ANOTHER glue thread!?!?!

[Sandy H.]

OK, not really a glue thread, but the electronics forum version. . . connectors.

I want some connectors vs hard wiring - some people will agree, some will disagree - I understand that. On older altimeters, I used Dean's and mini-Dean's, but these modern altimeters have about a billion connection options and I don't want to spend more money on connectors that the altimeter itself!

I have read that the JST-RCY seems to be decent if buying genuine product, but if getting it cheap, it is likely forged junk or at least poorly made. One person mentioned in a different post that they just started buying the pins and housings from Digikey and made their own with no failures after they switched. I like that idea.

I went to go find the part numbers and the rabbit hole was entered and I've spent the better parts of 4 hours playing the 'which connector' game for various reasons.

At the end of the day, I want a locking connector that I can crimp myself, using the proper type of tooling (I own about $2k in hand crimpers, so I understand that a crimp is only as good as the tooling, proper set-up and operator attention). I looked at TE, Molex and various others, but have just hit a roadblock as far as what to get that hopefully is compatible with tooling I already own, as I really don't want to buy any more crimpers. If there are approachable crimp dies that fit an existing crimp frame, I might be OK, but if I could use something I already own, that would be best.

I own ratcheting frames (1 MIL-spec and one generic, but both perform well) with generic dies and a few dedicated tools. One is a Molex that does 1433, 1444 and 1881 crimps, but I have no idea how to back out what housings use those crimps and are suitable to try (i.e. locking etc.).

If anybody has any suggestions or familiarity with the Molex product line, I would appreciate it. My Google-fu/Digikey-fu/Mouser-fu has failed me today.

Thanks for any help.

Sandy.

 

[OverTheTop]

My suggestion would be the Molex MicroFit 3.0 series. Reasonably priced, positive locking and of reasonable scale for HPR needs. Not so small as to be a pain to work with. Available in wire-wire and wire-board forms. Current capacity is very suitable for our needs. Reasonably low mass too.

https://www.molex.com/molex/products/family/microfit_30
If using them on a PCB I suggest using thruhole parts as they are more robust.

I have a generic crimper that does a great job on them, but I usually borrow the real crimper from work if I am not in a hurry.

We use them in our spectrometers and they are trouble-free and vibration-proof.

The only downside I know of is that they can become more difficult to separate when you have a high pin count.

 

[Sandy H.]

My suggestion would be the Molex MicroFit 3.0 series. Reasonably priced, positive locking and of reasonable scale for HPR needs. Not so small as to be a pain to work with. Available in wire-wire and wire-board forms. Current capacity is very suitable for our needs. Reasonably low mass too.

https://www.molex.com/molex/products/family/microfit_30
If using them on a PCB I suggest using thruhole parts as they are more robust.

I have a generic crimper that does a great job on them, but I usually borrow the real crimper from work if I am not in a hurry.

We use them in our spectrometers and they are trouble-free and vibration-proof.

The only downside I know of is that they can become more difficult to separate when you have a high pin count.

Awesome, that looks perfect. Regretfully, the terminals called out aren't listed as compatible with my Molex crimper, so it might mean yet another set of crimp pliers. Looks like they are fairly inexpensive, though. The $500 ones, get kind of annoying when you have to buy those. . .

Sandy.

 

[OverTheTop]

It sounds like you have a decent collection of crimpers so you should have something suitable. Have a look at IPC620 standard if you are not sure what target condition for crimps looks like when using non-specific crimper.

 

[Handeman]

What is the point of putting connectors in the av-bay?

What I use is a terminal on the av-bay ends and connect directly to the altimeter. The connections are soldered to the terminal strips in the av-bay caps and connected directly to the altimeter connections. The sled slides out of the av-bay on one end. Those wires are shorter. The ones that connect to the other end of the av-bay cap are long enough that I can pull the sled out of the av-bay. That allows a computer connection to download data.

No need for connectors. If I'm disassembling the av-bay that far I'll just disconnect all the connections directly from the altimeter.
If you are using a LiPo battery that needs to be charged all the time, I can understand it, but I've found that 9V batteries are usually good for about 3 years.

 

[OverTheTop]

What is the point of putting connectors in the av-bay?

No need for connectors. If I'm disassembling the av-bay that far I'll just disconnect all the connections directly from the altimeter.

I can easily remove the bulkhead and reconnect it without any chance of screwing up wire locations. One less chance for a mistake.

 

[Sandy H.]

What is the point of putting connectors in the av-bay?

What I use is a terminal on the av-bay ends and connect directly to the altimeter. The connections are soldered to the terminal strips in the av-bay caps and connected directly to the altimeter connections. The sled slides out of the av-bay on one end. Those wires are shorter. The ones that connect to the other end of the av-bay cap are long enough that I can pull the sled out of the av-bay. That allows a computer connection to download data.

No need for connectors. If I'm disassembling the av-bay that far I'll just disconnect all the connections directly from the altimeter.
If you are using a LiPo battery that needs to be charged all the time, I can understand it, but I've found that 9V batteries are usually good for about 3 years.

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The way you show above is how I've done a few and I've used Dean's connectors on a few.

The current iteration (not necessarily correct, just what I'm planning) is to solder the wires directly to the altimeter board, eliminating the screw terminals shown in your bottom picture. The ends of those soldered wires would go to connectors and the mating connectors would be soldered to the bulkheads as before. Basically switching a latching type connector for the screw terminals. I suspect that choosing the correct type of connector would allow this to be a more robust solution than the screw terminals, but I do not claim this as fact.

The side advantage would be that if I build all the altimeter bays with the same connector arrangement, it should be quicker to switch altimeters from rocket to rocket. I have designed all of my av-bays so far to use the same size sled, so going from 4" to 5.5" rockets (or between other 4" rockets) does not require removing the battery or altimeter from the sled. Regretfully, I imagine as I build more fiberglass rockets, this av-bay design might not be compatible with the bulkheads I have. That can probably be resolved.

Anyway, long-winded way for me to say why I'm trying it this time. Not sure if I'll like it or not. . .

Sandy.

 

[OverTheTop]

The current iteration (not necessarily correct, just what I'm planning) is to solder the wires directly to the altimeter board, eliminating the screw terminals shown in your bottom picture.

Just remember to support the wires as they come out of the PCB. Where the solder stops as it wicks up the strands creates a stress point where flexing the wires causes them to fail. Supporting them past this point greatly increases reliability. Hotmelt glue I have found is good for this purpose, and can be removed relatively easily if needed in the future. Supporting the wires further along takes the strain of that point also. Remember the wires weigh far more when under boost or recovery forces.

 

[Sandy H.]

Just remember to support the wires as they come out of the PCB. Where the solder stops as it wicks up the strands creates a stress point where flexing the wires causes them to fail. Supporting them past this point greatly increases reliability. Hotmelt glue I have found is good for this purpose, and can be removed relatively easily if needed in the future. Supporting the wires further along takes the strain of that point also. Remember the wires weigh far more when under boost or recovery forces.

My mental CAD was to wrap the wires around a 1/2"-ish drill blank to coil the end kind of like break lines are on a car about 1/4" from where I was going to solder the wires. I was thinking silicone to do the strain relief for the last 1/4", but hot glue makes more sense as it would be easier to get rid of if I had to do some re-work. I don't have a complete plan, but I assumed I would zip-tie the wires to the alt-bay board between the coil and the free end with a little slack.

This first version is going in a purpose built av-bay for a buddy, so it doesn't necessarily need to be as changeable as the version I want to switch between rockets.

Probably over thinking things, but that's how I roll. Very good point about the solder wicking, though. That should be addressed, as it is going to happen and rockets are a bit more dynamic than most electronic projects. . .

Sandy.

 

[OverTheTop]

Silicone RTV could work as well. Sounds like you are thinking about the right things.