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Micro Molex Pins/Connectors

asw20c

Well Known Member
I spent several hours today in bright sunlight attempting to crimp those teeny tiny micro molex pins onto the teeny tiny 26 gage wires to mount in a molex connector for the elevator trim servo. I eventually was successful but not without a lot of swearing and multiple attempts. I have the BCT-1 crimping tool so that's not the issue, and eventually I got better with each pin in making the proper crimps without mangling the pin. No, the real problem was inserting the pins into the molex connector. Is there a special tool for this? It was almost impossible, and yes I did have them aligned properly for the key in each hole. God help me if I ever need to remove a pin for trouble shooting. How does one do that without destroying the pin/wire/connector?
 
I spent several hours today in bright sunlight attempting to crimp those teeny tiny micro molex pins onto the teeny tiny 26 gage wires to mount in a molex connector for the elevator trim servo. I eventually was successful but not without a lot of swearing and multiple attempts. I have the BCT-1 crimping tool so that's not the issue, and eventually I got better with each pin in making the proper crimps without mangling the pin. No, the real problem was inserting the pins into the molex connector. Is there a special tool for this? It was almost impossible, and yes I did have them aligned properly for the key in each hole. God help me if I ever need to remove a pin for trouble shooting. How does one do that without destroying the pin/wire/connector?

If you're using the ones I'm thinking of (look like old school R/C servo connectors) I just used a magnifying headset, crimper, fine needle nose pliers, and careful finger pressure. AndI think a small plastic pushing stick?

I found the process somewhat enjoyable, actually.
 
I used a small connector for the pitch trim servo on my RV-8A, and later on I wondered why I bothered with a connector at all. Think about it: if you ever need to replace the trim servo, you're gonna have to install a new connector on the new servo which will come with bare leads. It's just as easy to use good quality crimped butt splices (e.g. AMP PIDG) to connect the servo leads to the wire harness. Leave an extra inch of slack in the harness, so in the unlikely event you ever need to replace the servo you can just snip out the old splices and install new ones.

Another technique I've seen for a low profile installation is to crimp D-sub pins & sockets on the servo and wire harness terminations, but instead of inserting them into D-sub connectors, simply plug them together with a piece of heat shrink over each pin/socket connection to insulate them and keep them from coming apart. This would not be a good idea if the wiring is ever likely to get yanked, but if it's properly supported/protected this is a clean way of connecting the servo to the harness without the bulk of a connector.

YMMV...
 
I spent several hours today in bright sunlight attempting to crimp those teeny tiny micro molex pins onto the teeny tiny 26 gage wires to mount in a molex connector for the elevator trim servo. I eventually was successful but not without a lot of swearing and multiple attempts. I have the BCT-1 crimping tool so that's not the issue, and eventually I got better with each pin in making the proper crimps without mangling the pin. No, the real problem was inserting the pins into the molex connector. Is there a special tool for this? It was almost impossible, and yes I did have them aligned properly for the key in each hole. God help me if I ever need to remove a pin for trouble shooting. How does one do that without destroying the pin/wire/connector?

After spending a day on a new RV-14 build tracking down an elevator trim servo wiring problem to one of these horrible connectors, I cut them out. These connectors are exceptionally fragile and the pin retaining clip breaks off. These connectors have no place in our RVs. Note - this connector was provided in the RV-14 kit.

I typically use a small molex for these servos. I use large pin molex plugs for anything with power, and D connectors for everything else.

Carl
 
Molex

Any connection up to 6 pins is .062" Molex. I have the tools (crimper and pin removal) and lots of practice from a previous life.
Over 6 pins is D-sub.
 
Different strokes for different folks....

If you search the forums you will find lots of posts from people who like the micro molex connectors a lot.
 
Aren't the mini used in the 12? Anyway, who thinks Molex can survive on making a single type of connector and terminal pins, they have dozens of different products.

OP: get the insert and extract tool. Oh - and a good headband magnifier. They are tricky little devils aren't they ;)
 
Are we referring to these?

50-57-9405_sml.jpg
70107-0004_sml.jpg


I'm using them for trim servos, especially my aileron trim (custom-built tab), because there's not enough room to get a D-sub where it needs to go.
 
Are we referring to these?

50-57-9405_sml.jpg
70107-0004_sml.jpg


I'm using them for trim servos, especially my aileron trim (custom-built tab), because there's not enough room to get a D-sub where it needs to go.

The Stein Air method uses dsub pins as connectors wire-to-wire, shrink wrapped so it takes even less space than a micro molex. So no need for an actual dsub connector, just the pins. The shrink wrap can be split to disconnect.
 
Different strokes for different folks....

If you search the forums you will find lots of posts from people who like the micro molex connectors a lot.


And many who need counselling after struggling with them.......

It is the Curse of the Wereengineer :D

They use them because they can :rolleyes:
 
Aeroelectric method

I suspect that the SteinAir method is actually the Aeroelectric (Bob Nuckolls) method. He just didn't post a youtube video. What Stein's video doesn't show is that you can 'stagger' the pins by clipping each mating pair longer/shorter than its neighbor(s). When you do that, you can keep the overall joint diameter almost as small as the wire itself, and it will 'key' each mating pair by length.

To answer maus92's question, current capacity is measured by capacity per pin; not the number of pins. The machined pins are rated at around 7 amps each. Most of us limit them to around 5A each, but you can use multiple pins for higher current. The technique is to use 20 awg 'ballast' wires ~12" long on each pin, and collect them into a splice with the main (heavier) conductor. The ballast wires provide a method to terminate into the small barrel of the pin, and help balance distribution of the current among the common pins.

Note that for something like trim motors, it's not amp ratings that is likely to bite you. There's almost no power carried there (it will run off a 9V transistor radio battery), and most of the wires just carry 'signal'. At those low levels, joint resistance is the big enemy, and molex style connectors are not gold plated. The Dsub pins are gold plated, and tend to be much more reliable in less than ideal environments.

All the above is covered in the Aeroelectric Connection book, and on the Matronics list.

edit: As mentioned, there's wide variation in opinion about this style pin. It's worth pointing out that the primary reason mfgrs moved from soldered joints to crimped joints was not joint reliability of a properly soldered joint, or stress risers in soldered joints (crimped terminals have them, too). The reason was two-fold: it's faster to train a line worker to squeeze a ratcheting crimper until it releases than to train him in how to make a reliable solder joint, and it's faster during production runs to crimp a joint using a pre-insulated terminal than it is to solder and then insulate/strain relief. The reason I mention this is that, as stated here, many have problems making up these miniature molex style connectors properly, but few have problems with Dsub pins, which they must master for the rest of their avionics anyway. Why not go the the known-reliable components *and* techniques?

Charlie
 
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At those low levels, joint resistance is the big enemy, and molex style connectors are not gold plated. The Dsub pins are gold plated, and tend to be much more reliable in less than ideal environments.

Whilst I am in agreement that gold connectors are a good thing in these low current applications, the connectors for the Molex plug specified at the top of the page are the SL seriese if I am not mistaken. I have found both tinned and gold plugs available for them, below is an example.
http://www.digikey.com.au/product-detail/en/molex-llc/0016020077/WM2563TR-ND/1656192
Tom.
 
D-sub solder pins

Another technique I've seen for a low profile installation is to crimp D-sub pins & sockets on the servo and wire harness terminations, but instead of inserting them into D-sub connectors, simply plug them together with a piece of heat shrink over each pin/socket connection to insulate them and keep them from coming apart. This would not be a good idea if the wiring is ever likely to get yanked, but if it's properly supported/protected this is a clean way of connecting the servo to the harness without the bulk of a connector.

YMMV...

I used this technique with staggered wire lengths. I found it easier to solder the skinny wires than crimp them. Reconnecting was necessary after painting.
 
I used this technique with staggered wire lengths. I found it easier to solder the skinny wires than crimp them. Reconnecting was necessary after painting.

That's where the good Daniels crimpers make a difference. I was never happy with a crimp on 26AWG wire into Dsub pins until I got the Daniels crimper.

Solder splices work really well for these types of connections as well.
 
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