D-Sub connectors

[skippydiesel]

Just thought I would share my recent experience on this topic;

 

My son & I (mostly him) have been busy wiring our new Sonex Dynon/Trig system.

 

Much of the heavy lifting has been reduced by having pre wired cables (plug each end). This has a down side - lots of surplus length and "coils"

 

I have been taught, that coils of wire/cable are a bad thing in any application (except house wiring). This has lead to the need to reduce cable lengths for both a neater (more professional) look and minimise the potential for electro magnetic interference from powered cable  coils.

 

The offending cables have a female D-Sub connecter at each end, with two rows of connectors , totaling 9 pins.

 

My instinct was to purchase new female pins (22 in all , including a few spares for stuff ups) plus a pin removal/installation tool (I already have the 4 way crimper).

 

After about 4-5 hrs on the phone, talking with various vendors tech staff & RFguy, I discovered people no longer reuse the casings on D-Sub plugs - they just purchase a plug kit (with all the bits). In large part this is because purchasing small quantities of connector pins is prohibitively costly  when compared to  just acquiring a kit to do the job.

 

So! I could have purchased a kit from several Australian generic parts suppliers  but chose instead to purchase from Dynon. Dynon's charge was about double the cheapest generic but about half way for the rest of the offerings - so reasonably competitive.

 

From my perception, Dynon product has the edge;  being guaranteed compatible with their systems and available immediately (the generic suppliers get stuff from overseas on a just in time delivery system).

 

The take home message - dont wast time researching all the specifications you will need to purchase the correct D-Sub pin connectors - just buy a kit from the instrument supplier.

 

Looking forward to spending a few pleasant hours shortening cables & fitting  new D-Sub plugs

[IBob]

That's good input, Skippy.

I will be installing ADSB in the coming months, was looking at making up my own harness, I have the correct crimp tool but the crimp pins/sockets seem to be hen's teeth.

You're saying you got the crimp plug kits from Dynon?

Or are you saying you just bought the appropriate length harness from Dynon (the harnesses for their gear do seem to be reasonably priced, and available in various lengths).

[skippydiesel]

12 minutes ago, IBob said:

........................................................

You're saying you got the crimp plug kits from Dynon?

Or are you saying you just bought the appropriate length harness from Dynon (the harnesses for their gear do seem to be reasonably priced, and available in various lengths).

You can purchase pre wired harness in a range of lengths from Dynon - not cheap.

 

That's what the original builder of my Sonex has done. Unfortunately this has lead to over long cable lengths and coiling to "tidy away".

 

So I have purchased plug kits from Dynon. By doing this,  I dont have to stress (anymore) over finding just the correct type of pin connector (there are so many options) and it turns out the plug kit is just about the same price (may even be slightly cheaper) as purchasing just the pins alone.

 

I will carefully measure/size the existing overlong cables taking into account routing AND strain relief, cut,& install new plug kit at the correct length (without coils& unnecessary loops. By doing this I hope for a much neater, lighter and less lily to generate electromagnetic interference (esp radio)

[IBob]

Gotit........thanks.

[skippydiesel]

FYI 

 

The Dynon plug kit is about $12/plug,

 

Element 14,   P No. 8E09FG-kIT, about $6 - (Dynon  equivalent)

 

However you can go up market with;

 

Element 14, P No 749806 and pay $28.44 /plug - gold plated pins

[kgwilson]

A D-Sub is a D-Sub. It is a standard fitting. They cost bugger all from Jcar. Even a gold plated one is less than $10.00. The standard male or female with solder tags costs a dollar or something & the plastic case about the same. I made all my own harnesses for my Dynon & I've never had a problem. I had about 20 metres of shielded 9 core computer cable in the shed so just cut it to length. You just need a good fine tip soldering iron, fine fluxed solder, & some fine heat shrink for each core to cover the joint including the tag.

[skippydiesel]

1 hour ago, kgwilson said:

A D-Sub is a D-Sub. It is a standard fitting. They cost bugger all from Jcar. Even a gold plated one is less than $10.00. The standard male or female with solder tags costs a dollar or something & the plastic case about the same. I made all my own harnesses for my Dynon & I've never had a problem. I had about 20 metres of shielded 9 core computer cable in the shed so just cut it to length. You just need a good fine tip soldering iron, fine fluxed solder, & some fine heat shrink for each core to cover the joint including the tag.

Cant comment with any authority, however my extraordinary limited experience (5 hrs research) would suggest otherwise, with many pin dimensional, material  & attachment (to wire)  variations (check out Element 14 web site)- hence my final retreat to the safety of the  known (Dynon).

 

Jaycar (been there)  is spectacularly lacking is product specifications - as an expert you are no doubt correct, however I could make no certain/informed decision on their products, nor get help from their staff.

 

 I am not a fan of soldered electrical joints, in high vibration or potentially humid environments, much preferring crimped joints (very occasionally soldered & crimped).

 

The cables, I will shorten, are all aircraft grade, "twisted" shielded, multi core cable, as specified by Dynon.

 

This is after all an aircraft,  so without a background/experience in electronics, I go with the makers specifications/instructions - ground based machine? different matter entirely..

[kgwilson]

Tefzel MIL-W-22759/16 22 AWG wire is recommended by Dynon but standard computer cable does an equally good job. The only difference is the tefzel insulation which has a higher melt point but it is not as flexible. Well soldered joints work equally as well & there is no issue of a pin coming loose or being pushed out. With a soldered joint the weak point is where the solder and wire merge so this is why the wire is heat shrunk well beyond the join & then all cores (wires) are clamped inside the connector casing. My D6 has 2 x D-25 pin connectors between the unit and the remote compass as well as the D-9 for computer connections. The cable is only 250mm long as the remote compass is mounted behind the panel away from everything and under the panel top. Just above this on the centre canopy front frame bar is the liquid filled compass.

 

It is critical to make sure that the remote compass is as far away as possible from current carrying wires or anything magnetic and is mounted at the same pitch, roll & yaw as the panel mounted unit.

 

 

[Jabiru7252]

Gee, I see an opportunity here. Maybe I'll make up the cables, length given by the customer and flog them. I must have wired 10 million 25pin, 15pin and 9pin connectors in my life. Mainly for computer use, not aviation, not that it matters.

[kgwilson]

It doesn't matter. By the time any computer wires get to the point of melting you are already cooked. Aviation manufacturers provide plenty of spin to try & make you buy their over priced products.

[Yenn]

Isn't the reason for aviation grade wire to reduce the noxious gases emitted if there is a fire.

By all means use any old wire and it will probably be OK until you get a short and a fire. then you will want Tefzel.

[Geoff_H]

7 hours ago, kgwilson said:

It doesn't matter. By the time any computer wires get to the point of melting you are already cooked. Aviation manufacturers provide plenty of spin to try & make you buy their over priced products.

It is not the wires melting that the current rating is based on it is the maximum temperature that the insulation can stand.  With the Tefzel wire (a Teflon like product with less lethal gasses given off in a fire), you can use a smaller gauge wire, a weight reduction.  Digital signals don't require a high current, not even the power supplies, but you never know what will go wrong.  Murphy was an optimist!!

I would never again solder, I had so much trouble, even with heat shrink, then I was told to crimp....now I always crimp.

Only use non oxidation gold connection.  In my younger days we carried ink erasers to clean dirty signal connections.  Gold was a saviour.  No good getting a failed digital signal for lack of quality connect systems.

[skippydiesel]

On 03/01/2022 at 3:42 PM, Geoff_H said:

I.....................................................

I would never again solder, I had so much trouble, even with heat shrink, then I was told to crimp....now I always crimp.

Only use non oxidation gold connection.  In my younger days we carried ink erasers to clean dirty signal connections.  Gold was a saviour.  No good getting a failed digital signal for lack of quality connect systems.

I learnt how "fragile" solder was when I did a stint on a fisheries reserch station - the combination of high humidity,salty air, electrical current & vibration pretty much made soldering a non starter.

 

"Only use non oxidation gold connection" - when I was researching on "how to shorten my cables" I came across different grades/types of gold treatment, as well as plain brass "pins".  The options (size/materials/gold treatments) all became too confusing hence my return to Dynon. Dynon informed me that they use simple brass pin contacts.

 

[RFguy]

Solder is not all bad. Compared to the stuff most people are exposed to, there are many exotic and excellent electrical solders.  Some research has to be usually done or known about the plating of the surface you are going onto. There are combinations that are unwise !

 

But, if you can get a strain releived crimp or swage connection, super. 

 

BTW Sean, gold is fine, depends how many cycles it is subjected to, or vibration. Gold flash is good for a low cycle, stationary  or well held connector applications, otherwise go gold plating.

 

 

[skippydiesel]

2 hours ago, RFguy said:

Solder is not all bad. Compared to the stuff most people are exposed to, there are many exotic and excellent electrical solders.  Some research has to be usually done or known about the plating of the surface you are going onto. There are combinations that are unwise !

 

But, if you can get a strain releived crimp or swage connection, super. 

 

BTW Sean, gold is fine, depends how many cycles it is subjected to, or vibration. Gold flash is good for a low cycle, stationary  or well held connector applications, otherwise go gold plating.

 

 

Job done - 2 cables shortened - tested and work just fine. Not hard, just fiddly. Very satisfying to see the  coils gone and a much neater behind panel look.

[Geoff_H]

Yesterday I had my latest encounter with soldered joints failing.  A classic mini that had an upgrade to a solid state fuel pump, one we often see in aircraft.  The short leads from the pump had an extension soldered to extend their length to a plug.  Sitting near the rear suspension the pump even has its own vibration isolation mount.  The joints (positive and negative) had heatshrink around them.  Finally failed several years after installation. Unfortunately 200km from home.  I am just glad it was not an aircraft.  A motor mechanic soldered a new pump in, he did not realise what the failure really was.  The owner and I have a date to replace the soldered joints with crimped ones.  With a professional crimp tool!

[skippydiesel]

1 hour ago, Geoff_H said:

......................  With a professional crimp tool!

You probably know - the correct crimping tools come in either AWG sizes or additional parts to accommodate different wire /terminal dimensions. The best deal that I found was Toledo at about  $70 (from memory they do about 3-4 sizes)- still expensive for tow cables but just a tad cheaper than the & thousand plus dollars for a MIL Spec pair.

[IBob]

Digging down to what fails:
My understanding (and i'm happy to be corrected) is that with soldered joints or terminations of multi-strand wire, the strands are welded together by the solder for short distance and so unable to flex. Which concentrates any flex at the point where the solder ends, and the strands are free to move. This then becomes the potential weak point.

However:

In the case of the D-sub connector, the wires are held by an internal clamp before leaving the connector. And if this clamping is done correctly, with a small amount of slack in the individual wires, there should be no flexing at this potential weak point.

Stripping, soldering and final assembly would still need to be carried out carefully.

[facthunter]

Soldering should only be done with resin cored electrical solder and any tinning of the soldering "iron" (it's actually pure copper) should be followed by a quick dipping of the end in clean water so no killed spirits or active flux gets into the equation.. In a corrosive environment ie Marine or coastal, exposed bunched copper fine strand wires will corrode. Green corrosion, Called "verdigris"  happens in old coils Stators and transformers where the "shellac" has died. Also happens near battery terminals where sulphuric acid seeps..

[spacesailor]

Nothing Seems to stop the green corrosion! .

BUT

fully tinned copper wire.

The soldered joint can be tapred from the full solder joint, down to the last couple of wires.

Then a epoxy coat , shrink wraped before setting &  finely,  a good thick coating of lanolin grease.

And fastened correctly to stop vibration. 

spacesailor

 

[Geoff_H]

On 15/01/2022 at 7:57 PM, spacesailor said:

Nothing Seems to stop the green corrosion! .

A properly done crimp does.

[spacesailor]

Can l give you a long length of wire !.

Proberly  4 metres green anywere you cut it, was over 15 metres but tried very hard to find that elusive good end to crimp another terminal on.

Sea water travels uphill to ruin copper .

 Even up on roofs that copper will be GREEN.

spacesailor

 

[onetrack]

Properly installed heatshrink around a connector will prevent the ingress of moisture, dust, salt, acid fumes, and other damaging chemicals in the air, that cause verdigris on copper. However, there is a problem with using PVC-coated wiring, where a plasticiser has been added to the PVC to improve the production process.

 

The plasticiser is a pthalate, which when it breaks down with the high temperatures that some wiring can encounter, releases hydrochloric acid, which then attacks the copper wire and creates verdigris.

The plasticiser in the PVC coating of copper wire was common in the 1960's and 1970's, but is less common today - except for the cheaper grades of PVC-coated wiring.

 

As a result, if you're not using Tefzel wiring in your aircraft, and you have common automotive wiring, it's entirely possible you're going to encounter verdigris-affected copper wiring at some stage, even if it has been sealed with heatshrink.

 

Spacey, seawater doesn't "run uphill" on roofs to attack copper - the salt-laden moist air is driven up the roof cladding by strong winds, and accordingly finds its way under the overlapping roof cladding joints.

 

Edited January 17, 2022 by onetrack

[Geoff_H]

A properly crimped joint is a galvanic bond and will only corrode around the edges. High voltage (330/500kv)I we are crimped, often  near salt water, they  are not known to collapse from corrosion of the joints.

[RFguy]

Hey Geoff are crimps and swages the same thing at the joining level ?