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Problems Soldering DB-25 Connectors
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art(at)zemon.name
Guest

Posted: Sun Sep 25, 2016 5:28 am Post subject: Problems Soldering DB-25 Connectors

On Sun, Sep 25, 2016 at 4:07 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 05:44 PM 9/24/2016, you wrote:



 

  	  Quote: 	
		  On Sat, Sep 24, 2016 at 2:46 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:

 	
  On Fri, Sep 23, 2016 at 9:29 AM, Efraim Otero <efraim.otero(at)gmail.com (efraim.otero(at)gmail.com) > wrote:

   Art:

  Please send pictures so us newbies can compareâ€¦ thanks for sharing!!



  



  Efraim,



  Your wish is my command 



  



 One more photo. I disassembled and reassembled the first connector that I did (more than a week ago). I am much happier with this iteration:



 [img]cid:.0[/img]



 These wires are for the pitot tube heater. It draws 12 amps so I am using three pins each for power, plus one pin for the status lamp. These three 20 AWG pigtails join to 12 AWG wire which runs the length of the wing.

 Â  These joints look good. I would use 22AWG "ballast

 Â  resistor" pigtails. Here you are actually using

 Â  the wire as a resistor . . . the larger the better

 Â  from the standpoint of sharing loads across an

 Â  array of pins. Also, be aware that the legacy

 Â  heated pitot tubes have a strong temperature

 Â  coefficient. A typical pitot heater for a Beechejt

 Â  is 1.5 ohms at 0C . . . a time when the tube is

 Â  likely to be turned on. 28V/1.5 ohms is 18A start

 Â  up current. When the heater gets to 100C (typical

 Â  high altitude condition) it goes to 2.2 ohms

 Â  for 12.7A running current. 14v probes behave similarly

 Â  at about 2x the current.



 Â  What kind of probe are we talking about?



 Â  If you've lots of unused pins in this connector,

 Â  it wouldn't hurt to use 5 or 6 pins per path

 Â  and I'd certainly drop to 22AWG ballast wires.

 Â  Another thing to consider for the solder-cup

 Â  connector is the form of the female pins in

 Â  the connector . . . not quite as robust and

 Â  uniform their crimp style cousins . . . so

 Â  extra pins if available wouldn't hurt a thing.



 Â  The work we did at Beech was entirely with

 Â  crimped pins. I'm not suggesting that your

 Â  design goals cannot be met with this connector,

 Â  just that I have no experience with the parallel

 Â  pins in the commercial connectors so if there

 Â  are unused pins in the connector, bringing 

 Â  them into harness with the three already in

 Â  service is not a bad thing to consider.



 Â  The extra wire is a 'sense' wire? What does

 Â  it do for you?



  	


Bob,

I'm glad that those connections look better. The other ones that you criticized were my first two. I'll go back and rework them.

I am planning a Dynon heated pitot tube. Here is my wiring diagram, including the warning lamp:

â€‹

Â pitot.pdf

â€‹Dynon says that that lamp will illuminate if the heater fails.

I have plenty of spare pins in the connector. See my connector "diagram"

â€‹

Â wing root connectors.pdf

â€‹



Dynon says 11-12 A for the heater so I planned on 3 pins (at) 5 A per pin.

I'll have to buy some more 22 AWG wire if I am going to switch the ballast wires. Do you see any reason why I cannot buy 22 AWG wire locally (which won't be tefzel insulated) instead of mail ordering a small amount of tefzel wire? I can't think of any reason to prefer one insulation material over another for this application.

Cheers,

Â  Â  -- Art Z.

-- 

http://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 25, 2016 11:03 am Post subject: Problems Soldering DB-25 Connectors

 	  Quote: 	
		  

 Bob,



 I am using a Weller WES51. I have been setting it at 650 when butt splicing wires and bumped up to 700 degrees for the DB-25 pins. I can certainly try something hotter. I was worried about damaging the connector.Â 	


   700 is fine



 

  	  Quote: 	
		  I have two tips for the iron, the one that came with it and an extra narrow tip that I also bought. I find that extra narrow tip easier to control when working on the DB-25 pins but it doesn't transfer heat as well.



 I am using Kester 60/40 solder.Â 	


   Okay . . . you're 95% of the way there.

   All that's left is to refine your technique.



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 25, 2016 12:06 pm Post subject: Problems Soldering DB-25 Connectors

 	  Quote: 	
		  I'll have to buy some more 22 AWG wire if I am going to switch the ballast wires. Do you see any reason why I cannot buy 22 AWG wire locally (which won't be tefzel insulated) instead of mail ordering a small amount of tefzel wire? I can't think of any reason to prefer one insulation material over another for this application. 	


    I've packaged up enough 22AWG tefzel for this

    task. You may have it Tues, Wed for sure.



    I'd not kept track of Dynon's product line. Looks

    like their pitot tube is electronically controlled

    using a technique I proposed to Beech upteen years

    ago you duty cycle switch power to the heater

    (except that the OFF current is regulated to some

    very low value and accurately known). You measure

    voltage across the heater during off-time and

    you can deduce the heater's present temperature.



    I did a bunch of studies on pitot tubes used on

    the Beechjet during an analysis of loss of airspeed

    events. Turns out that these things are really

    easy to regulate by this methodology. I'm guessing

    that Dynon has exploited the smart controller's

    software to include soft-start during warm-up.

    Hence, extra-robust wiring for inrush mitigation

    is not necessary. But better ballasting of the

    pins . . . and adding some to the mix is  not

    a bad idea.



 

 

   Bob . . .

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efraim.otero(at)gmail.com
Guest

Posted: Mon Sep 26, 2016 11:03 am Post subject: Problems Soldering DB-25 Connectors

Thanks!! I got a lot to learn!! 	  Quote: 	
		  On Sep 24, 2016, at 5:44 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:

On Sat, Sep 24, 2016 at 2:46 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote: 	  Quote: 	
		  On Fri, Sep 23, 2016 at 9:29 AM, Efraim Otero <efraim.otero(at)gmail.com (efraim.otero(at)gmail.com)> wrote: 	  Quote: 	
		  Art:Please send pictures so us newbies can compareâ€¦ thanks for sharing!!



	


Efraim,



Your wish is my command 



	


One more photo. I disassembled and reassembled the first connector that I did (more than a week ago). I am much happier with this iteration:



<IMG_20160924_164542.jpg>These wires are for the pitot tube heater. It draws 12 amps so I am using three pins each for power, plus one pin for the status lamp. These three 20 AWG pigtails join to 12 AWG wire which runs the length of the wing.



Cheers,

    -- Art Z.



-- http://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

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ransman

Joined: 08 Aug 2008
Posts: 8
Location: Sweden

Posted: Mon Sep 26, 2016 11:22 am Post subject: Problems Soldering DB-25 Connectors

I found a good old method here:

https://www.youtube.com/watch?v=_GLeCt_u3U8



2016-09-22 2:33 GMT+02:00 Art Zemon <art(at)zemon.name (art(at)zemon.name)>:

 	  Quote: 	
		  Folks,



I am trying to solder 20 gauge wire into DB-25 connectors and having a tough time. The conductors just barely fit into the cups on the backs of the pins when everything is "dry," before tinning. After I tin either one, pin or wire, I cannot get all of the conductors into the cup. I end up with something like this:

[img]cid:ii_itdlrj9b0_1574f4d7e91899df[/img]



I'm afraid that those are not acceptable. What do you think?

If they are not acceptable, what is the solution? Can I trim a few conductors away so that the remainder will slip into the cup? Or should I just give up and switch to crimp pins? Or what?

Thanks,

Â  Â  -- Art Z.



-- 

http://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

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