16 gauge solid core vs 14 gauge solid core (and Wago connectors)

[mhaeberli]

Hi!
The Wago power connectors for the roboRIO and the PCM, for example, are spec'd for 16 gauge solid core. We happen to have used 14 gauge solid core. Probably a bit of a "push" for the Wago connectors.
But - will this cause a problem for us at inspection?
Thanks,
Martin
FRC Team 3045 ("SWAT")

[mhaeberli]

A follow - up question - thoughts on the "inspection quality" vs "operational quality" - the latter being reliability on the field - of 16 AWG solid vs (tinned / untinned) 16 AWG stranded for the power connections from PDU to roboRIO and PCM...?

[GeeTwo]

I doubt that you would be ruled non-compliant for too large a wire by the inspectors. It's certainly not on the checklist.

That said, if you're having real difficulty shoving the wire into the WAGO, that's probably a practical issue somewhere down the road - either this year, when you don't get as much contact as you should, or down the road when the "springs" in the WAGOs have experienced an inelastic shift.

Further, from a practical standpoint, our team has moved each year towards having a greater percentage of stranded vs solid wire on our robot. While stranded does not make those nice, neat right angle turns that IBE members want to see, stranded is much more amenable to continued functioning if the two ends move relative to one another, as happens all too often in robotics. In utterly practical terms, if you buy wire locally, get it from NAPA or Auto Zone or O'Reilly's or Pep Boys, not Home Depot or Lowe's. (though we do buy a lot of frame stock and miscellaneous hardware from both HD and Lowes, including some critical sensor mountings!)

[MrRoboSteve]

We have always been 100% stranded wire. I don't recommend any solid wire on the robot.

Avoid placing wire in openings that are too large. Here's why: last year I fixed probably a half dozen robots at regionals with cRIO crashes, due to wires too large for the connector.

[wireties]

We have always been 100% stranded wire. I don't recommend any solid wire on the robot..


I second this - the wago-style connectors scare me if used with solid-core wire.

[dtengineering]

The only wiring rules I have seen involve colour and minimum gauge requirements.

There is a "catch all" category for anything that might create a safety hazard, but that is best reserved for situations where there actually is a safety hazard.

Jason

[GeeTwo]

We have always been 100% stranded wire. I don't recommend any solid wire on the robot.

No argument, though I do admit to a bit of solid (22-ga) wire this year. Unfortunately, it's on the most-moving wire we have - going to the lift plate. Fortunately, it's just powering our "FunLights", so we won't lose any points if it breaks on us, just a bit of cool factor. Our "touch" sensors on the lift plate have stranded wires.

[kstl99]

Solid wire is for houses, for a very good reason - metal fatigue. Since houses do not move or vibrate, solid is Vine. In machinery you almost never use solid as the vibrations will cause the wires to crack, the same as any metal that flexes. Robots vibrate more than most machines.

[nighterfighter]

In utterly practical terms, if you buy wire locally, get it from NAPA or Auto Zone or O'Reilly's or Pep Boys, not Home Depot or Lowe's. (though we do buy a lot of frame stock and miscellaneous hardware from both HD and Lowes, including some critical sensor mountings!)

Forgive my potential ignornace, but why not buy wire from Home Depot or Lowes? Is it just a pricing thing?

I guess we got lucky this year. We bought the plywood for the field elements and some wire from Home Depot this year, and got a discount because we were a local high school.

[vhcook]

Forgive my potential ignornace, but why not buy wire from Home Depot or Lowes? Is it just a pricing thing?

I guess we got lucky this year. We bought the plywood for the field elements and some wire from Home Depot this year, and got a discount because we were a local high school.

The wire you get at Home Depot, Lowes, and most hardware stores is very stiff and hard to bend. The automotive supply stores generally stock wire that bends more easily, which makes it substantially easier to work with.

[MrRoboSteve]

Wire has a couple attributes that make it better or worse for robot use:

type -- stranded vs solid
size -- gauge
insulation -- type

Auto supply houses stock wire that, in most cases, meets all three criteria. They aren't necessarily the cheapest places to buy wire, but they're accessible.

We sometimes use wire from Home Depot -- in particular we bought some stranded 12ga THHN this year, because we were there and needed it -- but the THHN insulation can be fairly stiff and difficult to work with. We probably should have gone and bought two rolls of 12ga wire at the auto parts store instead.

[MrForbes]

Wire from Home Depot or Lowe's is mostly intended for houses, which, as noted earlier, don't move. Robots move...like cars...so buying wire intended for cars is a better idea.

[wireties]

From the screensteplive stuff - "To maximize pullout force and minimize connection resistance wires should not be tinned (and ideally not twisted) before inserting into the Wago connector."

If they are recommending not tinning the wire (which would make it solid) or twisting the wire (so it would not flatten out when the jaws close) one would think solid core is also not recommended. Right?

[Al Skierkiewicz]

OK,
There is a few items here that can be answered.
1. Solid #14 for powering your devices will not violate any robot rules. That size of solid wire is more like a crowbar to the connectors though. What vibration the wire will receive will be transmitted into the connector. I am afraid early connector failure will be the result.
2. There are a variety of outlets for wire. We use MCM Electronics for a variety of wire, parts and tools. You can find them at http://www.mcmelectronics.com/
3. The Wago connectors do take solid wire but tinned, stranded wire is not the same. When you tin stranded wire, it does make the wire solid but in doing so, the outside strands cause a 'high spot' on the wire. These are what is contacting the the metal inside the connector and so all current must flow through these little spots on the outside of the wire. That increases the series resistance of the contact significantly. If you need to tin for making insertion easy, you can just add a little solder to the very end of the wire. The Wago connectors depend on this contact. If you really check into the specs, you will find that Wago downgrades the contact max current rating when used with solid wire simply due to the smaller contact area with solid wire. If you use the Wago ferrules, they are actually square in shape to maximize the contact area.

[Bruceb]

I was really hoping with the redesign of the control system we would get away from the troublesome wago connectors but instead we went to a smaller, more difficult to use size on things like the PCM and VRM. Why cant we just have screw terminals?

[Alan Anderson]

If you're having trouble using the Wago and Weidmuller connectors, it's probably because you're not using them properly. I find them simple, easy, and reliable. The only time I have any problems with them is when someone has bent, twisted, or otherwise mangled the wire after stripping it.

[MrForbes]

If we could make it so that the one student trained to connect wires well, is at all the meetings all night long, we would probably have fewer problems with them. But we end up having several students work on wiring, and usually it's a new thing to them. It just takes one wired installed not quite up to snuff, to knock out the robot.

Of course, we had the same problem when there were screw type connecters on the power distribution system back in 2008.

[MrRoboSteve]

Data point from one CSA:

Power connection issues I see a lot:

screw terminal loose -- speed controller, old PDB, circuit breaker
wire too big for Weidmuller terminal at RIO, comes out
bad crimping or incorrect use of solder connection
Anderson power connector not fully engaged

Power connection issues rarely seen:

wire loose at wago connector

[MrForbes]

Power connection issues rarely seen:

wire loose at wago connector

We've had at least two of them since we got our robot running. But it is easy to avoid...if you understand how the connectors work, and do the things recommended in this thread to make sure the wires are prepared and installed properly.

[wireties]

If you're having trouble using the Wago and Weidmuller connectors, it's probably because you're not using them properly. I find them simple, easy, and reliable. The only time I have any problems with them is when someone has bent, twisted, or otherwise mangled the wire after stripping it.

Preferring something else over the Wagos is a serious POV. We don't have too much trouble with Wago terminals but I'd feel better using screw terminals on the robots. My little company builds racks of equipment used on ships and planes for the Navy and Air Force. These are high vibration environments (like the robots) and Wago-like terminals are not allowed and for good reason. Tinning the wire, twisting the wire or using solid core wire is also not allowed but certain ferrules are allowed.

[cgmv123]

These are high vibration environments (like the robots) and Wago-like terminals are not allowed and for good reason.

Wouldn't constant force clamping terminals (like the Wagos and the Weidmullers) be better in high vibration environments than screws that can vibrate and come loose?

[GeeTwo]

Wouldn't constant force clamping terminals (like the Wagos and the Weidmullers) be better in high vibration environments than screws that can vibrate and come loose?

It's a matter of maintenance vs build-and-forget. If you're going to inspect and maintain the wiring every once in a while, the screws stay tight, but you can't really see if the W/W connectors are staying tight. If you build and then let things go, W&W are probably more likely to hold the wire because of the connector angle while the screw is more likely to come loose.

The tie breaker in my book is that if you use ring terminals, unless a screw rattles its way completely out of the threads to fall onto the deck, the wire isn't going anywhere.

And OBTW, the earlier responses on Home Depot and Lowe's were spot on.

[wireties]

Wouldn't constant force clamping terminals (like the Wagos and the Weidmullers) be better in high vibration environments than screws that can vibrate and come loose?

Good question - they are really kind of screw-clamp mechanisms so they are under tension and can't vibrate loose (within specs). Also the area of the connection from the terminal to the wire is larger, much larger.

[Al Skierkiewicz]

The WAGO style connectors do a pretty nice job in industrial environments but need additional wire management as part of the installation. Screw terminals don't require wire management but do benefit from this added step.
I installed control wiring inside our transmitter more than ten years ago. The transmitter was supplied with these compression type contacts. What I didn't like on those was the need to have a special tool made just for those terminals. We used #22 for most and up to #16 for the higher current requirements as specified by the manufacturer. All was stranded wire. I would guess that I wired somewhere in the neighborhood of 100 connectors over seven racks. Most of them had 10 to 20 contacts. The control cabinet has a panel that pretty much fills the rack. There has not been one failed connection. While the transmitter is firmly attached to the floor, we are on the 100th floor of Sears Tower. The building moves, a lot, and we are running cooling water through the final amplifier cabinet at 25 gallons per minute. There is not as much vibration as on ship but there is as much as an industrial installation in a factory.

[JDL]

Wago's are the way things are going in industry. Constant tension, vibration resistant, eliminates under or over torque and stripped or cross threaded screws.

Get your ferrule crimper ready and stock up on tiny flat heads.

[Al Skierkiewicz]

In rereading the thread, I should add this.
The WAGO terminals on the PDP are designed for stranded wire or WAGO ferrules. The manufacturer states that solid wire should be derated as the contact surface is reduced. The current handling ability of #14 solid is the same as #16 stranded due to the reduced surface within the contact. Tinned, stranded conductors should be derated even more. Depending on the person who performed the tinning operation, a #10 tinned stranded conductor could have the same current capability as a #16, un-tinned conductor. If you tinned your power wiring prior to inserting in the PDP and have a problem with motor performance, this is the first thing to replace.