automatic switch
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Posts: 46,084
Hello everyone,
Using the basic stamp, I would like to build a device for my brother
who's a pilot. It would allow him to listen to music (probably by
connecting his headphones to a discman or walkman) but still able him
to receive the control tower transmissions, both using the same
headphones. So it would be a matter of making an "automatic switch".
So what I'm trying to do is program the stamp so that the tower
frequency input would be given more importance, thus transferring its
messages instead of music.
I have no clear idea of what to do yet, all I know is I'd like this
thing to be a little box with three audio jacks, two for input (music
+ control tower), and one for output (headphones). Have the stamp do
the work and switch between both when required.
I was told that I would probably need analog to digital components...
Do you have any suggestion ? I have searched the web, and this
message group, but haven't really found anything similar. Anything
would help. Thanks for reading. [noparse]:)[/noparse]
Using the basic stamp, I would like to build a device for my brother
who's a pilot. It would allow him to listen to music (probably by
connecting his headphones to a discman or walkman) but still able him
to receive the control tower transmissions, both using the same
headphones. So it would be a matter of making an "automatic switch".
So what I'm trying to do is program the stamp so that the tower
frequency input would be given more importance, thus transferring its
messages instead of music.
I have no clear idea of what to do yet, all I know is I'd like this
thing to be a little box with three audio jacks, two for input (music
+ control tower), and one for output (headphones). Have the stamp do
the work and switch between both when required.
I was told that I would probably need analog to digital components...
Do you have any suggestion ? I have searched the web, and this
message group, but haven't really found anything similar. Anything
would help. Thanks for reading. [noparse]:)[/noparse]
Comments
u could probley get away with simple eletronics useing transistors
and what not to some how "switch " the two different inputs or even
use some sort of amplifer so it will decrease the volume while the
tower is talking then once it fades away raise volume back up from
the music.... but useing a stamp u would probley need some form of
analog digital converter's or a transistor switch , so when one of
the analog lines have a volume grater then 0' or just the back ground
noise, it will tell stamp to say switch a reley that will change the
music into the tower trasnmiting, and once the tower's volume droped
back to 0' it auto switch back and keep looping the program over and
over....
just a thought...
Sean
--- In basicstamps@yahoogroups.com, "JBK" <samyuvel@h...> wrote:
> Hello everyone,
>
> Using the basic stamp, I would like to build a device for my
brother
> who's a pilot. It would allow him to listen to music (probably by
> connecting his headphones to a discman or walkman) but still able
him
> to receive the control tower transmissions, both using the same
> headphones. So it would be a matter of making an "automatic switch".
> So what I'm trying to do is program the stamp so that the tower
> frequency input would be given more importance, thus transferring
its
> messages instead of music.
>
> I have no clear idea of what to do yet, all I know is I'd like this
> thing to be a little box with three audio jacks, two for input
(music
> + control tower), and one for output (headphones). Have the stamp
do
> the work and switch between both when required.
> I was told that I would probably need analog to digital
components...
>
> Do you have any suggestion ? I have searched the web, and this
> message group, but haven't really found anything similar. Anything
> would help. Thanks for reading. [noparse]:)[/noparse]
> Hello everyone,
> I have no clear idea of what to do yet, all I know is I'd like this
> thing to be a little box with three audio jacks, two for input (music
> + control tower), and one for output (headphones). Have the stamp do
> the work and switch between both when required.
> I was told that I would probably need analog to digital components...
Yowie!! This kind of casual tinkering with critical saftey
issues never ceases to amaze me! My first suggestion would be
to check with the FAA... I am almost positive that your idea is
highly illegal. If your device were to fail your brother could
miss an instruction from the FAA or tower control and cruise
into a 747 (but he won't miss a note from his favorite group...)
have you (or your brother) really thought this through?
Transmitter/Reciever designs for aircraft must be certified - I
hardly doubt that one can interface an uncertified device into
the reception stream (god, as an airline passenger I hope not).
My concience alone wouldn't let me assist in such a scheme - let
alone the potiental liability...
Please think about this some more...
Michael
> issues never ceases to amaze me! My first suggestion would be
> to check with the FAA... I am almost positive that your idea is
> highly illegal. If your device were to fail your brother could
> miss an instruction from the FAA or tower control and cruise
> into a 747 (but he won't miss a note from his favorite group...)
> have you (or your brother) really thought this through?
>
> Transmitter/Reciever designs for aircraft must be certified - I
> hardly doubt that one can interface an uncertified device into
> the reception stream (god, as an airline passenger I hope not).
>
> My concience alone wouldn't let me assist in such a scheme - let
> alone the potiental liability...
>
> Please think about this some more...
>
> Michael
Yes, I did think about such issues, don't worry. [noparse]:)[/noparse]
To be frank, this idea sparked from a conversation between him and
me, but now has been reduced to something a lot less "ambitious" in
what the use could be. Meaning = it will most likely never be used by
pilots (the "most likely" part means I'd have it officially tested).
So the whole "for my brother" part was nothing more than an
introductory text. :-x
Right now this project is down to only trying to make something that
would automatically switch between two audio sources, not applicable
to flying planes. Plus, the headphones pilots use are both input and
output (they have a mic), and this is something I'm not ready to go
into. So the project I have actually WOULD NOT be applicable to
planes AT ALL. It is perfectly clear to me, and I'm not trying to
find ways around it. Ultimately, this thing will never be on a plane.
Now, since we're on the subject, while thinking about it, I did see
some similarities with actual devices. When you're on a plane, the
music / soundtrack of a movie always turns off when the pilot has
something to say. That would be the same principle, wouldn't it ? I
wouldn't be extremely surprised if the pilots already had something
to listen to music with... Not saying my project would be used for
that, just thinking aloud.
Sorry if I wasn't clear the first time. I should have taken some more
time to describe what is on my mind. [noparse]:)[/noparse]
There is a reason there is not much amateur stuff for airplanes on this site.
The issue's of safety and legality.
If the circuit fails and does not switch back to the radio in a critical
phase of flight, bye bye brother. The circuit could damage the radio to the same
end.
The FAA also very closely regulates what goes into an airplane, and who works
on it. You can change your own spark plugs, but you cannot set the gap. You
have to be a licensed mechanic for that.
Save your time and buy an aircraft approved intercom. Sigtronics is one of
the big names. Check Sportys Pilot Shop (www.sportys.com).
Any pilots magazine has ads for all the big players in the intercom market,
and they have models with inputs for music. Yes, they cost more, but they
already went through the approval process.
Hope this helps.
Alan Bradford
Plasma Technologies
In a message dated 11/21/2003 8:42:36 PM Eastern Standard Time,
samyuvel@h... writes:
Hello everyone,
Using the basic stamp, I would like to build a device for my brother
who's a pilot. It would allow him to listen to music (probably by
connecting his headphones to a discman or walkman) but still able him
to receive the control tower transmissions, both using the same
headphones. So it would be a matter of making an "automatic switch".
So what I'm trying to do is program the stamp so that the tower
frequency input would be given more importance, thus transferring its
messages instead of music.
I have no clear idea of what to do yet, all I know is I'd like this
thing to be a little box with three audio jacks, two for input (music
+ control tower), and one for output (headphones). Have the stamp do
the work and switch between both when required.
I was told that I would probably need analog to digital components...
Do you have any suggestion ? I have searched the web, and this
message group, but haven't really found anything similar. Anything
would help. Thanks for reading. [noparse]:)[/noparse]
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
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[noparse][[/noparse]Non-text portions of this message have been removed]
> planes AT ALL. It is perfectly clear to me, and I'm not trying to
> find ways around it. Ultimately, this thing will never be on a plane.
Yeah right... something's not adding up because your exact words
were pretty clear... and I quote;
"It would allow him to listen to music (probably by connecting
his headphones to a discman or walkman) but still able him to
receive the control tower transmissions,"
AND
"So what I'm trying to do is program the stamp so that the tower
frequency input would be given more importance, thus
transferring its messages instead of music."
Think I'll pass.... makes me real nervous when the story changes
this radically - both can't be true and I'm inclined to put more
weight on your first version which is courting disaster.
Michael
> this radically - both can't be true and I'm inclined to put more
> weight on your first version which is courting disaster.
Your choice, thanks for reading anyway.
The truth is, this is a student project. I wrote the original message
last Monday, sent it, but it didn't get through and I got the message
back. Next, I went to class, talked about the project, and there it
changed. Then, still needing a bit of help from this group here, I
just copied and pasted the original message and sent it, succesfuly
this time.
Now you know exactly what happened. If you still have a problem with
this project, I guess I can't do much about it.
I repeat : I'm just trying to make this automatic switch thing, with
no intent at all of getting it on planes. I'm sorry I didn't take the
time to edit the obsolete original message before posting.
Conversation so far has raised a few interesting problems, so I thank
you for that. [noparse]:)[/noparse]
Can anybody provide a bit of technical help though ? Right now the
most realistic use for this project would be to fade the music down
on walkmans/discmans when an outside source (person, car honk... or
for testing purposes, another walkman) acts as input.
starters I suggest that you need to address the following areas in your
design planning
1) Lay out a block diagram for each function. Show how they are related to
each other by lines between the blocks. Define functions, signal levels,
data control lines etc.
2) decide what boxes are active that need power and those that are passive
that do not need power.
3) From the Radio and the CDplyr what are the average signal levels and what
is their dynamic range?
4) What impedance are they now? What impedance will you make the
transmission paths?
5) At what signal level from the Radio do I want to switch off the Audio
from the CD and leave the radio as the only active source. What if the
signal level is just above the noise. How much gain must my signal presence
detector require?
6) Draw a flow chart or a sequence document of what you want to happen, when
it happens. What are the pre requisites for an event to occur, What are the
results of an event happening?
7) What do you want to happen under a fault condition. eg: Who gets
connected to what when their is no power?
How are you going to alert someone when the transmission path between the
Radio and the headphones has failed?
Plan Plan Plan Plan. This is an iterative process.
Do not select a solution before you have planned your design.
Regards, Steve Chapman
Original Message
From: "JBK" <samyuvel@h...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, November 22, 2003 3:37 PM
Subject: [noparse][[/noparse]basicstamps] Re: automatic switch
> > Think I'll pass.... makes me real nervous when the story changes
> > this radically - both can't be true and I'm inclined to put more
> > weight on your first version which is courting disaster.
>
>
> Your choice, thanks for reading anyway.
>
> The truth is, this is a student project. I wrote the original message
> last Monday, sent it, but it didn't get through and I got the message
> back. Next, I went to class, talked about the project, and there it
> changed. Then, still needing a bit of help from this group here, I
> just copied and pasted the original message and sent it, succesfuly
> this time.
>
> Now you know exactly what happened. If you still have a problem with
> this project, I guess I can't do much about it.
>
> I repeat : I'm just trying to make this automatic switch thing, with
> no intent at all of getting it on planes. I'm sorry I didn't take the
> time to edit the obsolete original message before posting.
>
> Conversation so far has raised a few interesting problems, so I thank
> you for that. [noparse]:)[/noparse]
>
> Can anybody provide a bit of technical help though ? Right now the
> most realistic use for this project would be to fade the music down
> on walkmans/discmans when an outside source (person, car honk... or
> for testing purposes, another walkman) acts as input.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>
no rule that the pilot can't be listening to music during flight. So you
saying its not safe? Well apparently he's doing it now. But is he listening
to the tower at the same time? Ummm ...
This project is real simple to do. You don't need any A/D conversions at
all. In fact using a BS would be an overkill. It can be easily done using a
couple of low noise op-amps, PNP transistor, and a few discrete components.
If the tower conversations take precedence over the walkman then the
tower input can be 'hot' or 'on' at all times. on when the tower is
transmitting it would 'kill' the walkman threw the PNP switch. Can you see
where I'm going with this?
as someone pointed out, pay attention to impedance matching of the tower
output and walkman output. add the necessary components to the
non-inverting input side of the op-amps.
I'm just brainstorming here but I have done several op-amp projects over
the years.
first take OPAMP1 with Z in = tower, gain=1 going to mixer to output OPAMP2
second take OPAMP2 with Z in = walkman, gain=1 going threw PNP switch to
mixer to output
The PNP would be bias just below the DC offset from the tower. so when
tower is off PNP is on. Tower is on PNP is off. remember it takes positive
bias to turn it off.
Z out or output impedance is set to match the users headphones. the mixer
is simply a couple of resistors tied to the same input pin of the output
op-amp.
as some add-on options:
* could add a LM386 1 watt amp to be used as a headphone amplifier
* add a bass and treble pots or maybe 5-band digital EQ
* add a integrator with a slow RC time constant to the PNP switch
this would cause the volume of walkman to slowly increase after
tower turns off.
The same principle applies to wal-mart or grocery stores intercom system.
where they interrupt your favorite song to announce "clean-up in aisle
7" this may get you going in the right direction. I guess if you need
them I could whip up some schematics in my spare time.
more ramblings later
Daryl Berryhill
djberry@h...
At 07:37 PM 11/21/2003, you wrote:
>Hello everyone,
>
>Using the basic stamp, I would like to build a device for my brother
>who's a pilot. It would allow him to listen to music (probably by
>connecting his headphones to a discman or walkman) but still able him
>to receive the control tower transmissions, both using the same
>headphones. So it would be a matter of making an "automatic switch".
>So what I'm trying to do is program the stamp so that the tower
>frequency input would be given more importance, thus transferring its
>messages instead of music.
>
>I have no clear idea of what to do yet, all I know is I'd like this
>thing to be a little box with three audio jacks, two for input (music
>+ control tower), and one for output (headphones). Have the stamp do
>the work and switch between both when required.
>I was told that I would probably need analog to digital components...
>
>Do you have any suggestion ? I have searched the web, and this
>message group, but haven't really found anything similar. Anything
>would help. Thanks for reading. [noparse]:)[/noparse]
>
>
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
the problem, but it seems to me that a pure analog circuit is a better
choice than anything involving a microprocessor.
Add a simple mixer, and clamp channel A (your walkman) if there's a decent
signal level on any other channel. If you want to pick up ambient sounds,
you'll need a microphone as well.
http://www.discovercircuits.com/A/au-mixer.htm has a bunch of examples, but
you'll need to designate a priority channel by clamping the other channels
when the priority channel is active.
If you would like to explore the amazing magic that starts happening when
you mix Audio with Digital Controls,
http://www.biamp.com specializes in adaptive systems for Courtrooms and
Auditoriums
http://www.iedaudio.com specializes in Digitized store and forward systems
for Aviations Voice Paging Systems.
Original Message
From: "JBK" <samyuvel@h...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, November 22, 2003 3:37 PM
Subject: [noparse][[/noparse]basicstamps] Re: automatic switch
> > Think I'll pass.... makes me real nervous when the story changes
> > this radically - both can't be true and I'm inclined to put more
> > weight on your first version which is courting disaster.
>
>
> Your choice, thanks for reading anyway.
>
> The truth is, this is a student project. I wrote the original message
> last Monday, sent it, but it didn't get through and I got the message
> back. Next, I went to class, talked about the project, and there it
> changed. Then, still needing a bit of help from this group here, I
> just copied and pasted the original message and sent it, succesfuly
> this time.
>
> Now you know exactly what happened. If you still have a problem with
> this project, I guess I can't do much about it.
>
> I repeat : I'm just trying to make this automatic switch thing, with
> no intent at all of getting it on planes. I'm sorry I didn't take the
> time to edit the obsolete original message before posting.
>
> Conversation so far has raised a few interesting problems, so I thank
> you for that. [noparse]:)[/noparse]
>
> Can anybody provide a bit of technical help though ? Right now the
> most realistic use for this project would be to fade the music down
> on walkmans/discmans when an outside source (person, car honk... or
> for testing purposes, another walkman) acts as input.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
components and circuit suggestions.
Daryl -
"I guess if you need them I could whip up some schematics in my spare
time."
Sure, if that's not too much trouble for you. Thanks a lot. [noparse]:D[/noparse]
--- In basicstamps@yahoogroups.com, "MarvL" <MarvL@m...> wrote:
> Your comment "or another Walkman, for testing purposes" really
simplifies
> the problem, but it seems to me that a pure analog circuit is a
better
> choice than anything involving a microprocessor.
>
> Add a simple mixer, and clamp channel A (your walkman) if there's a
decent
> signal level on any other channel. If you want to pick up ambient
sounds,
> you'll need a microphone as well.
> http://www.discovercircuits.com/A/au-mixer.htm has a bunch of
examples, but
> you'll need to designate a priority channel by clamping the other
channels
> when the priority channel is active.
this) is that airplanes are FAA certified and you are required to get
approval to modify anything on them.
To be on the safe side, this would mean any circuit would need to be
exteranl and not a hard wired installation.
Simple enough to do that in any event.
the sense circut would just monitor the output of the radio and as
soon as there was any noise, it would switch to the radio.
I would offer that you should also include a time delay so that it
switches to the radio, and stays on that for some 20 seconds, before
switching back to the CD.
Ask your friend, longer may be better as if one gets instructions
from the tower or another aircraft, you don't wanna hear Pink Floyd
while jotting down notes.
Possibly a manual reset is in order. that way, the radio takes
precidence and the pilot makes the choices on what to do next.
And, that switch could easily fit on the mic plug/adapter. it would
need to be EASY to reach.
Dave
in a P28.
We connect a CD player in the jack and thats it.
Both (CD and COM) have a different volume knob, so.. you never miss anything
from what they saying.
You never have to listen constant to the control tower.
And mostly, you can predict where and when you can expect Control will
contact you.
Tehre is no law that forbids you to listen to the music.
Airline pilots, flying long distances even read there newspapers with there
legs on the dasboard.
Oorspronkelijk bericht
Van: JBK [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=skCcZawgFfz-2bo71cH3HuhGJiHZmAcTd7FLw0fMKVMvfOyJDH53vOcU1mUL0P1l7JWdNsMyDemGNMkC0w]samyuvel@h...[/url
Verzonden: zaterdag 22 november 2003 8:38
Aan: basicstamps@yahoogroups.com
Onderwerp: [noparse][[/noparse]basicstamps] Re: automatic switch
> Yowie!! This kind of casual tinkering with critical saftey
> issues never ceases to amaze me! My first suggestion would be
> to check with the FAA... I am almost positive that your idea is
> highly illegal. If your device were to fail your brother could
> miss an instruction from the FAA or tower control and cruise
> into a 747 (but he won't miss a note from his favorite group...)
> have you (or your brother) really thought this through?
>
> Transmitter/Reciever designs for aircraft must be certified - I
> hardly doubt that one can interface an uncertified device into
> the reception stream (god, as an airline passenger I hope not).
>
> My concience alone wouldn't let me assist in such a scheme - let
> alone the potiental liability...
>
> Please think about this some more...
>
> Michael
Yes, I did think about such issues, don't worry. [noparse]:)[/noparse]
To be frank, this idea sparked from a conversation between him and
me, but now has been reduced to something a lot less "ambitious" in
what the use could be. Meaning = it will most likely never be used by
pilots (the "most likely" part means I'd have it officially tested).
So the whole "for my brother" part was nothing more than an
introductory text. :-x
Right now this project is down to only trying to make something that
would automatically switch between two audio sources, not applicable
to flying planes. Plus, the headphones pilots use are both input and
output (they have a mic), and this is something I'm not ready to go
into. So the project I have actually WOULD NOT be applicable to
planes AT ALL. It is perfectly clear to me, and I'm not trying to
find ways around it. Ultimately, this thing will never be on a plane.
Now, since we're on the subject, while thinking about it, I did see
some similarities with actual devices. When you're on a plane, the
music / soundtrack of a movie always turns off when the pilot has
something to say. That would be the same principle, wouldn't it ? I
wouldn't be extremely surprised if the pilots already had something
to listen to music with... Not saying my project would be used for
that, just thinking aloud.
Sorry if I wasn't clear the first time. I should have taken some more
time to describe what is on my mind. [noparse]:)[/noparse]
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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wrote:
> The device you wonna build is a STANDARD feature of the comradio
i'm using
> in a P28.
> We connect a CD player in the jack and thats it.
> Both (CD and COM) have a different volume knob, so.. you never miss
anything
> from what they saying.
> You never have to listen constant to the control tower.
> And mostly, you can predict where and when you can expect Control
will
> contact you.
> Tehre is no law that forbids you to listen to the music.
> Airline pilots, flying long distances even read there newspapers
with there
> legs on the dasboard.
Listening and relaxing are wholly different than modifying installed
equipment.
if the new item plugs into the headset jack and in entirely exteranl
to fixed equipement, there MAY not be a problem, although you should
seek advise from the local FAA rep.
Airplanes are highly regulated, If I'm not mistaken you are not
allowed to change the oil unless you are liscensed.
Dave
This guy is obviously NOT an FAA certified electronics tech.
Therefore....any pilot that lets someone in to their plane to "MOD/INSTALL"
anything, without said certification, would obviously lose his license as
well as be fined along with this guy.
Those airplane gambling machines had to be certified as well, and they had
NOTHING to do with navigation systems...sure the wiring caused fires....but
isn't the FAA a gov't machine (not efficient!)
So....don't crucify this guy too much.
Original Message
From: Dave Mucha [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=nIAg3FLniC2Voa_gMTrPaRu6-gvN-OzCuJ1edO-XMeVGrT2zsJjqvo1McqaiSwRiep29UqRlRyjh]davemucha@j...[/url
Sent: November 23, 2003 18:09
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: automatic switch
One thing I didn't see mentioned (but I haven't read every post on
this) is that airplanes are FAA certified and you are required to get
approval to modify anything on them.
To be on the safe side, this would mean any circuit would need to be
exteranl and not a hard wired installation.
Simple enough to do that in any event.
the sense circut would just monitor the output of the radio and as
soon as there was any noise, it would switch to the radio.
I would offer that you should also include a time delay so that it
switches to the radio, and stays on that for some 20 seconds, before
switching back to the CD.
Ask your friend, longer may be better as if one gets instructions
from the tower or another aircraft, you don't wanna hear Pink Floyd
while jotting down notes.
Possibly a manual reset is in order. that way, the radio takes
precidence and the pilot makes the choices on what to do next.
And, that switch could easily fit on the mic plug/adapter. it would
need to be EASY to reach.
Dave
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is a radio communication on their channel??
Or at least an audible beep. They must have redundancy of their own (not
just the co-pilot!)
Original Message
From: TLD-NV [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=bfg_s_Je5r504ikCjW55y41jf0BvvrZiXyzU_rsPykkF3ZuUhdCKw71SYCxdyPxEUrKxiefTumi63m8i-Mrzzfm4SEHQ]peter.christiaen@s...[/url
Sent: November 24, 2003 04:30
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Re: automatic switch
The device you wonna build is a STANDARD feature of the comradio i'm using
in a P28. We connect a CD player in the jack and thats it. Both (CD and COM)
have a different volume knob, so.. you never miss anything from what they
saying. You never have to listen constant to the control tower. And mostly,
you can predict where and when you can expect Control will contact you.
Tehre is no law that forbids you to listen to the music. Airline pilots,
flying long distances even read there newspapers with there legs on the
dasboard.
Oorspronkelijk bericht
Van: JBK [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tpwdFc7OafYr95XFGGn-VztZpN5NJordqOePQ4MO-0fF1prqTapz7LVwl2TH_lr0lyfQLVvNfRRyXIwqzStS]samyuvel@h...[/url
Verzonden: zaterdag 22 november 2003 8:38
Aan: basicstamps@yahoogroups.com
Onderwerp: [noparse][[/noparse]basicstamps] Re: automatic switch
> Yowie!! This kind of casual tinkering with critical saftey issues
> never ceases to amaze me! My first suggestion would be to check with
> the FAA... I am almost positive that your idea is highly illegal. If
> your device were to fail your brother could miss an instruction from
> the FAA or tower control and cruise into a 747 (but he won't miss a
> note from his favorite group...) have you (or your brother) really
> thought this through?
>
> Transmitter/Reciever designs for aircraft must be certified - I hardly
> doubt that one can interface an uncertified device into the reception
> stream (god, as an airline passenger I hope not).
>
> My concience alone wouldn't let me assist in such a scheme - let alone
> the potiental liability...
>
> Please think about this some more...
>
> Michael
Yes, I did think about such issues, don't worry. [noparse]:)[/noparse]
To be frank, this idea sparked from a conversation between him and me, but
now has been reduced to something a lot less "ambitious" in what the use
could be. Meaning = it will most likely never be used by pilots (the "most
likely" part means I'd have it officially tested). So the whole "for my
brother" part was nothing more than an introductory text. :-x
Right now this project is down to only trying to make something that would
automatically switch between two audio sources, not applicable to flying
planes. Plus, the headphones pilots use are both input and output (they have
a mic), and this is something I'm not ready to go into. So the project I
have actually WOULD NOT be applicable to planes AT ALL. It is perfectly
clear to me, and I'm not trying to find ways around it. Ultimately, this
thing will never be on a plane.
Now, since we're on the subject, while thinking about it, I did see some
similarities with actual devices. When you're on a plane, the music /
soundtrack of a movie always turns off when the pilot has something to say.
That would be the same principle, wouldn't it ? I wouldn't be extremely
surprised if the pilots already had something to listen to music with... Not
saying my project would be used for that, just thinking aloud.
Sorry if I wasn't clear the first time. I should have taken some more time
to describe what is on my mind. [noparse]:)[/noparse]
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> Tehre is no law that forbids you to listen to the music.
> Airline pilots, flying long distances even read there newspapers with there
> legs on the dasboard.
You're missing the point completely. The issue is not listening
to music... the issue is putting non-certified communications
hardware in the communications stream in such a way as to force
the FAA communications thru the non-certified hardware in able
to be heard by the pilot.
If such hardware were to malfunction *critical* FAA instructions
could be completely missed by the pilot.
Michael
> You're missing the point completely. The issue is not listening
> to music... the issue is putting non-certified communications
> hardware in the communications stream in such a way as to force
> the FAA communications thru the non-certified hardware in able
> to be heard by the pilot.
At the risk of bad form for following up on my own posting -
from the FAA Regulations:
43.3(a) Except as provided in this section and § 43.17, no
person may maintain, rebuild, *alter*, or perform preventive
maintenance on an aircraft, airframe, aircraft engine,
propeller, *appliance*, or component part to which this part
applies. Those items, the performance of which is a major
alteration, a major repair, or preventive maintenance, are
listed in appendix A.
Appendix A (4) *Appliance major alterations*.
Alterations of the basic design not made in accordance with
recommendations of the appliance manufacturer or in accordance
with an FAA Airworthiness Directive are appliance major
alterations. In addition, changes in the basic design of radio
communication and navigation equipment approved under type
certification or a Technical Standard Order that have an effect
on frequency stability, *noise level*, *sensitivity*,
*selectivity*, distortion, spurious radiation, AVC
characteristics, or ability to meet environmental test
conditions and other changes that have an effect on the
performance of the equipment are also major alterations.
Michael
> "TLD-NV" <peter.christiaen@s...> wrote:
>> The device you wonna build is a STANDARD feature of the
>> comradio I'm using in a P28.
>> We connect a CD player in the jack and thats it.
[noparse][[/noparse]...]
>> And mostly, you can predict where and when you can expect
>> Control will contact you.
>
> Listening and relaxing are wholly different than modifying installed
> equipment.
>
> if the new item plugs into the headset jack and in entirely exteranl
> to fixed equipement, there MAY not be a problem, although you should
> seek advise from the local FAA rep.
>
An FAA rep wouldn't have a lot to say I imagine, unless they are less busy
these days than they used to be. Anyone with a repair certificate at the
local FBO can describe the ground rules quickly. Unless they've changed
greatly it's pretty much what your intuition suggests:
If it's already installed, don't screw with it without someone with the
relevant certificate at least supervising -- and often they must do the work
personally.
If you plan to install something new, then you must obtain a sign-off from
that person that your installation does not affect the flight-critical
systems and to confirm that you have updated the weight and balance data
appropriately.
If it isn't something that is going to be installed, but instead is plugged
into existing equipment, then it's the pilot's judgment whether it will
affect safety of flight. The pilot can decide your Gameboy or Palm Pilot is
affecting safety of flight even though it's plugged into nothing at all, and
can require that it be turned off, or even that the batteries be removed --
and that judgment has the force of federal law. The pilot's own equipment is
similarly a matter of pilot discretion, both pro and con. So basically, it's
up to the pilot, whether it's a separate set of CD headsets or a portable
intercom with auto-switching between the radio stack and a CD. I imagine
modern stacks have an aux-input that can be used this way in any case, so
it's going to be the pilot's judgment what goes in that jack in any case.
I built my own intercom with that switching feature for use on long flights,
in the days when it was not a common option in the built-in equipment stack.
It isn't difficult because aviation radios all have a squelch feature. When
an incoming transmission has sufficient signal strength, it breaks
squelch -- otherwise the audio signal on the line is so many dB down, that
it's a piece of cake to put a detector on the line and disable the secondary
audio only when audio is detected on the primary. Personally, I found it a
pain in the neck anywhere near a large center, because Center is talking to
someone almost constantly so you never get more than a couple of bars of
music between their tranmissions. On the other hand, we flew up through the
Northwest Territories, and you might as well turn off the radios up there.
Basically, communications with air traffic control are almost never a matter
of safety at those times when the pilot would not be expecting them. In
fact, I can't think of a single example off hand, although there are some
I'm sure. Anything important comes at a time when the pilot expects to hear
a transmission. Since we know when ATC should be contacting us, we look for
a communication at that time, and if the controller screws up -- or a
hypothetical intercom flaw has blocked the communication -- then we call
them to wake them up. And for diplomacy's sake, we call that a "comm check."
"Denver Center, Piper 1234. Comm check. We did not receive your clearance to
begin descent at 1407. Please say again."
So if an intercom poses a problem, the safety issue lies with the pilot, not
the aircraft. As do most safety issues except the main spar breaking.
Sorry to get so far off topic. Just chatting.
Gary
wrote:
In fact using a BS would be an overkill. It can be easily done using
a
> couple of low noise op-amps, PNP transistor, and a few discrete
components.
After looking at all the options, I think this is the best one for
me. If it's going to be "simple" and if I can avoid programming,
that's really good. I'm still a beginner and don't have much time. [noparse]:)[/noparse]
Soooo... the only thing that wasn't clear is : what do you mean by "a
few discrete components" ? Sorry if it's something obvious, but I
have no idea what this is.
--- In basicstamps@yahoogroups.com, Daryl Berryhill <djberry@h...>
wrote:
> If the tower conversations take precedence over the walkman then
the
> tower input can be 'hot' or 'on' at all times. on when the tower
is
> transmitting it would 'kill' the walkman threw the PNP switch. Can
you see
> where I'm going with this?
> I'm just brainstorming here but I have done several op-amp
projects over
> the years.
> first take OPAMP1 with Z in = tower, gain=1 going to mixer to
output OPAMP2
> second take OPAMP2 with Z in = walkman, gain=1 going threw PNP
switch to
> mixer to output
> The PNP would be bias just below the DC offset from the tower. so
when
> tower is off PNP is on. Tower is on PNP is off. remember it takes
positive
> bias to turn it off.
> Z out or output impedance is set to match the users headphones.
the mixer
> is simply a couple of resistors tied to the same input pin of the
output
> op-amp.
Thanks for the suggestion, I'll see how I can do that...
0.01 microfarad capacitors for starters.
Soooo... the only thing that wasn't clear is : what do you mean by "a
few discrete components" ? Sorry if it's something obvious, but I
have no idea what this is.
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