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PTT Y adapter for RST intercom
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user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sat Nov 26, 2011 9:21 am Post subject: Re: PTT Y adapter for RST intercom

Different manufacturers could have various names for their products.  To me, a breadboard has spring loaded sockets to plug parts into.  A perforated board is what I had in mind, similar to the Radio Shack one that you referenced. Although soldered wires on the bottom of the perf board do not look good compared to a printed circuit board, it is a quick and easy way to make a circuit.  But nobody is going to see it anyway.  The important thing is that the project is mechanically and electrically sound.

  There are also ready-made generic printed circuit boards that may or may not have traces suitable for mounting relays. Digikey sells perforated board, i.e, 3396K-ND, and V2018-ND.  See http://media.digikey.com/pdf/Data%20Sheets/Vector%20PDFs/Vectorbord%20Circbord.pdf

It appears that V2018-ND has strips of copper on the back side for soldering parts and wires that are located on the top side.  Perhaps someone who has experience with these boards will comment.  If suitable, this type of board will make a nice looking project.

  The wiring diagram that you attached looks like one that might be printed on the side of a relay.  It is a schematic to show how to connect wires.  A schematic does not necessarily show the actual physical layout.  I would be very surprised if both sets of contacts did not operate simultaneously.

Joe

_________________
Joe Gores

messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Sat Nov 26, 2011 9:53 am Post subject: Re: PTT Y adapter for RST intercom

Yes, I just saw those boards at digikey. Of the two you mentioned, one is insulated, no plated holes. The other says 'continuous bus', which may not be what I need. At least I don't understand it. There's also another on the circbord.pdf link, #8029, which has plated holes. If I used the insulated non-plated one, soldering the terminals from the backside would hold the relay to the board in tension. With the plated one, I'd also have the terminals soldered directly to the plated board. Would the non-plated board connection be strong enough?

_________________
Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Nov 26, 2011 10:20 am Post subject: PTT Y adapter for RST intercom

At 11:21 AM 11/26/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com>



 Different manufacturers could have various names for their products.  To me, a breadboard has spring loaded sockets to plug parts into.  A perforated board is what I had in mind, similar to the Radio Shack one that you referenced. Although soldered wires on the bottom of the perf board do not look good compared to a printed circuit board, it is a quick and easy way to make a circuit.  But nobody is going to see it anyway.  The important thing is that the project is mechanically and electrically sound. 	


   I've dug out the internal schematics for the RST

   intercom and discovered that this is an INTERCOM

   with no integration-friendly features for tying

   it to one or more radios.



   As an intercom, I'm mystified as to the installation

   instructions that recommend opening the mic audio

   leads to each mic along with the PTT signal. I.e.

   a spring loaded, 2-pole, normally open push-button

   DPST OFF-(ON).



   If one adheres to this configuration, then it seems

   that the value of an adjustable silencing

   system (VOX, squelch, etc) is negated . . . the

   existence of these switches in the mic audio leads

   makes it a Push-to-Talk Intercom . . . not a VOX

   intercom.



   A study of the microphone input circuits to the

   intercom shows that power to run the microphone's

   electronics is provided internally to the intercom via

   the 2.2K resistors tied to the mic leads from the

   8v supply.



  http://www.aeroelectric.com/Installation_Data/RST/RST-442.pdf



 [img]cid:.0[/img]

   

   However, there are PILOT MIC OUT and COPILOT MIC OUT

   pins offered that "loop through" the intercom to

   service any other audio need . . . ostensibly a

   comm radio.



   This presents a bit of a quandry for the system

   integrator. To allow both mics of a two-pilot system

   to access the radio, one needs to tie the two signals

   together. Which puts 2 mic power sources in the

   intercom arm wrestling with each other and the

   third power source in the radio. Of course,

   breaking the mic audio lines with the PTT switch

   breaks one of those pathways while the system is

   in use via the other pathway.



   My suggestion:



   No relays, no DPST, OFF-(ON) buttons.



   Find connectors that mate with the pendant cables

   coming out of the intercom (Molex or Mate-m-Lock?)

   and set all that octopus of headset cables aside.



   Wire microphones as always-hot signal leads to

   their respective inputs on the intercom. Use the

   VOX system to control background noise when not

   speaking. Take the mic audio out leads from the

   intercom to a SPDT, ON-ON switch so that audio

   TO the DX-15 mic can be either pilot, co-pilot but

   not both.



   Wire as many single pole, SPST OFF-(ON) push

   buttons as desired to the DX-15 PTT line. I'll

   convert this description to a sketch as soon

   as I get some other chores taken care of.



   This is why the Dynon folks seemed to get stand-offish

   when asked for advice. Without having both access

   to internal working details of the intercom -AND-

   time to offer what amounts to gratis, customized

   system integration services, the guy didn't have

   a clue as to what MIGHT work. Even my suggestion

   has some risk that will have to shake out on the

   bench: While talking on the radio, the 2.2K mic-power

   bias resistors will be in parallel with what ever power

   comes from the DX-15. I'm surprised that those

   resistors are so large . . . their deleterious

   effects on the DX-15 audio may well be minimal.

   At the same time, it's possible that audio heard

   over the intercom will take a jump in perceived

   volume when transmitting. If that happens, we'll

   need to go to plan-B.



   In any case, I think a y-adapter only adds to

   the snarl of snakes generally associated with

   loose-in-the-cockpit intercom systems. It seems

   prudent to simplify this wiring to the greatest

   extent possible.



   It would be helpful to know the style of connector

   depicted in the RST drawing as "P101". A close-up photo

   would be useful. I think Jim was fond of the

   Molex mini nylon connectors back then but I

   need to confirm this.



 

 

   Bob . . .

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messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Sat Nov 26, 2011 11:41 am Post subject: Re: PTT Y adapter for RST intercom

 	  Quote: 	
		  As an intercom, I'm mystified as to the installation 

instructions that recommend opening the mic audio 

leads to each mic along with the PTT signal. I.e. 

a spring loaded, 2-pole, normally open push-button 

DPST OFF-(ON). 



If one adheres to this configuration, then it seems 

that the value of an adjustable silencing 

system (VOX, squelch, etc) is negated . . . the 

existence of these switches in the mic audio leads 

makes it a Push-to-Talk Intercom . . . not a VOX 

intercom. 	




I thought this and all intercoms could function independently from the radio. Thought it would work even if there wasn't a radio connected. The vox and/or squelch of the intercom would work in a closed system between the two headsets. 



I also thought placing these switches for the PTT's and mic's would not effect the intercom, since they are added between the intercom and the radio, not between the intercom and the headsets.

 	  Quote: 	
		  I'll 

convert this description to a sketch as soon 

as I get some other chores taken care of. 	




This would be very helpful. I tore apart the intercom box a few days ago and plan to mount just the squelch, volume and pilot/all controls permanently to the panel. I'll cut off all the wires to the Molex connections to be able to put everything behind the panel. The only cables coming out into view would be those connecting directly with the handheld radio mounted at the corner of the instrument panel and side panel. This would be the power, mic/ptt, and headphone, along with the antenna cable.

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Dan

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sat Nov 26, 2011 11:50 am Post subject: Re: PTT Y adapter for RST intercom

 	  Quote: 	
		  As an intercom, I'm mystified as to the installation instructions that recommend opening the mic audio leads to each mic along with the PTT signal. I.e. a spring loaded, 2-pole, normally open push-button DPST OFF-(ON).



If one adheres to this configuration, then it seems that the value of an adjustable silencing system (VOX, squelch, etc) is negated . . . the existence of these switches in the mic audio leads makes it a Push-to-Talk Intercom . . . not a VOX intercom. 	




Bob,

The RST documentation makes it hard to understand whether it is referring to MIC audio input to the intercom or the audio output from the intercom.  It took me awhile to realize that the questions that Dan was asking was about the output interface between the intercom and the hand-held radio.  The headsets and MICs are plugged directly into the intercom.  So as far as the intercom is concerned, the MICs are always connected.

  The relay circuit that I suggested is an interface between the intercom and the hand-held radio.  The relays do not open the headset MIC circuit to the intercom.  The MICs are always hot.  The relays choose which intercom audio output to connect to the hand-held radio.

  	  Quote: 	
		  . . .set all that octopus of headset cables aside . . . . It seems prudent to simplify this wiring to the greatest extent possible. 	


I agree with you.  It reminds me of the rat's nest of wires behind my computer.  

Perhaps Dan will figure out a way to install it so that all wires are behind the panel except for the cable that plugs into the radio.

Joe

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sat Nov 26, 2011 12:50 pm Post subject: Re: PTT Y adapter for RST intercom

Dan,

I just noticed that Digikey has a wiring diagram of the V2018-ND board.

http://www.vectorelect.com/Product/Circbord/Layout/8022%20Layout.pdf

The pins on a relay like Z768-ND will match the holes of the board.  Scratch a vertical line through the copper traces.  Mount the relay so that it straddles the scratched line.

Insert wires from the same side as the relay.

Solder the relays and wires to copper side of the board.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Nov 27, 2011 9:15 am Post subject: PTT Y adapter for RST intercom

At 11:28 PM 11/25/2011, you wrote:

 	  Quote: 	
		  



Nice 



Hadn't thought about this before, but I think the PTT relay grounds 

would go to a/c ground, and the other 4 would go to the radio jack 

sleeve, right?



I also looked around Digikey.com for the relays. It was hard to 

match the relays with sockets that are sold separately. I'm browsing 

through Ebay, which may have something.


	


  This relay . . .



http://search.digikey.com/us/en/products/G5V-2-DC12/Z768-ND/87821



  is suited to the task and fits in this socket



http://search.digikey.com/us/en/products/4-1571552-2/4-1571552-2-ND/2258924

   Bob . . .

messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Sun Nov 27, 2011 9:43 am Post subject: Re: PTT Y adapter for RST intercom

Thanks, Bob 



I understand these relays can be soldered to a perfboard. Joe had mentioned this, and I sorta forgot about the socket. Is there an advantage in using a socket, or could the relay be just as easily soldered directly onto a perfboard? I'd only be getting two of them and they're real cheap, so cost isn't an issue.

_________________
Dan

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Nov 27, 2011 9:48 am Post subject: Re: PTT Y adapter for RST intercom

Attached is a schematic that I drew of a single relay interface between RST-442 & Com radio. Only one MIC can be connected to the radio at a time.  I do not know if having the co-pilot MIC always connected to the radio hurts anything.  What do you think?

Joe

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Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Nov 27, 2011 10:19 am Post subject: Re: PTT Y adapter for RST intercom

 	  Quote: 	
		  Is there an advantage in using a socket, or could the relay be just as easily soldered directly onto a perfboard? 	


I think it is a matter of personal preference. A socket will make it easy to replace a defective relay.  The relay can not be damaged by heat from soldering if it is plugged into a socket.  Sometimes troubleshooting is made easier by unplugging a component from a socket.  But I prefer to solder parts directly to a PC board without using a socket, especially if subject to harsh environmental conditions.  Then I do not have to worry about a bad connection between the part and the socket.

Joe

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Nov 27, 2011 1:16 pm Post subject: Re: PTT Y adapter for RST intercom

See attached picture that shows how a perf board with copper strips can be used to make a project without having to acid etch a copper clad PC board.  While not suitable for complex circuits, simple circuits can be crafted by adding jumpers to the component side of the board.

Joe

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Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Nov 28, 2011 6:34 pm Post subject: PTT Y adapter for RST intercom

At 03:16 PM 11/27/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com>



 See attached picture that shows how a perf board with copper strips can be used to make a project without having to acid etch a copper clad PC board.  While not suitable for complex circuits, simple circuits can be crafted by adding jumpers to the component side of the board. 	


     Another options to consider . . .



 [img]cid:.0[/img]



   You could lay out a board like that shown above (actually, the

   layout is already done) and order them from Express PCB.

   Minimum order yields 18 boards in 3 days for about $69.



   This board would accept a solder-cup D-sub along one

   edge and mate to 9-pin de-sub of your choice. The board

   is supported at one end on the mating connector. The other

   end with a screw and spacer. Alternatively, one could

   downsize the d-sub connectors like I did here



    http://www.aeroelectric.com/articles/macservo/macservo.html



   . . . and finish off the installation with a simple, over-all

   cover of heat shrink where the relay assembly is simply tied

   to a wire bundle.



   In this instance, I think I'd solder the relay to the board

   as opposed to setting it in a socket. This process would

   yield a very compact relay assembly with robust construction,

   very low assembly time and stone simple (d-sub) interface

   to your radio. 



 

 

        Bob . . .

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messydeer

Joined: 13 Feb 2006
Posts: 214
Location: Bellingham, WA

Posted: Tue Nov 29, 2011 9:05 am Post subject: Re: PTT Y adapter for RST intercom

Thanks, Bob and Joe 



I've ordered the relay and continuous bus perfboard. I'll post some pics when I get it assembled.



I also was wondering about the power supply. I'll wire the a/c 12v supply to the wire connected to the BI terminal on the intercom circuit board. There is also an option to add a 9v battery for backup, connected to the BO terminal. I have a 1.2 Ah 12v battery that is used for my EFIS backup supply and wonder if I could wire this to the BO terminal in place of the 9v. Would I need a resistor between my 12v backup battery and the BO terminal, to drop it down to 9v? If so, how do I figure the size?



How would I know the intercom is drawing current from the main 12v supply (BI) and not the backup (BO)? Even though the small 12v backup battery gets recharged by the main a/c 12v supply, seems I'd want the a/c 12v supply to provide power for the intercom.

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Dan

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