DB25 Connector

tonycondon

tonycondon

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Tony
I am going to pick up a DB 25 connector for my transponder tomorrow. I've got the connector that goes to the encoder. What sort of device would you guys use for connecting the loose wires to the 25 pin connector?
 
An eighteen watt needle tipped soldering iron.

Heatsink the pins with a mini grabber or you'll melt the plastic. These are for 28 guage wires, they're quite small......
 
tonycondon said:
I am going to pick up a DB 25 connector for my transponder tomorrow. I've got the connector that goes to the encoder. What sort of device would you guys use for connecting the loose wires to the 25 pin connector?
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If its a soldered connector, that aforementioned soldering iron and a magnifying glass and a heat sink of some sort..

If its a crimp style, I use D-sub crimps... I've had better luck with the "open sided" pins that make a horseshoe crimp than I have with the barrel crimp style pins, even though I've heard people claim barrel crimps are superior

EITHER way.. solder or crimp, strain relief is EXTREMELY important if you want the connections to last.
 
I like the Crimp Style DB connectors that radio shack sells. As I recall the crimping tool is a bit expensive and you will probably eventally want a pin extractor (tool).

Crimping is a lot easier and cleaner than soldering.

Brian Case
HP16T.
 
Solder. Event he crimp connections. With the amount of vibration in a plane it has been my experience that even on a good crimp job it is only a matter of time until they fail. But solder them and it will be decades.
 
scott - not much vibration in my glider.
 
When I was in the business of soldering DB-25s, I used a soldering iron with the finest tip I could find. Use only enough heat to melt the solder and let it flow. I didn't use an explicit heatsink; I just plugged it into the mating connector. Even if the plastic melted, it hardened right back where it was, and the pin was never out of position.
 
tonycondon said:
scott - not much vibration in my glider.
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movement = vibrational modalities. If your glider never moves then yes I would agree. But if you fly it, then it moves and the modes of that movement can equal mechanical stress on the electric connections.

Lets put a few accelerometers on your glider and see what types of movements they record. I'll bet you have random and semi-periodical modes during flight.
 
Remove the pins to solder them and then insert - no plastic melt.
 
ill be connecting to the female end, if that makes a difference.
 
yea now that i look at a few more pictures of connectors it is obvious that the part where the wires connect to the connector is completely asexual.

scott i don't live in iowa anymore so im not sure that i could connect to a male connector, even if i wanted to. :)
 
mikea said:
Remove the pins to solder them and then insert - no plastic melt.
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That only works on the kind that has removable pins. Most solder-type DB-25s don't.

tonycondon said:
ill be connecting to the female end, if that makes a difference.
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Yes, it does. It means you can't easily grab the pin with something to use as a heat sink. If you've got an old IBM PC with a parallel port, you can plug the connector into that while soldering to it.
 
thanks Jay. it looks like the connectors are pretty cheap. I will probably just buy a male and female end. having the male end plugged in was recommended on some forum to help hold the pins in the right place while the plastic gets heated up. and it will be a nice heat sink like you describe.
 
A good crimp job, in such an application, is perfectly acceptable and will last just fine. Not only that -- someone not experienced with soldering would have a better chance at crimping it properly then soldering it properly.
 
Given a choice, I'd always choose the crimp-on connectors, which are then inserted into the shell. Easier to work with, and less hassle of you screw one up.

$0.02.
 
Huh- I always thought crimps were desirable for aircraft wiring because solder was more prone to vibration failure...? I do know that in the A/V world, for rides and other things that move a lot, crimps, or better yet, screw terminals are usually used whenever possible for connections.

Regarding which is easiest to do (solder or crimp'n'insert): I'm pretty good at soldering, and generally don't enjoy crimping pins (on D-subs and other small connectors). Especially if you have to remove any pins because of an error- even with an extraction tool, it's a PITA. :mad3:

BUT:
Solder or crimp, just remember your male/female pinout for D-subs... the little numbers on the block are hard to read, but the way I remember it is:

"From behind, the female looks correct". :D

In other words, with a D-sub, when you view the pins from behind the connector, the pin numbering sequence starts in the upper left corner, and you read the sequence left to right in each row (pin 1, pin 2, etc.). With a male, the layout is reversed (duh): starts in the upper right corner.
 
The stresses on the connectors in a glider are very low, especially if you have a proper strain relief on the connector. If I am using a connector in a vibration prone area I will crimp it an then touch is with a bit of solder. This way I can solder it prior to inserting the pin into the connector.

Brian
 
brcase said:
The stresses on the connectors in a glider are very low, especially if you have a proper strain relief on the connector. If I am using a connector in a vibration prone area I will crimp it an then touch is with a bit of solder. This way I can solder it prior to inserting the pin into the connector.

Brian
Click to expand...

I think you're making things worse by soldering. A proper crimp is supported by the insulation and the conductor, will make a connection that's as strong as the wire itself, and is also gas tight (won't corrode). Done properly soldering is also OK but it always requires a good strain relief near the joint as the transition from flexible to solid at the joint creates a stress riser.

Tony, I also recommend the crimp approach and if at all possible use a high quality (and calibrated) tool intended for the specific terminals used. Other crimp tools will work but with them you need to be able to tell the difference between a good and a not so good crimp, the good tools make it almost impossible to get it wrong.

If you do go the soldered route you also need to put heat shrink on each wire with the end slipped over the entire solder joint plus about a few mm of insulated wire. The suggestion to plug the connector you're soldering into a spare mate (never use the radio itself for this) is a very good idea. Without that it's all too easy to end up with one or more pins that are not parallel to the rest and that will cause a problem each time you attempt to plug in the unit. Just be aware that with some styles you can end up with the connector you're working on soldered to the mate it's plugged into (BTDT), at which point you have to start all over.

BTW another advantage of the crimped type is that if you ever need to make changes at some point in the future, it's way easier to do. Typically the existing wires from the connector go to several places in the aircraft so you can't take the thing out to a bench where it's easier to solder and therefore end up trying to solder the new wires while upside down under the panel.
 
gismo said:
I think you're making things worse by soldering. A proper crimp is supported by the insulation and the conductor, will make a connection that's as strong as the wire itself, and is also gas tight (won't corrode).
Click to expand...
Depends a lot of the design of the crimp and the quality of the crimp. Most of the type of crimps that are used for db25 connectors will support the insulation but then so will soldering the connection to the same connector and then folding the tabs of the pin over onto the insulation. But with the crimping one often uses excessive force onto the wire which will de-shape or nick the wire and create a mechanical weak point that can lead to a failure later.

gismo said:
Done properly soldering is also OK but it always requires a good strain relief near the joint as the transition from flexible to solid at the joint creates a stress riser.
Click to expand...
I agree with the strain relief as well, that is always needed regardless of the connection type. Soldering can also be an art. High Reliability soldering is something that people are trained to do. But one of the keys is to make sure the joint is hot enough. I have soldered more conenctors than I can remember and have never had a solder joint fail that I can recall. But I have seen many crimped connection fail and need replacement or repair.

gismo said:
Tony, I also recommend the crimp approach and if at all possible use a high quality (and calibrated) tool intended for the specific terminals used. Other crimp tools will work but with them you need to be able to tell the difference between a good and a not so good crimp, the good tools make it almost impossible to get it wrong.
Click to expand...
The better crimps do use the better tools. The ones that are closely calibrated and provide a symmetrical force onto the connector. But most likely the one that Tony will access to is the typical squeeze and smash type that put all of it's force in one dimension. These are the tools that are available to most hobbyists.

gismo said:
If you do go the soldered route you also need to put heat shrink on each wire with the end slipped over the entire solder joint plus about a few mm of insulated wire.
Click to expand...
If he does nto use eessive heat he may be able to get away without doing this. I would say tin the wire, then heat the connector pin, and insert the wire into the pin, maybe add a dot of solder and then remove the heat. Let cool, fold over the strain tabs and rinse and repeat on the next pin. or it could also be of a desing that the entire cable coming into the housing is strained relieved. I am not sure which type of connector Tony is using. But I do know that when I worked at KSC and Cape Canveral in the early 1980's that no crimps or wire wraps were authorized unless they were also soldered. It was due to failure in mission critical issues that this mandate was made. This was on the ground and console gear not just the vehicles which had even higher standards.



gismo said:
BTW another advantage of the crimped type is that if you ever need to make changes at some point in the future, it's way easier to do. Typically the existing wires from the connector go to several places in the aircraft so you can't take the thing out to a bench where it's easier to solder and therefore end up trying to solder the new wires while upside down under the panel.
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I am not following your reasoning on this. Whether soldered or crimped it is easy to change a pin. But I see mostly on crimped that you have to cut the pin off which could leave you short of wire had you not had any slack to begin with. Whereas soldered can just remove the pin with the application of a little heat.
 
It was 4:50 AM - where in the world is Scott? ;)
 
i picked up a crimp connector and a crimping tool at radio shack. i should've sprung for the nifty wire stripper thing but i didnt. the wire is too small for the stripper on the crimping tool. will have to make another radio shack run today. oh well there are other things i need to get anyway.
 
tonycondon said:
i should've sprung for the nifty wire stripper thing but i didnt.
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Cool we can start another electronics holy war!!

Wire stripping.

Those squeeze strippers with the blades....BAAADDD

Far too easy to nick the wire and create a mechanical weak point. The only stripper that is worth using that does not damage the wire is a heat stripper. It melts the out casing of the wire and allows you to remove it without damage to the underlying conductor.
 
Hey Scott, why don't you test out your fancy new Garmin box on an XC to Wichita, and solder the connector for Tony :D:D:D

that way it'll be done correctly:devil::devil:
 
vontresc said:
Hey Scott, why don't you test out your fancy new Garmin box on an XC to Wichita, and solder the connector for Tony :D:D:D

that way it'll be done correctly:devil::devil:
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I considered offering to do it for Tony at Estherville...price: one pizza.
 
vontresc said:
Hey Scott, why don't you test out your fancy new Garmin box on an XC to Wichita, and solder the connector for Tony :D:D:D

that way it'll be done correctly:devil::devil:
Click to expand...
Not a bad idea and a good use of GA!! :D

I used to like building cables when I was first starting out. There is a zen-nis to it.
 
Jay I am going to be in Estherville next weekend but my plate is already full, plus I'd like to have the wire done by then.
Im heading to radio shack again tonight to buy more gadgets. ill be sure to keep posted on my progress.
 
smigaldi said:
Depends a lot of the design of the crimp and the quality of the crimp. Most of the type of crimps that are used for db25 connectors will support the insulation but then so will soldering the connection to the same connector and then folding the tabs of the pin over onto the insulation. But with the crimping one often uses excessive force onto the wire which will de-shape or nick the wire and create a mechanical weak point that can lead to a failure later.
Click to expand...

Even the heat resistant insulation used in aircraft wire will retract slightly (shrink) when exposed to the heat of soldering IME. This makes it difficult (but not impossible) to crimp the insulation on a soldered joint. Also I was under the (possibly incorrect) impression that part 43 requires that you use terminals designed to be soldered if you are making soldered connections and no solderable terminals I've ever seen have any insulation support.

I agree with the strain relief as well, that is always needed regardless of the connection type. Soldering can also be an art. High Reliability soldering is something that people are trained to do. But one of the keys is to make sure the joint is hot enough. I have soldered more conenctors than I can remember and have never had a solder joint fail that I can recall. But I have seen many crimped connection fail and need replacement or repair.
Click to expand...

Properly soldered connections are certainly quite robust initially but they are far more likely to fail if exposed to vibration than crimps. And properly formed crimps shouldn't fail either. Also I would say that an untrained person is more likely to make a good crimp if they use a good tool than they are to make a good solder joint. I have a fair amount of experience with both and I've seen both fail but in virtually all cases the crimp failures were traceable to a tool problem or a careless operator. I have seen perfectly good solder joints fracture after being subject to vibration for an extended period. I do agree that if you can eliminate any motion of the wire within 1-2 cm of the joint a properly soldered connection is at least as robust as a crimp and potentially better.

The better crimps do use the better tools. The ones that are closely calibrated and provide a symmetrical force onto the connector. But most likely the one that Tony will access to is the typical squeeze and smash type that put all of it's force in one dimension. These are the tools that are available to most hobbyists.
Click to expand...
Agreed. And ironically a "hobbyist" crimper can be used to make an acceptable connection but the skill level to do so is much higher than when using a "professional" tool.

If he does nto use eessive heat he may be able to get away without doing this. I would say tin the wire, then heat the connector pin, and insert the wire into the pin, maybe add a dot of solder and then remove the heat. Let cool, fold over the strain tabs and rinse and repeat on the next pin. or it could also be of a desing that the entire cable coming into the housing is strained relieved. I am not sure which type of connector Tony is using.
Click to expand...

That will work but I'd bet even money that Tony will have trouble doing this correctly (not saying anything against Tony, just that this is not easy for someone who's not done much detailed soldering before. With your method (soldering crimp pins) there's an awfully good (bad?) chance that the pin won't fit into the connector body because the uncrimped portion is too large. Even if you crimp then solder it's likely to be too big unless the person doing the work is very good at it.

But I do know that when I worked at KSC and Cape Canveral in the early 1980's that no crimps or wire wraps were authorized unless they were also soldered. It was due to failure in mission critical issues that this mandate was made. This was on the ground and console gear not just the vehicles which had even higher standards.
Click to expand...

I think I've seen studies that disprove the benefit of soldering a crimp but NASA tends toward the belt+suspenders approach so that requirement doesn't surprise me. In any case I think you will find that the vast majority of connector terminations in GA airplanes are crimped without solder (and they work quite well).

I am not following your reasoning on this. Whether soldered or crimped it is easy to change a pin. But I see mostly on crimped that you have to cut the pin off which could leave you short of wire had you not had any slack to begin with. Whereas soldered can just remove the pin with the application of a little heat.
Click to expand...

I was referring to a DB-25 that was intended to be soldered and had no removable pins. Certainly if you make soldered connections to removable pins, crimps offer no advantage WRT changes.
 
gismo said:
Properly soldered connections are certainly quite robust initially but they are far more likely to fail if exposed to vibration than crimps. And properly formed crimps shouldn't fail either. Also I would say that an untrained person is more likely to make a good crimp if they use a good tool than they are to make a good solder joint. I have a fair amount of experience with both and I've seen both fail but in virtually all cases the crimp failures were traceable to a tool problem or a careless operator.
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I also have a good bit of experience with both. I even have my certificate from graduating form NASA High Reliability solder course.

What can be the deciding factor in crimping or soldering is based a lot on the application, the type of wire, the quality of crimping tool and the operator. But from my experience I have seen far more bad crimps than bad solder joints. This is why it is very rare that you will see any crimping on any mission critical communication cable used at the space center. You and I will have to agree to disagree.
 
smigaldi said:
I also have a good bit of experience with both. I even have my certificate from graduating form NASA High Reliability solder course.

What can be the deciding factor in crimping or soldering is based a lot on the application, the type of wire, the quality of crimping tool and the operator. But from my experience I have seen far more bad crimps than bad solder joints. This is why it is very rare that you will see any crimping on any mission critical communication cable used at the space center. You and I will have to agree to disagree.
Click to expand...
I suspect the folks at NASA soldering mission critical communication cables are probably better at soldering than Tony.
 
jesse said:
I suspect the folks at NASA soldering mission critical communication cables are probably better at soldering than Tony.
Click to expand...

I bet well-trained monkeys are better at soldering than Tony.





Sorry. :D
 
hey now thats nifty! If i screw up the crimping so bad maybe that will have to be my plan B
 
smigaldi said:
I also have a good bit of experience with both. I even have my certificate from graduating form NASA High Reliability solder course.

What can be the deciding factor in crimping or soldering is based a lot on the application, the type of wire, the quality of crimping tool and the operator. But from my experience I have seen far more bad crimps than bad solder joints. This is why it is very rare that you will see any crimping on any mission critical communication cable used at the space center. You and I will have to agree to disagree.
Click to expand...

I'm OK with that (agreeing to disagree) but I'm not certain that we actually disagree on much here. I certainly won't argue that properly implemented soldered connections aren't superior in certain applications (space vehicle/mission critical/cost no object applications do come to mind). And I certainly cannot refute that you've seen more bad crimps than bad solder joints, especially if most of the potentially bad joints were made by qualified technicians working to a defined standard of excellence. My main point was that an unskilled/untrained maker of connections with a good crimper often has a better chance of making a reliable connection than the same person with an excellent soldering iron. If you disagree with that, so be it. I won't think any less of you for your incorrect opinion:D. And perhaps I was overstating a bit about the susceptibility of soldered connections to vibration induced stress failures. I do agree that this is only true if the connection isn't properly supported which is extremely unlikely in the cases you mentioned. So I'm with you on the notion that soldering is more than adequate and even more desirable in certain circumstances as long as it's all done correctly including the design of the strain relief etc. But I'm not so certain that this is true when you're talking about DB-25s from Radio Shack soldered by Tony lying upside down underneath his panel in the dark with a blowtorch.
 
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