Today's Message Index:
----------------------
1. 06:48 AM - (off topic) Aircraft Ground to the hangar floor when parked (toddheffley)
2. 07:27 AM - Re: (off topic) Aircraft Ground to the hangar floor when parked (Noel R.C. Loveys)
3. 08:40 AM - Re: (off topic) Aircraft Ground to the hangar floor when parked (Larry Mac Donald)
4. 12:12 PM - Re:LM3914 Bar Graph circuit question (MikeRV6-A)
5. 01:57 PM - Re: Re:LM3914 Bar Graph circuit question (Etienne Phillips)
6. 04:14 PM - Re: Battery Relay post too short (Robert L. Nuckolls, III)
7. 04:26 PM - Re: Re:LM3914 Bar Graph circuit question (Mike Welch)
8. 04:44 PM - Re: LM3914 Bar Graph circuit question (nuckollsr)
Message 1
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| Subject: | (off topic) Aircraft Ground to the hangar floor when |
parked
ALL
Sorry for the distractor... but I am on a quest for "Simple Science" FACTS to
rebuff some "Hanger Talk" about grounding aircraft when parked.
MOST military, some heavy maintenance bases , and a few General aviation facilities
provide and use ground wires to the hangar floor when aircraft are parked.
Why is that so???
The reasons I have gathered are:
1. "Grounds Out" static electricity when the aircraft is being polished (sounds
reasonable)
2. "Grounds Out" the airplane if the hangar is struck by lightening (sounds like
hanger talk)
3. Reduces Galvanic corrosion by dissimilar metals in the landing gear. ( sounds
like hanger talk)
4. Provides path to ground in the event of a 220VAC Ground Power Unit being wired
wrong and/or failure of the Green ground wire from the Mains supply (sounds
reasonable). This has been witnessed by one our staff.
5. Reduces chances of damage to ESD components, for example, when removing Printed
Circuit Cards from cages. (sounds reasonable)
6. Some Hanger Keepers insurance policies require it. (I have yet to see one...hanger
talk)
7. And finally, the most common answer.... Because the Army told me to ground the
airplane 30 years ago and I have been doing it ever since........(hanger talk
accepted blindly with no supporting rationale)
The accepted norms from several (Military) documents are:
--------
WWW.toddheffley.com
www.theinterconnectco.com for lighting products
AV-TS.com for Jet Aircraft Test Equipment
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323646#323646
Message 2
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| Subject: | (off topic) Aircraft Ground to the hangar floor |
when parked
If all aircraft in a hangar are bonded (grounded) to a common ground there
is no chance of a spark occurring between aircraft and all static is
immediately sent to ground.
The AMO (Authorized Maintenance Organization - Canada) I worked for did in
fact have a stipulation on the insurance requiring all aircraft on the
premises be bonded to ground, even the ones tied down outside. I never
actually saw the policy but I was told by the owner of the company such a
stipulation was in effect. On one occasion the insurance company did send
an inspector and he did check for grounds on all aircraft that may have fuel
in them.
Noel
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
toddheffley
Sent: December 17, 2010 11:14 AM
Subject: AeroElectric-List: (off topic) Aircraft Ground to the hangar floor
when parked
<public@toddheffley.com>
ALL
Sorry for the distractor... but I am on a quest for "Simple Science" FACTS
to rebuff some "Hanger Talk" about grounding aircraft when parked.
MOST military, some heavy maintenance bases , and a few General aviation
facilities provide and use ground wires to the hangar floor when aircraft
are parked.
Why is that so???
The reasons I have gathered are:
1. "Grounds Out" static electricity when the aircraft is being polished
(sounds reasonable)
2. "Grounds Out" the airplane if the hangar is struck by lightening (sounds
like hanger talk)
3. Reduces Galvanic corrosion by dissimilar metals in the landing gear. (
sounds like hanger talk)
4. Provides path to ground in the event of a 220VAC Ground Power Unit being
wired wrong and/or failure of the Green ground wire from the Mains supply
(sounds reasonable). This has been witnessed by one our staff.
5. Reduces chances of damage to ESD components, for example, when removing
Printed Circuit Cards from cages. (sounds reasonable)
6. Some Hanger Keepers insurance policies require it. (I have yet to see
one...hanger talk)
7. And finally, the most common answer.... Because the Army told me to
ground the airplane 30 years ago and I have been doing it ever
since........(hanger talk accepted blindly with no supporting rationale)
The accepted norms from several (Military) documents are:
--------
WWW.toddheffley.com
www.theinterconnectco.com for lighting products
AV-TS.com for Jet Aircraft Test Equipment
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323646#323646
Message 3
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| Subject: | Re: (off topic) Aircraft Ground to the hangar floor |
when parked
Tod,
I'll take a shot at this.
On hot,and particularly dry, days the fuel in the tanks will heat up and push the
fumes out of the vent. The fumes, being heavier than air, will sink to the
ground, asphalt, concrete or whatever. Should you rub against the plane or hit
something that will make a spark there is a fair chance the spark will detonate
the fume buildup on the ground. If the plane is grounded it will not contribute
to a spark. I hope.
Larry
On Dec 17, 2010, at 9:43 AM, toddheffley wrote:
>
> ALL
>
> Sorry for the distractor... but I am on a quest for "Simple Science" FACTS to
rebuff some "Hanger Talk" about grounding aircraft when parked.
>
> MOST military, some heavy maintenance bases , and a few General aviation facilities
provide and use ground wires to the hangar floor when aircraft are parked.
>
> Why is that so???
____________________________________________________________
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Message 4
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| Subject: | Re:LM3914 Bar Graph circuit question |
Hi Mike
If you would like to ensure that there is no cross-effect between
your bargraph measurement and the engine control circuit, you
can use a dual potentiometer. This is like the potentiometer
that you have, but it has two sections instead of one, and the
two sections are operated by the same shaft. This approach gives
you a signal for the bargraph that will track the mixture-control
signal without an electrical connection between the two.
To find a dual potentiometer at Digikey, enter "dual potentiometer"
in the search box. Also check the "in stock" box. In the next
screen you can find 5K linear potentiometers. The better-quality
potentiometers are not exactly cheap...
Mike Linse
>
> Hi guys,
>
> I have recently built the bar graph circuit suggested by Joe Gores.
> (This
> circuit incorporates the LM7805 5 volt regulator, and works off the Ray
> Allen
> servo potentiometer)
>
> Anyway, I got the circuit built and it works great!!! It lights the
> LEDs as I intended.
>
> In an unrelated circuit;
> I have a completely separate 5K ohm potentiometer that the engine uses
> for
> regulating fuel enrichment (via my manual adjustment). The 5K Pot is in
> place
> of the stock coolant thermister. By substituting my own 5K Pot in place
> of the
> non-adjustable thermister, I can regulate the 'cold engine' (high
> resistance) signal sent to the
> engine's ECU (computer), thereby making the engine think the engine is
> still cold,
> and subsequently enriching the fuel/air mixture.
> This is a VERY common modification on the GEO/Suzuki auto website, for
> guys that
> installed turbo chargers (like mine).
>
> My question is; does anyone have a suggestion how I can use that
> LM3914/LM7805
> circuit with my 5K potentiometer...and NOT affect the ohm reading it would
> have normally
> sent to the ECU if the circuit wasn't there.
>
> (For information purposes; The 5K Pot has 3 tabs. When turning the knob
> one
> direction, resistance between A & B goes from 0 to 5K, resistance from A
> to C
> goes from 5K to 0.)
>
> Mike Welch
Message 5
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| Subject: | Re:LM3914 Bar Graph circuit question |
Hi Mike(s)
Another point to ponder is that there are two types of potentiometers - linear
and logarithmic. The most common dual pots are logarithmic, as they're used as
volume controls in audio systems, where the logarithmic change in volume produces
a perceived linear fading.
The chances are good that for your fuel system, you will require a linear response.
To make sure, and to check what type the exiting pot is, with all power off
move the wiper to the middle of its range and check the resistance between
the middle and unconnected outer pin. If it's 2.5k, then it's a linear pot. If
it's 1k or 4k then it's logarithmic.
The bar-graph circuit will need a linear pot to be useful. If needed, you might
be able to find a log-lin dual pot if you scratch around enough.
Hope that helps!
Etienne
On 17 Dec 2010, at 9:30 PM, MikeRV6-A wrote:
>
> Hi Mike
>
> If you would like to ensure that there is no cross-effect between
> your bargraph measurement and the engine control circuit, you
> can use a dual potentiometer. This is like the potentiometer
> that you have, but it has two sections instead of one, and the
> two sections are operated by the same shaft. This approach gives
> you a signal for the bargraph that will track the mixture-control
> signal without an electrical connection between the two.
>
> To find a dual potentiometer at Digikey, enter "dual potentiometer"
> in the search box. Also check the "in stock" box. In the next
> screen you can find 5K linear potentiometers. The better-quality
> potentiometers are not exactly cheap...
>
> Mike Linse
>
Message 6
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| Subject: | Re: Battery Relay post too short |
At 02:15 PM 12/15/2010, you wrote:
>
>On the out going post of the master relay I feed the start relay and
>the main bus feed. In the attached photo you can see with just the
>fat wire going to the start relay it takes up most of the room on
>the post. I know most of the Z-diagrams show both connected to the
>master relay. How do you guys get another lug on there? I could
>leave off the lock washer but then how do you keep it from coming loose?
Lockwashers don't lock anything . . . especially when
you've got the overhang moments of the fat wires.
>One guy told me I could remove the nut that snugs up against the relay,
NO, NO, NO . . .
> but to make sure the post does not turn, one could replace this
> with a shorter nut and get more room that way. Not sure I want to
> risk moving the internal part, might work for a while but this
> could cause unknown issues.
Correct.
>More weight and parts but I guess I could connect the relay to a fat
>buss bar (maybe ANLs), then connect the start relay wire and the
>main bus feed wire to each.
Leave the lockwasher off. If you're confident of the
final positioning of wires, use a mild thread-locker
on the top nut. Otherwise wait until after your
fly-off. But risks for loosening are very low.
It would be really nice if they'd use a thin nut
against the case. It's not a big participant in
keeping things connected after all the nuts are on.
But taking that nut off event to replace it is to
risk mis-alignment of internal parts.
http://www.aeroelectric.com/Pictures/Contactors/S701-1a.jpg
In fact, it's REALLY a good idea to use a wrench
on the bottom nut to counter act torque for
final tightening of the top nut.
Bob . . .
Message 7
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| Subject: | Re:LM3914 Bar Graph circuit question |
> you can use a dual potentiometer.
> Mike Linse
Hi Mike=2C
Even though the dual potentiometer is fairly expensive=2C it sure does ac
complish
what I'm after in a simple=2C yet effective way.
I think I'll head in this direction=2C and while I'm getting stuff from D
igikey=2C I can
round up another LM3914 and LM7805.
Thanks for the suggestion=2C Mike. Also=2C Etienne=2C thanks for the poi
nters on the
differences between the two types of pots.
Mike Welch
Message 8
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| Subject: | Re: LM3914 Bar Graph circuit question |
I have a completely separate 5K ohm potentiometer that the engine uses for regulating
fuel enrichment (via my manual adjustment). The 5K Pot is in place of the
stock coolant thermister. By substituting my own 5K Pot in place of the non-adjustable
thermister, I can regulate the 'cold engine' (high resistance) signal
sent to the engine's ECU (computer), thereby making the engine think the engine
is still cold, and subsequently enriching the fuel/air mixture.
Mike, since the thermistor is a 2-wire device, your thermistor emulator potentiometer
is NOT being used as a potentiometer . . . but as a simple adjustable rheostat
(i.e. series resistor). From your post I presume you have an interest
in having a light-up bar graph that represents the potentiometer position over
full range of normal ops.
I think this can be done but it's a bit 'fussier' than the trim-indicator task
you've already mastered. How much of the pot's rotation is used for full range
of operations? Is this a vernier adjustment that is used to trim engine performance
during normal operations? Or is it a "set here for cold starting" and "set
there for operation?" Do you have some min-max markings on the pot's knob.
How many degrees of total potentiometer travel are represented by the min-max
pot settings?
The input impedance to the LM3914 is VERY high. The data sheet says bias current
into pin 5 is 100 NANO amps max, 25 nA typical. This kind of 'load' will have
no observable effect on the engine computer's perceptions of potentiometer position.
I would guess that one end of the "adjustable thermistor" is wired to ground. The
other goes to some current source within the ECU where voltage developed as
an effect of that current is translated to some temperature value. I would also
guess that the minimum voltage is not zero and the max voltage for normal operating
range does not require full rotation of the pot.
This means that your bar graph needs to be "differential". I.e. one led illuminated
at the operational low but not zero volts and all led's lit at max volts
(what ever that is). Can you get some measurements off an installed system for
min-max volts to be converted into a graphical display?
Bob . . .,
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323724#323724
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