ov management components in both TC
and experimental markets for decades there was only ONE
device conceived that featured both OV and LV
warning. I designed it for B&C in response to
some demand from the ultralight community. Seems
it is still offered.
https://bandc.com/product/over-under-voltage-sensor/
In this instance, potential for a runaway
alternator to quickly drive bus voltage to
dangerous heights was small . . the alternator
would struggle for some time to push the battery
above 16.0v
Further, these airplanes almost never had
panel mounted, bus drive avionics . . . radios
were hand-held. I wonder how many of these
got installed on more complex airplanes . . .
not a problem. But if the alternator is
judiciously configured, the OV warning
light would never be noticed.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=======
=
< Go ahead, make my day . . . >
< show me where I'm wrong. >
========================
========
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 3
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Seeking with wisdom of the Collective.
I'm hearing an intermittent "crackle" in the audio of an ICOM com radio but
only when engine is running.=C2- It is not ignition noise.=C2- I know
this because when I turn-off the squelch, I can hear the Ignition "ripple"
in the background.=C2- This "crackle" is a different sound.=C2- (sorry,
it's hard to describe sounds with words)
Environment:Older ICOM A200 Com radio
There is a Dynon intercom in the system.Old Narco transponder
2-place airplane, headsets only, no speakerIO-360 with conventional mags
Symptoms:1. A loud short-duration "crackle" occurs randomly every 3 to 10 s
econds accompanied by a RECEIVE indication on the face of the radio.2. Only
happens when engine is running3. This "crackle" is breaking squelch
My first guess was a loose connection in the antenna circuit.=C2- I have
checked the antenna connection at the antenna and it appears to be OK.=C2
- The coax is split-out and soldered to the antenna.=C2- The solder con
nection looks good and nothing is loose at the antenna.
The radio is very difficult to get to.=C2- The airplane seems to have bee
n "built around" the avionics.=C2-=C2-
I'm trying to check the easy stuff first before tearing-up the air frame to
gain access to the radio.
Suggestions?
Cheers,
-Jeff
Message 4
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| Subject: | Re: OVM14 MkIII, rev P1 |
There is more than one way to test the OVM. Most people would prefer a simple
push button test.
A perfectionist might want to go to the trouble of testing the complete circuit
with actual voltage that is too high.
Some people want an indicator light to tell if the OVM tripped the alternator field
breaker, thus saving troubleshooting time.
Maybe there is way to accomplish that using solid state components instead of a
latching relay.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511490#511490
Message 5
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| Subject: | Hall as current sensors |
After reading the /Hall of fame/ article by Jim Weir in the July 2019
/Kitplanes/ magazine I purchased the T50-26 ferrite toroids and
drv5053VA Hall effect sensors and put the notched toroids on cables
to/from battery before I crimped and soldered the terminals.
This month I finally got around to making the sensors and an amplifier
board for then (going to analog inputs of an Arduino Mega 2590 with data
logging on SDRAM card and 4x20 character display). Attached my schematic
of amplifiers. (Not shown the hall sensors with 22nF across power and
ground fed by the Mega 2590's 5V power output.)
Datasheet https://www.ti.com/lit/ds/symlink/drv5053.pdf shows that the
zero current output from them can vary between 0.9V to 1.15V, thus the
need for the potentiometers for zero adjustment. The max output range is
0.81V before saturation with typical -90mV/mTesla and saturation of 9mT.
On the bench with about 10 amps thru the toroids I got from 12 to 19 mV
per amp with the four different sensors in the toroids.
Note that the LM324 opamps max output is supply - 1.5V (3.5V in my case).
I wanted four sensors: Engine bus, Main bus, Alternator output and
Starter. However, looking at the datasheet for the drv5053VA sensor it
was obvious it would be overloaded (saturated) at starter currents, so I
decided to use the forth sensor for Alternator field current.
I wanted about 20A max range for Engine and Main buses, 40 - 50 amps
(hall sensor saturation) for alternator output and about 7 to 10 amps
for alternator field. Using resistors I had on hand I arrived at these
amplification factors:
Engine bus: 7.5x
Main bus: 6.8x
Alternator out: 4.7x
Alternator field: 33x
In theory this should all have worked fine. Install the sensors and
amplifier board, zero out each amplifier with no currents running. Then
run about 10 to 12 amps (1 ohm 120W resistor) with a 0.020 ohm 1%
resistor in series and measure voltage across that to get actual current
(didn't know tolerance of 1 ohm resistor). Compare voltage with
displayed voltage on Arduino display and program correction factors for
each of the four channels (sensors).
Worked fine with the Alternator field current sensor (installed further
from other sensors).
However, when I turned on current to alternator field (engine not
running) the engine bus and alternator out current displays jumped from
zero!
Penny finally dropped that the alternator magnetic field is way too
close to the current sensors as installed. I should have realized that
when I had trouble adjusting the Alternator out to zero (that sensor is
mounted just a few inches from the alternator).
So that is the purpose of this thread: to warn anybody that might use
this method to measure currents that the sensors are sensitive to
surrounding magnetic fields, permanent and varying (like the alternator
field).
Obvious solution would be to move the sensors to locations further from
magnetic fields. But in my case that would require removing and
reinstalling crimped and soldered ring terminals on the cables. And for
the Alternator out I would have to add a significant length of wire
between alternator and the battery to get that sensor away from the
alternator. So much for my elegant short wire between alternator and
battery :(
Perhaps a better solution in my case (at least for the engine and main
bus) is to measure the voltages over the 3 - 4 feet long 10AWG cables
from battery to fuse panels using the opamps as differential amps. 10V
zeners from each end of cables to inverting and non-inverting inputs
respectively. Still need to figure out exact schematic and values.
But, again, beware using Hall effect current sensors near external
magnetic fields.
Finn
Message 6
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Do you have strobes installed and on when you hear that?
Independent of engine RPM (vibrations)?
Finn
On 9/25/2023 2:13 PM, Jeff Luckey wrote:
> Seeking with wisdom of the Collective.
>
> I'm hearing an intermittent "crackle" in the audio of an ICOM com
> radio but only when engine is running. It is not ignition noise. I
> know this because when I turn-off the squelch, I can hear the Ignition
> "ripple" in the background. This "crackle" is a different sound.
> (sorry, it's hard to describe sounds with words)
>
> Environment:
> Older ICOM A200 Com radio
> There is a Dynon intercom in the system.
> Old Narco transponder
> 2-place airplane, headsets only, no speaker
> IO-360 with conventional mags
>
>
> Symptoms:
> 1. A loud short-duration "crackle" occurs randomly every 3 to 10
> seconds accompanied by a RECEIVE indication on the face of the radio.
> 2. Only happens when engine is running
> 3. This "crackle" is breaking squelch
>
> My first guess was a loose connection in the antenna circuit. I have
> checked the antenna connection at the antenna and it appears to be
> OK. The coax is split-out and soldered to the antenna. The solder
> connection looks good and nothing is loose at the antenna.
>
> The radio is very difficult to get to. The airplane seems to have
> been "built around" the avionics.
>
> I'm trying to check the easy stuff first before tearing-up the air
> frame to gain access to the radio.
>
> Suggestions?
>
>
> Cheers,
>
> -Jeff
>
Message 7
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| Subject: | Re: OVM14 MkIII, rev P1 |
Joe,
You wrote:
"Maybe there is way to accomplish that using solid state components instead
of a latching relay."
There definitely is, however the latching relay has a few advantages over l
ogic circuit latch:=C2-
1. it's cheap (~$2)
2. simple circuitry
3. relays are bullet proof (very tolerant of "noisy" environments)
-Jeff
On Monday, September 25, 2023 at 12:35:22 PM PDT, user9253 <fransew@gma
il.com> wrote:
There is more than one way to test the OVM.=C2- Most people would prefer
a simple push button test.
A perfectionist might want to go to the trouble of testing the complete cir
cuit with actual voltage that is too high.
Some people want an indicator light to tell if the OVM tripped the alternat
or field breaker, thus saving troubleshooting time.
Maybe there is way to accomplish that using solid state components instead
of a latching relay.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511490#511490
-
S -
WIKI -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 8
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| Subject: | Re: OVM14 MkIII, rev P1 |
If you really want an OV indicator it is easy to do.=C2- I think this wa
s shown already.=C2- Just connect an LED fed by a separate source of 12 v
olts and a 270 ohm 1/2W resistor to the RED20 terminal of the OVM.=C2- Wh
en the SCR trips and the breaker opens the LED will light and it's current
will keep the SCR tripped - latching.=C2- The data sheet for the BT139-60
0E specifies a 45mA hold current, so the LED and resistor should be sized t
o supply that much current.=C2- But, the typical hold current is 4mA, so
you can probably get by with a larger resistor and smaller LED.This LED:=C2
-=C2-Dialight 5596101027F=C2-=C2-can handle 50mA.=C2- I would pro
bably start with a 470 ohm resistor instead of 270 ohm.
On Monday, September 25, 2023 at 02:38:51 PM CDT, user9253 <fransew@gma
il.com> wrote:
There is more than one way to test the OVM.=C2- Most people would prefer
a simple push button test.
A perfectionist might want to go to the trouble of testing the complete cir
cuit with actual voltage that is too high.
Some people want an indicator light to tell if the OVM tripped the alternat
or field breaker, thus saving troubleshooting time.
Maybe there is way to accomplish that using solid state components instead
of a latching relay.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511490#511490
-
S -
WIKI -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
Message 9
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| Subject: | Re: OVM14 MkIII, rev P1 |
At 02:29 PM 9/25/2023, you wrote:
>
>There is more than one way to test the OVM. Most people would
>prefer a simple push button test.
The current configuration COULD be
implemented with a panel push button.
However, without specific instructions
on usage, what's likelihood of it being
'over used'? I am aware of no ov management
system on TC or EX aircraft with any
sort of a in-situ test feature.
So installing a button labeled press-to-test
will be deduced by 99.9% of pilots as
something you can punch any time as
often as you like. That's what the avionics
and instrumentation tests do.
>A perfectionist might want to go to the trouble of testing the complete
>circuit with actual voltage that is too high.
Perhaps an individual who doesn't know
how the thing works in the first place?
>Some people want an indicator light to tell if the OVM tripped the
>alternator field breaker, thus saving troubleshooting time.
Really? What's the hurry? If the breaker
is out, something is broke. A simple
process of manipulation + observation
will deduce root cause. If the breaker is
out and the device checked good in
recent weeks, you're 90+ percent sure
it's an ov event.
Like any in-flight breaker operation,
you can generally reset one time. Watch
bus voltage. If it's an ov condition,
there will be a slight delay in the breaker
re-opening and a corresponding bump in
bus voltage exceeding 15v. If it's a dead
short, the breaker trips immediately with
no 'bump'. If it's an intermittent or
soft overload, the breaker may stay in
and bus voltage comes rises from battery to
normal alternator voltage and no 'bump'.
In the later case, you've got a bigger
can of worms. In the first two cases,
choice of root causes is pretty limited
but the process takes the same amount
of time irrespective of which gremlin
is being outted.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 10
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>Symptoms:
>1. A loud short-duration "crackle" occurs randomly every 3 to 10
>seconds accompanied by a RECEIVE indication on the face of the radio.
This suggests that the noise is coming in thru
the antenna. Try disconnecting the antenna to
see if noise goes away. Also, noises coming in
thru this pathway are affected by the radio's
volume control.
>2. Only happens when engine is running
Does turning alternator on/off make and difference?
Does running one mag at a time make a difference?
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 11
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| Subject: | Re: OVM14 MkIII, rev P1 |
nuckolls.bob(at)aeroelect wrote:
> The current configuration COULD be implemented with a panel push button.
I imagined the PTT mounted on short wires, tied into the wiring harness for the
OVM and inaccessible to the pilot in flight. During oil changes or condition
inspections -- when the cowling is already off -- close the PTT, conduct the
test, then open the PTT. No risk of over-use and if properly documented in the
Operating Handbook, future owners will know what to do with it too.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511500#511500
Message 12
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| Subject: | Re: OVM14 MkIII, rev P1 |
Joe Gores wrote:
> There is more than one way to test the OVM. Most people would prefer a simple
push button test.
> A perfectionist might want to go to the trouble of testing the complete circuit
with actual voltage that is too high.
That's what's so clever about Bob's PTT: it relies on the complete circuit to accomplish
the test by changing the sensed voltage slightly when the button is
pushed. It tests everything, but there's no need to disconnect the module or
apply an actual overvoltage to the bus. As he mentioned elsewhere, it targets
a point just below normal bus voltage and trips when the charging system is turned
on, which roughly verifies calibration as well as operation.
> Some people want an indicator light to tell if the OVM tripped the alternator
field breaker, thus saving troubleshooting time.
> Maybe there is way to accomplish that using solid state components instead of
a latching relay.
Just for the sake of conversation, and leaving aside the argument about whether
or not it's a good idea, yes, there is: in addition to triggering the SCR, the
delay timing comparator could also activate other output circuitry. No additional
logic or relays required.
-----
Regarding the last couple of sentences in my comments on Bob's schematic...
Eric Page wrote:
> Could you describe how to calculate the effect of closing the PTT switch (connecting
5.9k from 8V to the junction of R8 and R7)? I'm at a loss as to how that
works; it might as well be witchcraft!
...I found a nice set of tutorials...
https://www.allaboutcircuits.com/textbook/direct-current/chpt-10/what-is-network-analysis/
...that explain several ways to calculate the values in his PTT circuit. It turns
out not to be witchcraft after all!
-Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511502#511502
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