0

What connectors should I standardize on?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

What connectors should I standardize on?

by JeffGilbert on Wed Jun 12, 2019 5:08 pm

I am building an I/O PCB Pi hat which will have 8 connectors to off board sensors. What type of tht connector headers should I standardize on. It seems like jst-sh, jst-xh and molex pico blade are common and would work just fine for me. Is one more commonly used and more widely compatible, durable, etc? None of my sensors have connectors, so no guidance there. Asking before sending my first prototype board design to JLCPCB for manufacturing. (Next I'll ask about Beta vs VHS ;-)
Having a great time getting back in to electronics/ r-Pi after a 30 year hiatus.
-Jeff

JeffGilbert
 
Posts: 2
Joined: Wed Jun 12, 2019 3:03 pm

Re: What connectors should I standardize on?

by adafruit_support_mike on Sat Jun 15, 2019 3:49 am

Industrially, there's a widespread and aggressively maintained lack of any coherent standard. It's one of the places where manufacturers can maintain lock-in on hardware.. it's usually easier to buy replacement parts from the manufacturer than to skim through datasheets for the bajillion vaguely similar connectors hoping to find a match.

In practical terms, use connectors that you like, and that make sense for your project.

Pin header is everywhere because it's comparatively cheap, easy, and makes sense. JST connectors are keyed, making them excellent for things like power connections, where Murphy's Law only has to win once to kill a board. Both tend to be used for semi-permanent connections, like a device assembled from modular components that only has to be put togther once, then later you need the option to pull one module and replace it with another. Making and breaking the connections over and over stops being fun quickly.

For connections that do need to be made and broken repeatedly, its more convenient to use things like banana plugs, RCA jacks, 4P4C/6P6C/8P8C (phone and Ethernet) modular connectors, or DIN connectors. They're made for easy plugging and unplugging, and the choice usually comes down to a tradeoff between size and the number of connections you need to make at once. DIN connectors are the most flexible in that respect, coming in variants from 3 to 8 connections, but tend to be kind of bulky.

There are also basic categories of connections: board-to-board (pin header), cable-to-board (banana, JST, RCA, modular, and DIN), and cable-to-cable (DIN). The qualities that make pin header great at board-to-board connections make it a nuisance for cable-to-cable connections, and the only reason to use RCA or DIN for board-to-board connections would be to submit it for design review on April Fools Day.

So with the different kinds of connection jobs, no single connector family is good at everything. Try to pick one go-to solution for each of the major options: b/b, b/c, c/c and few/many make-break cycles, then acquire a couple of fallback options in each category as you need them. Prefer keyed connectors over reversible ones unless you've specifically designed the signals to work in all possible orientations.

In most cases you can narrow a connection problem down to a small set of options, then choose the one that you like best for a specific application.

It's also worth noting that any board-to-cable connection problem can be turned into a cable-to-cable connection problem if you're willing to live with a squid: a board with a group of permanently-connected short cables with c/c connectors at the ends. I don't think there's any such thing as a tidy squid, but they make it *really* easy to break one connection, re-make it, or swap in a different one.

adafruit_support_mike
 
Posts: 57354
Joined: Thu Feb 11, 2010 2:51 pm

Re: What connectors should I standardize on?

by JeffGilbert on Sun Jun 16, 2019 11:27 am

Thanks Mike! That's a brilliant explanation, worthy of a FAQ
aggressively maintained lack of standard
- LOL

JeffGilbert
 
Posts: 2
Joined: Wed Jun 12, 2019 3:03 pm

Please be positive and constructive with your questions and comments.