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1. 04:13 AM - Re: Re: Intercom question (Dan Brown)
2. 06:41 AM - Re: Re: Intercom question (Robert L. Nuckolls, III)
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| Subject: | Re: Intercom question |
Just read the article ...very cool!
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of jrevens
Sent: Saturday, February 07, 2015 12:15 AM
Subject: AeroElectric-List: Re: Intercom question
Thanks, Bob. It looks like they are going to use aviation headsets...
probably donated units of various brands. Not everyone has to necessarily be
able to "transmit" (push-to-talk) to the other headsets - perhaps only 1 or
2 ("pilot" & "co-pilot"), & everyone else able to hear at least. The mock-up
is basically of the nose section, so maximum distances of wire runs would be
approximately 10 or 15 feet. The leaders of this project feel that it will
add to the experience if the kids can connect in this way. BTW, this project
is written about in the latest "Sport Aviation" magazine on p.110.
--------
John Evens
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=438150#438150
Message 2
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| Subject: | Re: Intercom question |
At 23:14 2015-02-06, you wrote:
>
>Thanks, Bob. It looks like they are going to use aviation
>headsets... probably donated units of various brands. Not everyone
>has to necessarily be able to "transmit" (push-to-talk) to the other
>headsets - perhaps only 1 or 2 ("pilot" & "co-pilot"), & everyone
>else able to hear at least. The mock-up is basically of the nose
>section, so maximum distances of wire runs would be approximately 10
>or 15 feet. The leaders of this project feel that it will add to the
>experience if the kids can connect in this way. BTW, this project is
>written about in the latest "Sport Aviation" magazine on p.110.
>
>--------
>John Evens
Understand. My recommendation is to start with
any sort of pre-packaged audio amplifier. One
like this would work nicely.
Emacs!
There are dozens of similar devices on eBay. I've
used a bunch in various applications with good
results and value. You can power them up with a
12v 'wall wart'. In fact, if you'll shoot me an
address, I donate an amplifier and power supply
to the project.
The next thing you need to do is cobble up the
interface that makes an aircraft microphone 'look'
like something found in the rest of the world . . .
Emacs!
A circuit like that shown above will allow
you to bias-up and mix as many microphones
together as needed. PTT for any particular
mic can be a simple n.c. push button in parallel
with the microphone. The button shorts out the
mic unless being used. This is preferable to
putting a n.o. button in series . . . the
parallel configuration reduces the DC level
shift and resulting 'pop' you hear in the system
as any one microphone is keyed.
Headphones can simply be paralleled assuming
they're all about the same efficiency where volume
can be managed by the single control on the amplifier.
Recommended circuitry not shown is a 220 ohm, 1/2
watt resistor in series with each line out to
a headset. At worst, you may have to balance
relative audio levels in the headsets which
can be accomplished by adjusting the value of that
220 ohm resistor.
Got somebody in your group that's handy
slinging solder?
Bob . . .
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