Electrical connectors on control system items

Hey All,
We have been working on a bunch of new products for upcoming seasons and wanted to get the community’s opinion on an internal debate we have been having at REV.

In the current control system there are numerous styles of electrical connectors, each one has it’s own advantages and disadvantages (cost, size, current carrying ability, easy of installation, robustness, etc) and there have been a few “standards” that have appeared over the years. While we are still in the phases of working on new projects I always think it is a good idea to question previous assumptions rather than just assume they are correct.

Here are all of the connectors that are commonly used

  • .1inch headers (PWM) - used for all signals to the roboRIO & motor controllers - minimal retention but cheap

  • Weidmuller wire-to-board - Used for CAN connections & module connections - expensive, good retention, requires precise wire striping

  • Wago - Used for the Power distribution board - Expensive, good for high current, very reliable

  • Screw terminals - Used on SPARK motor controllers & others - low cost, good retention, small, screws can strip/get lost

  • Spade terminals - Used on the Spike relay and wire to wire connections - cheap

  • Anderson Powerpole - main battery connector & commonly wire to wire connections - medium price, good quick release, hard to crimp without special tool

  • IDC connectors - used for MXP, SPI, & talon motor controllers

  • USB - Used on the roboRIO & other places

  • Barrel jack - used on the radio

  • RJ45 (ethernet) - Used on the radio & roboRIO

  • RJ11 - used on Jaguar motor controller

Here are some new connectors I would like opinions on.

JST connectors (PH series for example ) http://www.jst-mfg.com/product/detail_e.php?series=199 - As a replacement for PWM cables
XT Connectors (30 or 45) https://www.amazon.com/OOOUSE-XT60-Connector-Pairs-pairs/dp/B005FAPYXS instead of power poles or wagos
Deans connectors - https://www.amazon.com/dp/B00S7G4A14/ instead of power poles or wagos

So you tell us, What frustrates you or makes you happy about the existing connectors? What connectors do you hate and which ones do you like.

We are also open to other suggestions let your opinions fly.

The screw connector for powering the roboRIO (and previously cRIO). I don’t know if we were using it wrong, but especially on the cRIO, the wires would too frequently come out or be loose. I don’t think we’ve had an issue on the roboRIO, though.

I’m personally not a big fan of JST connectors for items that need to be plugged in/out with any frequency. I find the pins to be easily damaged if you try to seat a connector that’s not properly aligned. As a result they are nearly impossible to plug in to a sensor that’s buried in the robot. The Sharp IR sensors have this style connector on them, and we always terminate an adapter cable to 0.1" header pins in the event something needs to be swapped out between matches.

For a low conductor count cable (like PWM you mention) what would be the advantages of a JST connection? The only thing I can think of is that it’s keyed, can’t see there being appreciable space savings on a 3 pin cable.

For the XT and Deans connectors, I don’t have much experience with them myself, but i know they are the standard I’m the hobby RC market. I’m open to their use. Instructions on how to connect to them correctly, tools required, what gauge cable, sources for tested wire & tools, tips/tricks would probably be helpful for most teams as I’m not sure I’ve ever seen one on an FRC robot in the past 8 years. Maybe I’m not looking hard enough.

I’m a fan of male/female spade terminals. They’re cheap and reliable when crimped correctly. We usually mount little right angle male spade adapters on all motor controllers with screw terminals so that they can be swapped out quickly.

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I’m really not a fan of XT-series connectors, and solder-type connectors in general. It’s much harder to judge the quality of a solder joint than a crimped connection.

In my experience using these connectors with stranded wire causes solder to wick up into the wire a bit, causing the wire around the connection to become brittle and prone to have issues if not given adequate strain relief. Soldering in general is much more error-prone and time consuming than crimping a connection with the proper tool.

As the teacher on a team that prides itself on clean wiring, I like this thread and feel inclined to comment.

.1inch headers (PWM) - annoying and really time consuming to crimp and/or solder. All the cheap tools suck. I wouldn’t be opposed to something better (or maybe I just own the wrong tools).

Weidmuller wire-to-board - has been fine
Wago - Can be tough to access in tight spaces. Need to plan for tool access in the design and assembly processes. The big ones on the PDB are fine. Small ones can be annoying, but workable.
Screw terminals - Not opposed to these in the right application, but the problem with Victors in the past was finding a non-insulated flanged spade terminal for a #12 wire and s #6 screw that was narrow enough in width to properly fit the Victor. 
Spade terminals - Works well, fast crimping, can be tough to get off sometimes.
Anderson Powerpole - These work very well. Crimping is not an issue for us. I really wish there was a 4AWG SB50 terminal though. We also sometimes have issues with the PP30/45 and SB/50 series getting the terminal all the way in after crimping if the insulation is large or the crimp is slightly malformed. But once you get the terminals over the clip, it's flawless. It's a training issue more than anything.
IDC connectors - seem fine I guess
USB - Haven't used them in an FRC sense.
Barrel jack - Always concerned about losing contact. We put a lot of thought and effort into properly retaining this connector so it cannot come out.
RJ45 (ethernet) - We do not use off the shelf pre-made cables, to eliminate excessive length. We've had some issues properly crimping these. Also, the clips are fragile, and if there's a stiff boot on it, you risk breaking the port itself if the user does not have the finger strength to fully depress the boot before pulling the cable out. So for that reason, I'm weary.
RJ11 - Similar to what I mentioned above, but I haven't used RJ11s specifically.

Here are some new connectors I would like opinions on.

JST connectors (PH series for example ) - Seems plausible. I’d need to see and try the terminals and crimper.
XT connectors - Never. Short circuit risk on the solder cups and just the fact that you can’t crimp it.
Deans connectors - Never. The exposed terminals on an unplugged connection are a serious short circuit hazard for teams who don’t know what they’re doing and install that half of the connector to the wrong side of the circuit. PowerPoles do not have a male or female side.

For me I value the ability to combine connectors into one main block and the ability to easily differentiate between positive and negative connectors. The power-poles also come standard with quite a few different colours and accessories such as retention pins.

For the 2016 season, we built a turret mounted shooting mechanism. We had 5 motors on the shooting mechanism, with 3 CAN Talon SRX’s mounted onto the rotating component with all sensors going into the SRX’s via CAN. We utilised Anderson Powerpoles(45amp) because they enabled us to join the plugs into one central block, including the CAN via green and yellow powerpoles. We were able to unbolt our entire shooting mechanism and simply unplug the main plug in order to quickly switch out our turret mechanism with our spare.

I don’t believe this block mounting style is possible with the XT connectors or the Deans Connectors.

I’ve never had any experience with the jst connectors or the xt connectors but I would imagine the xt connectors to be pretty good. The deans connectors I have had experience with before. They are a bit of a pain to solder to but they are done correctly they hold well and when plugged together they are almost impossible to take apart. They also take up a small footprint compared to other connectors which is always a nice thing.

If you are wanting to use 4AWG or larger for battery cables, it is legal to utilise a SB120 connector,

I have a lot of experience with XT connectors as they are connector of choice for personal projects. I used to use Deans connectors but they are much easier to melt when soldering and occasionally the spring tabs would bend ruining the connector. XT connectors are also easier to solder than Deans because of the cups on the terminals.

Personally I would rather solder connectors than crimp as it requires less specialized equipment and lessens the chance of a intermittent or high resistance connection which can be very difficult to diagnose.

Another advantage of RC connectors is that they are gendered(male and female) unlike Anderson connectors. This prevents a user from plugging a battery into another battery or the motor side of a speed controller into a power source and destroying it.

I’ve never been a fan of JST connectors, they are very low amperage and only really useful for something like LEDs. They are also difficult to grip and pull apart without tugging on the wire.

I personally prefer powerpoles over both the Dean’s and XT connectors. You have to have a proper crimper for them, but once you do, they are pretty hard to mess up. Our electrical students use them wherever possible because they are quick, easy and they rarely have issues with them. Our students soldering ability tends to vary a lot, so soldered connections tend to require more TLC to ensure everything is solid.

I absolutely hate deans connectors. My kids all participate in RC (boats and cars). And these things are the #1 reason I see cars dead on the track. I’ve gotten packages of things where no matter how hot you get it or how careful you are they simply will not pass a pull test after you solder them. I’ve taken said packages to the hobby stores and they tried one and threw the rest away, and opened a new package.

I will stick with crimp style connectors. In marine applications, soldered connections are highly frowned upon by the certification organization because they are uncertain and are a brittle failure point in high vibration environments.

“.1inch headers (PWM) - used for all signals to the roboRIO & motor controllers - minimal retention but cheap”
I like the Hansen Hobbies latching connectors way more; the peace of mind and ease of use is great. Not too expensive either. That being said PWMs work fine for me too.

“Anderson Powerpole - main battery connector & commonly wire to wire connections - medium price, good quick release, hard to crimp without special tool”
I love how you can stack them into bunches, but they are very hard to put together and remove this way, especially if a single component in a bundle fails.

“RJ45 (ethernet) - Used on the radio & roboRIO”
I’ve thought about using these for non-ethernet applications due to the availability of crimpers, crimps, and cheap cable cost of many different lengths from digikey. I have used a few of these in non-FRC non-ethernet applications, and they’ve performed admirably.

I had not seen these before. They look like a great alternative to pwm cables. However I don’t see much of a need for them unless they were to become a standard connector on most FRC products. Great if you are joining 2 cables (such as at a joint or turret for quick removal). However if you dont have the latching socket on say the roborio, it just becomes a standard PWM with an extra piece of plastic.

I would love to see something like this become a standard.

I really like the connectors on the US Digital S4/E4 series encoders. Browsing around on their website, it looks like it’s a 1.25mm pitch Molex PicoBlade connector.

The big thing I enjoy about them are the friction locks, they feel much more secure than standard 0.1 header connectors. I wouldn’t mind a bigger pitch than 1.25mm though for FRC use though.

I HATE JST connectors. You can’t make them yourselves, they use 24 AWG wire (prone to breaking), and you have to tug on the wire to get them to disconnect (more damage potential). I’m trying to find an alternative to US Digital encoders solely because they use connectors with the same issues.

As to the others, I don’t like soldering when I can avoid it. I much prefer crimping as it is easier to assemble & maintain. I prefer the Anderson power poles over what are shown for a number of reasons. The individual parts aren’t polarized (but I can polarize them by how they are assembled). I don’t have to worry about keeping M & F components in stock. Can be assembled into larger blocks.

We use the Hansen hobbies crimper and it works well (~$40).

I like to call screw terminals like these the best bad connector you will use. They’re relativley versitile, flexible, easy-ish to use with medium pincounts. However they will never be better than a more specilised conector.

On to the OP’s question:
I’m not interested in any new connections unless there are some very good reasons. Inventory management is a PITA, and it’s much easier to maintain an inventory of 100x of one conector, vs 25x of 4 different ones. For this reason I’m willing to make reasonable comprimises on all the advantages/disadvantages you mentioned, for connectors already in common use.

This is all the more important if your intended market is ALL of FRC, ie not just the average to powerhouse teams that already have things like this worked out. Having helped many rookie and low-resource teams wire up robots, trust me when I say there is enough in the combination of Wago, Weildermuller, [3-pin only] PWM etc already.

It’s a little different if your targeting just the medium-powerhouse teams. As other others have already mentioned Powerpoles, custom .1in (ie other than 3pin PWM), rings and spades, IDC, USB and ethernet etc all have some really good use cases.

Huh, I’ve always hated those. The attached wires were always a pain and usually messy, plus unplugging them didn’t always go well.

We started using some custom .1in connectors this year for different sensors, like a 5-pin one for Grayhill encoders and some 2-pin ones. Those worked well when done correctly, but our quality control wasn’t great, and a few connectors made it onto the robot that might have given us some intermittent signals. We’re learning, though, and I think we’ll go back to them and use more next year.

We also had some trouble with several Weidmuller connectors. No matter how many times we tried with different wires that were the correct gauge and stripped the correct length, a few connectors just wouldn’t work. Others were perfect and lasted all season. We picked up some ferrules to try to address that next year.

The 3-pin connectors are decent. We wound up taping and zip-tying a lot together, though, so we might pick up some VEX EDR connector clips. I’m a bit disappointed that the RoboRIO has male pins. We had one of those connectors come loose despite us using 3D printed cable management/spacing inserts. Other than a giant 10-connector female-to-female converter that plugs into all of them and reinforces everything, I don’t really know how to address that.

I haven’t personally used the XT or Deans connectors, but, given the option, I would stick with Powerpoles. They can clip together to make large plugs, they’re easy to lock together, and we have tons of them stockpiled.

Deans Connectors: Hate these things. A’lot of RC’s use them, but I’ve always had issues with them.

Anderson Power Poles: Go with these. I absolutely love these. FTC switched over to a new control system that uses these in pretty much everything, so my teams have a large stockpile of them. After having the right tool, they are easy to work with! My teams love the fact that you can create large blocks of connections, which has already been said in this thread. Allows us to remove parts easily to work on parts of the robot or to switch out. Some of the electrical students on my FRC team saw them this past year, and want to make the switch to them next season.

Molex connectors (http://www.molex.com/webdocs/datasheets/pdf/en-us/0022013047_CRIMP_HOUSINGS.pdf). They are polarized and latch pretty well. We’ve gotten pretty good at crimping them.

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