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D-Sub and other small connections

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messydeer

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

Posted: Sat Apr 23, 2011 11:28 am Post subject: D-Sub and other small connections

Hi!



 I'm a few to several months away from completing my Sonex. I have all of the wiring that goes through the firewall already installed, including my MGL Enigma. I got a used Collins TDR-950 transponder a week or so ago and now need to buy and install a radio, ELT and the audio. 



The transponder came only with the bare plastic 15 position single row card edge connector housing. I understand I'd need 15 card edge contacts to crimp or solder, then slide them into this housing. I'll need to connect the other end of most of the wires to a 9-pin male D-Sub connector. The MGL V10 (or V6) radio would also use a 9-pin D-sub connector. And even if the ELT and any audio devices use those connections, there still wouldn't be that many of them. So I am considering soldering all the connections instead of crimping. I feel fairly comfortable with soldering and wouldn't have to buy a $30-40 crimp tool. I've read that soldering underneath the panel isn't fun, which could be needed for any changes made later. Seems I'd be able to pull both ends of the wires out and do this out of the plane. Anything else I'd need to consider?



There don't seem to be any solder cup card edge contacts at digikey, unless I want to buy 5,000 of them.  I'd just crimp the 15 wires with the open barrel edge contacts with needle nose pliers, right?



As far as the D-Sub connector, is there an advantage to using a plastic hood to cover the end? Seems some heatshrink would make for a good strain relief fitting.



Any comments appreciated. Below is a pic of the card edge contact at digikey.

card edge contact.jpg

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_________________
Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 24, 2011 10:50 am Post subject: D-Sub and other small connections

I feel fairly comfortable with soldering and wouldn't have to buy a 

$30-40 crimp tool. I've read that soldering underneath the panel 

isn't fun, which could be needed for any changes made later. Seems 

I'd be able to pull both ends of the wires out and do this out of the 

plane. Anything else I'd need to consider?



    Soldered d-subs can be most adequate to the

    task . . . but except for those that go to

    etched circuit boards, I've not soldered one

    in decades. I would think that you could do

    all of your harness work out of the airplane.

There don't seem to be any solder cup card edge contacts at digikey, 

unless I want to buy 5,000 of them.  I'd just crimp the 15 wires with 

the open barrel edge contacts with needle nose pliers, right?



   Please don't. The b-crimp tools are pretty specific

   in their design and function for getting a good grip

   on the wires. See:



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

As far as the D-Sub connector, is there an advantage to using a 

plastic hood to cover the end? Seems some heatshrink would make for a 

good strain relief fitting.



   Actually, heat shrink is only a marginal strain

   relief because it too is flexible. Hoods are

   always a good idea unless the bundle is

   to be supported by other means within a few

   inches of connector.

Any comments appreciated. Below is a pic of the card edge contact at digikey.



   Why not get the better tools, finish the job with

   a higher degree of confidence and then sell the

   tools? There are probably folks here on the List

   that would take them off your hands for $10 less

   than you paid for them . . . which means that you

   get to 'rent' the real-deal for $10 a shot.



   The cost of using better tools and processes

   will seem insignificant compared to the $time$

   it will take to find a pin that has become

   detached AFTER you've installed it.



   At this time I am struggling with the installation

   of a new radio in my truck . . . normally a simple

   cut-out-the-old-connector-splice-in-a-new-connector

   endeavor. But an intermittent pin in one of two

   connectors in series has caused me to cut out a

   perfectly good connector and splice around it

   before zeroing in on a bad pin in a NEW connector

   that mates with the back of the radio.



   Now, if I'd paid $30 extra for the radio and had

   Best Buy install it, I would have save about 5 hours,

   two weeks delay and lots of cursing and crying out

   in the darkness.



   It goes to the interesting question of "when does

   the bargain cease to be a bargain?" The numbers of

   folk who have regretted using the right tool is

   probably zero. The folks who have regretted not using

   the right tool are . . . well . . .

   Bob . . .

messydeer

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

Posted: Sun Apr 24, 2011 11:56 am Post subject: Re: D-Sub and other small connections

Thanks, Bob 



 	  Quote: 	
		  ...when does the bargain cease to be a bargain? 	




I'm certainly guilty of spending hours looking to save a few dollars. How much is my time worth? More than that...or it should be. 



Yet, I don't have an open barrel crimp tool. These may be the only 15 open barrel contacts I'd crimp, all the others being d-sub. I see that Eclipse makes an open barrel crimper, 300-035, which goes for $15-20. I'd be okay with that sitting around in my tool box for a decade before using it again, or like you suggest, passing it on to another builder. The other option would be to cutoff the wings of the contact and just solder it to the wire. Wouldn't this work? Granted, if I were to do 100 of them, it wouldn't be worth the time.



Also, I've seen on Frys.com that they have very cheap d-sub stuff made by Pan Pacific. Is this fit to use, or would it be better to stick with the digikey suppliers?

_________________
Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 24, 2011 2:54 pm Post subject: D-Sub and other small connections

 	  Quote: 	
		    Wouldn't this work?


	


   I have no way to assess your skill set nor

   the outcome of using any particular product

   outside its design goals without having

   personally observed and considered the results . . .

 	  Quote: 	
		    Granted, if I were to do 100 of them, it wouldn't be worth the time.


	


   Your call my friend . . .



 	  Quote: 	
		  Also, I've seen on Frys.com that they have very cheap d-sub stuff 

made by Pan Pacific. Is this fit to use, or would it be better to 

stick with the digikey suppliers?


	


   How about B&C or Steinair?

   Bob . . .

etienne.phillips(at)gmail
Guest

Posted: Sun Apr 24, 2011 4:12 pm Post subject: D-Sub and other small connections

On 23 Apr 2011, at 9:28 PM, messydeer wrote:



 	  Quote: 	
		   I've read that soldering underneath the panel isn't fun, which could be needed for any changes made later. 


	


Hi Dan



Having spent in excess of 100 hours on my back in the front of my Citabria soldering thin wires into small places, I can certainly add my voice to those who suggest finding another solution. I am more comfortable soldering than crimping for a variety of reasons, so your suggestion for making sure both ends of a wire can come out would have helped me considerably. My main problem is that nearly every instrument in my aeroplane is connected to everything other instrument, so the harness would have to come out in one massive loom, but the routing of the wires has formed a net around the supports for the panel. With more planning I could have avoided that though. 



I'd still suggest being able to get the harness out, as crimping (even with the best tools available) in a cramped space on your back in the dark is probably only slightly more fun than soldering, which in turn is only slightly better than getting teeth pulled.



My 2c...

Etienne

messydeer

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

Posted: Mon Apr 25, 2011 6:48 am Post subject: Re: D-Sub and other small connections

Thanks, guys 



I've used both B&C and Steinair before and would prefer to deal with either of them, but they don't have the parts I'd need. I may see how soldering the 'crimp' card edge contacts and if it doesn't work, switch to crimping.



Etienne, it sounds like both crimping and soldering under the panel is a pain, but you would still choose soldering if you were to do it over again, assuming you'd NOT be able to get the wires out?



Besides this transponder, I'll be getting and installing a COM radio, headset wiring, and an ELT. After flying, I may install wingtip lights. Other than this, all the wiring is already installed, including that for the EFIS. With any luck I hope to not have to pull out a 'massive loom', since the avionics would be last in, first out.

_________________
Dan

etienne.phillips(at)gmail
Guest

Posted: Mon Apr 25, 2011 3:35 pm Post subject: D-Sub and other small connections

On 25 Apr 2011, at 4:49 PM, messydeer wrote:



 	  Quote: 	
		  Etienne, it sounds like both crimping and soldering under the panel is a pain, but you would still choose soldering if you were to do it over again, assuming you'd NOT be able to get the wires out?

	




Yes... However, that's driven by some fairly unique factors. I've been soldering almost daily since I was 6, and getting hold of decent machined crimp pins for D-Subs are prohibitively expensive from here in South Africa. I tried the cheap folded sheet pins, and they are horrendous! My final choice was the solder-cup D-Subs, with heat-shrink over each wire and a housing over the whole plug, supporting the wires in a nice bundle. An entire 15-pin solder-cup D-Sub assembly is cheaper than a single machined crimp pin here, and that's when ordering hundreds of pins at a go, and excluding the cost of the required tooling! A point to add is that the MGL V10 radio is supplied with a solder-cup plug.

If I were to do it over, I would still use the solder-cup d-subs, but I'd make sure I could get the harness out. As it stands, I am able to remove each instrument without any difficulty. Bear in mind too that significant effort went into labelling each wire, and checking that it was soldered correctly. So different choices for different people. Most of the arguments I've heard for crimped pins (aside from the repeatability for unskilled labour) revolves around being able to shuffle the pins around. If the harness is made correctly the first time, the amount of shuffling that needs to be done is minimal in most cases. 

The next consideration is the stiffening of the wire (bad for vibration tolerance) around a soldered joint due to the solder wicking up into the strands of the wire. Bob can comment specifically on this, but my understanding is that if the wire is supported in the D-Sub housing, there should be no additional concern over crimped pins in this regard.

In my aircraft, I can lose the entire electrical system with no discomfort. I am day VFR only pilot, and have steam backups for the airspeed, altimeter and engine indications. I also have a handheld radio, no flaps, manual trim, fixed undercarriage, and twin magnetos. So if any wire were to come loose, the heatshrink should stop it from shorting out, but if it did then at worst it would pop a circuit breaker, and I'd sort it out on the ground.

My solution to the transponder problem, if it were me, would be to solder pigtails directly onto the card, leading to a 15- or 25-pin D-Sub. This would eliminate those awful low-pressure card-edge connectors that are nigh impossible to find now days. I would use a flexible epoxy to cover the soldered joints onto the card to offer some form of vibration relief on the hardened wire. This might mean modifying the tray, but it would yield an easily disconnectable instrument. This solution may very well have hidden dragons though, so I offer it for peer review!

Thanks

Etienne

 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 25, 2011 4:39 pm Post subject: D-Sub and other small connections

If I were to do it over, I would still use the solder-cup d-subs, but 

I'd make sure I could get the harness out. As it stands, I am able to 

remove each instrument without any difficulty.



    In the heavy-iron factories, we endeavor to make each

    instrument harness long enough that the connectors can

    be mated up before the instrument is stuck in the hole

    and mounted. There is NO way you lay on your back and

    work behind the panel on a King Air or Beechjet.



  Bear in mind too that significant effort went into labelling each 

wire, and checking that it was soldered correctly. So different 

choices for different people. Most of the arguments I've heard for 

crimped pins (aside from the repeatability for unskilled labour) 

revolves around being able to shuffle the pins around. If the harness 

is made correctly the first time, the amount of shuffling that needs 

to be done is minimal in most cases.



     With reasonable care, the solder-cup connector

     is perfectly suitable component. I published this

     installation comic-book some years ago . . .



http://www.aeroelectric.com/articles/dsubs/d_solder.html



The next consideration is the stiffening of the wire (bad for 

vibration tolerance) around a soldered joint due to the solder 

wicking up into the strands of the wire. Bob can comment specifically 

on this, but my understanding is that if the wire is supported in the 

D-Sub housing, there should be no additional concern over crimped 

pins in this regard.



     Behind-the-joints support on d-subs is necessary

     whether the pins are soldered or crimped. Neither

     pin technology offers insulation support behind

     the pin-to-wire interface. The wire is just as

     'solid' inside a crimped pin as it is on a soldered

     pin. So use the hoods . . . or pot the back side

     like . . .



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



My solution to the transponder problem, if it were me, would be to 

solder pigtails directly onto the card, leading to a 15- or 25-pin 

D-Sub. This would eliminate those awful low-pressure card-edge 

connectors that are nigh impossible to find now days. I would use a 

flexible epoxy to cover the soldered joints onto the card to offer 

some form of vibration relief on the hardened wire. This might mean 

modifying the tray, but it would yield an easily disconnectable 

instrument. This solution may very well have hidden dragons though, 

so I offer it for peer review!



    Been there, done that. Works good and lasts a long

    time. You'll want to fabricate a bench test harness

    to send along with your radio if it has to go to the

    shop so the tech can power it up.



   Bob . . .

   Bob . . .

ceengland(at)bellsouth.ne
Guest

Posted: Mon Apr 25, 2011 4:41 pm Post subject: D-Sub and other small connections

On 4/25/2011 6:28 PM, Etienne Phillips wrote:      	  Quote: 	
		  

                On 25 Apr 2011, at 4:49 PM, messydeer wrote:

         

          	  Quote: 	
		             Etienne, it sounds like both crimping and soldering under             the panel is a pain, but you would still choose soldering if             you were to do it over again, assuming you'd NOT be able to             get the wires out?

         	
         

       

       Yes... However, that's driven by some fairly unique factors.         I've been soldering almost daily since I was 6, and getting hold         of decent machined crimp pins for D-Subs are prohibitively         expensive from here in South Africa. I tried the cheap folded         sheet pins, and they are horrendous! My final choice was the         solder-cup D-Subs, with heat-shrink over each wire and a housing         over the whole plug, supporting the wires in a nice bundle. An         entire 15-pin solder-cup D-Sub assembly is cheaper than a single         machined crimp pin here, and that's when ordering hundreds of         pins at a go, and excluding the cost of the required tooling! A         point to add is that the MGL V10 radio is supplied with a         solder-cup plug.

       

       

       If I were to do it over, I would still use the solder-cup         d-subs, but I'd make sure I could get the harness out. As it         stands, I am able to remove each instrument without any         difficulty. Bear in mind too that significant effort went into         labelling each wire, and checking that it was soldered         correctly. So different choices for different people. Most of         the arguments I've heard for crimped pins (aside from         the repeatability for unskilled labour) revolves around being         able to shuffle the pins around. If the harness is made         correctly the first time, the amount of shuffling that needs to         be done is minimal in most cases. 

       

       

       The next consideration is the stiffening of the wire (bad for         vibration tolerance) around a soldered joint due to the solder         wicking up into the strands of the wire. Bob can comment         specifically on this, but my understanding is that if the wire         is supported in the D-Sub housing, there should be no additional         concern over crimped pins in this regard.

       

       

       In my aircraft, I can lose the entire electrical system with         no discomfort. I am day VFR only pilot, and have steam backups         for the airspeed, altimeter and engine indications. I also have         a handheld radio, no flaps, manual trim, fixed undercarriage,         and twin magnetos. So if any wire were to come loose, the         heatshrink should stop it from shorting out, but if it did then         at worst it would pop a circuit breaker, and I'd sort it out on         the ground.

       

       

       My solution to the transponder problem, if it were me, would         be to solder pigtails directly onto the card, leading to a 15-         or 25-pin D-Sub. This would eliminate those awful low-pressure         card-edge connectors that are nigh impossible to find now days.         I would use a flexible epoxy to cover the soldered joints onto         the card to offer some form of vibration relief on the hardened         wire. This might mean modifying the tray, but it would yield an         easily disconnectable instrument. This solution may very well         have hidden dragons though, so I offer it for peer review!

       

       

       Thanks

       Etienne

       

     	
     I've successfully soldered quite a few of the edge type pins     pictured in an earlier email; I just manually folded the shorter     wings with needle nose pliers, soldered, then manually wrapped the     longer wings. Not a lot of fun, but very 'do-able'.  However,     Etienne's solution makes even more sense, as long as warranty isn't     an issue.

     

     By paying the price of an extra few ounces & some careful     planning, you can avoid diving under the panel for future soldering     or crimping sessions. Just make service loops & routing so the     connectors can be brought out into the cockpit, or even out over the     wing for soldering sessions.

     

     Charlie

      [quote][b]

messydeer

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

Posted: Tue Apr 26, 2011 6:52 am Post subject: Re: D-Sub and other small connections

 	  Quote: 	
		  My solution to the transponder problem, if it were me, would be to solder pigtails directly onto the card, leading to a 15- or 25-pin D-Sub. 	




I think I'll have that as plan B, if I can't get the edge contacts to work right.

_________________
Dan

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