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Best Type of Avionics Electrical Connectors?

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Yukon@K-9 Rocket Tech

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Hello everyone! I'm in the middle of designing a avionics boards for my rockets. My previous boards all used header pins and screw terminals, which are okay but not the most secure things in the world. I want something really secure like a D sub, but less bulky (Also this is really not practical for this scale, but they're cool lol). I don't like JST XH because they're not the most durable. Also what is the most common battery connector on most avionics boards? I see plenty of screw terminals for the battery input, but I'm curious about more secure alternatives. Any suggestions?
 

AllDigital

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I’ve found terminal screws to be the most reliable, as long as they are sized correctly and use the appropriate gauge (Stranded) wire. Also, backed up with zip ties for good cable management. I’ve tried 3-4 different JST connectors and still use them on my PCBs for some connected functions, but for power and switch I am only using screws (Also using a cap). I had a number of battery connection issues at > Mach 1 and/or >12 G’s, so I tried a bunch of different solutions. Terminal screws and a capacitor are working best for me.
 

Yukon@K-9 Rocket Tech

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I’ve found terminal screws to be the most reliable, as long as they are sized correctly and use the appropriate gauge (Stranded) wire. Also, backed up with zip ties for good cable management. I’ve tried 3-4 different JST connectors and still use them on my PCBs for some connected functions, but for power and switch I am only using screws (Also using a cap). I had a number of battery connection issues at > Mach 1 and/or >12 G’s, so I tried a bunch of different solutions. Terminal screws and a capacitor are working best for me.
Hmmm okay, thank you. Guess that's the way I should stick to for switch and battery terminal. I still want something different for different modules.
 

cerving

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I'm a bit prejudiced, of course, but I prefer to solder the wires directly to the PC boards, and on many (if not most...) of my rockets there are no terminal blocks or connectors at all. Just run the wires through the bulkplates, and seal them off with hot melt or modeling putty. Tin the ends, and just twist and tape the ematches directly to them. Fewer connections = fewer points of failure.
 

H. Craig Miller

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I prefer terminal blocks on the battery connections, with JST connectors for the outputs. Makes launch prep much easier.

AV-Bay.Sled.Raven-4.Rev.01.jpg


And, this setup allows you to swap out sleds (altimeters) in a matter of about 5 minutes or less.
 

Voyager1

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I tend to use screw terminals too. In fact, I have them installed on all of Cris' Protons and Quantums. :)
For in-line connections, where necessary, I will use the in-line Molex connectors. I dislike the JST connectors.
Generally, I will feed deployment wiring from the ejection pots/vials directly through the avbay bulkplates to the altimeters' screw terminals. I seal over the bulkplate holes with masking tape. It tends to get a bit busy around my avbay bulkplates because I typically employ redundant dual deployment. So, the fewer connections; the better.
 

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OverTheTop

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I tend to use a lot of JST connectors (XH, EH, PH series) and have had no problems. If I want something a little more robust I will use Molex, typically Microfit 3.0 series, connectors. They are positive locking which is an advantage over the typical JST connectors. If you need something more petite than the Microfit I think Molex now have Nanofit (and I seem to remember Picofit) which are similar but smaller pitch and volume.

As for pins I use tin-plated exclusively. Gold can give you wonderful connections if they are kept pristine clean. Some chemical residues can degrade them quickly. We found this at work with our spectrometers, so gold is not normally used in production equipment. The customer labs have all sorts of air quality issues that attack the gold.
 

Voyager1

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My main issue with the JST connectors is that I feel as if I'm about to pull the cable out of them when disconnecting them with my clumsy paws. Yes, they are reliable, but I do prefer the positive locking of the Molex connectors.
 

gtg738w

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If you want more secure, solder directly to the board and then put the connector in line. The XT-30 are reasonably small and are bullet power connectors. Most others you see are only rated for signal applications.
 

cwbullet

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If you want more secure, solder directly to the board and then put the connector in line. The XT-30 are reasonably small and are bullet power connectors. Most others you see are only rated for signal applications.
I use XT connectors on our launch system and my 3D printer. They are near bulletproof.
 

OverTheTop

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When using screw terminals, I prefer to put ferrules on the ends of the wires going into the terminals.
That's how it is supposed to be done :) . And another comment for others, definitely don't tin (solder) the ends you are putting into the screw terminals, unless you want to have to nip them up before each flight. The solder creeps under pressure and the connection can loosen.
 

Bruce

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Could you possibly post a picture of the ferrules that you use on the ends of the wires going into the terminals?
 

dvdsnyd

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I'm a bit prejudiced, of course, but I prefer to solder the wires directly to the PC boards, and on many (if not most...) of my rockets there are no terminal blocks or connectors at all. Just run the wires through the bulkplates, and seal them off with hot melt or modeling putty. Tin the ends, and just twist and tape the ematches directly to them. Fewer connections = fewer points of failure.
Cris,
With this setup, are your electronics pretty much dedicated to each rocket?
 

jderimig

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As other have mentioned never put tinned or stranded wire in a screw terminal and leave like that for extended periods. Use ferrules or single conductor wire.
 

cerving

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Cris,
With this setup, are your electronics pretty much dedicated to each rocket?
More or less... I generally don't swap out the electronics, except in a couple of rockets that are used as testbeds. Of course, I may be a special case... I have a lot of them laying around, since I test every version of every Eggtimer board, both prototypes and production. I have a few in rockets that never made it to production, for one reason or another... usually minor things like changing the spacing on the connectors.
 

Bruce

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Is it recommended to use ferrules for ignitor wires on a dual deploy or staged rocket?

Or would the non stranded wire would be OK without them?
 

TomR

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Hi Guys-
Electronics isn't really in my wheelhouse. I tried looking on Digi-Key and there are virtually thousands of choices. Does anyone have part numbers for the entire male/female/contact assemblies for either Molex or JST?
Mucho Gracias
 

stantonjtroy

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This is what I use, from Amazon.

View attachment 432594
2nd what Craig is using. In addition on each end of the AV Bay, I use opposite plug types (Male plug drogue, Female plug Main. Or vise versa) That helps prevent plugging it up backward while prepping with field distractions. I have these run out to screw terminals on the bulkhead by the ejection mortar. Makes hooking up the E-match easier.
 

Yukon@K-9 Rocket Tech

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I'm a bit prejudiced, of course, but I prefer to solder the wires directly to the PC boards, and on many (if not most...) of my rockets there are no terminal blocks or connectors at all. Just run the wires through the bulkplates, and seal them off with hot melt or modeling putty. Tin the ends, and just twist and tape the ematches directly to them. Fewer connections = fewer points of failure.
Hmmm good point, I may go that route for vital components
 

Yukon@K-9 Rocket Tech

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I tend to use a lot of JST connectors (XH, EH, PH series) and have had no problems. If I want something a little more robust I will use Molex, typically Microfit 3.0 series, connectors. They are positive locking which is an advantage over the typical JST connectors. If you need something more petite than the Microfit I think Molex now have Nanofit (and I seem to remember Picofit) which are similar but smaller pitch and volume.

As for pins I use tin-plated exclusively. Gold can give you wonderful connections if they are kept pristine clean. Some chemical residues can degrade them quickly. We found this at work with our spectrometers, so gold is not normally used in production equipment. The customer labs have all sorts of air quality issues that attack the gold.
That's interesting! I'll take note of that. I guess a lot of us have that assumption Gold=best connectors but that isn't always the case
 

Reinhard

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Hi Guys-
Electronics isn't really in my wheelhouse. I tried looking on Digi-Key and there are virtually thousands of choices. Does anyone have part numbers for the entire male/female/contact assemblies for either Molex or JST?
Mucho Gracias
Digikey is the right place if you want to buy the parts to put connectors on your own cable. However, if you're looking for pairs of male and female connectors with wires already attached, search for "JST SM" on places like Amazon or Ebay. Those are the black connectors, but you will also find a bunch of JST RCY (the red ones). I had a least one bad experience with JST RCY (they are non-locking and their keying against reverse polarity is not robust), so I avoid them. Prewired Molex connectors (especially the male ones) are much harder to come by.

Reinhard
 
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