REV PH Wago Terminal Issues

Hi All,

We’ve been running into some wiring issues using the REV PH. As a good practice, we have been using ferrules for any application where bare wire is needed (PDP connections, PCM solenoid connections, most things that use a wago connection). It appears that even with our smallest ferrule, we cannot get them to fit into the slots on the new PH. We have resorted to tinning the wires so that we avoid single strands/messiness. It appears that at some point during our initial wiring job, the body of the wago connections has cracked.

Even using tinned wire seems to cause issues, as the slot width is very small. 3 of our wago connections, 1 solenoid, 1 power and 1 digital sensor also appear to be damaged.

Have any other teams run into issues using ferrules or other wiring issues with the PH?

-Will

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We have experienced this problems on the PDH in the small fused output, one of our connectors on the end cracked. We have also found that basically no ferrules fit into the pneumatic hub. Today we ordered many small ferrules less than 22 awg to try.

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The specs for the REV PH only list wire gauge (stranded/solid) from 24-20 AWG for the digital and solenoid channels, and unlike the other ports, do not give ferrules as an option. I would not recommend the use of ferrules for these very tiny ports, although potentially very small 24-22 AWG ferrules might work.

Thanks, noted. We found a tiny ferrule that actually fit, but they don’t hold.

I thought all these WAGO terminals are designed specifically not to use ferrules. Am I wrong?

I distinctly remember asking a REV representative about the use of Ferrules. They said they would be a good solution and can be used. Are we now seeing they were incorrect?

You should ask Rev what the manufacturer and part number is for those terminals and then look up the datasheet for the part to see what it says. If necessary, you may have to check with the Applications Engineers at the manufacturer for the connector.

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They are WAGO 250 series. As with other WAGO cage-clamp series connectors (including the PDP/PDH ones), WAGO recommends using bare wire instead of ferrules.

Under normal operating conditions, direct clamping (i.e., directly connecting a conductor to the terminal block’s current bar) provides optimal contact quality, because all risk factors arising from anti-splaying methods are prevented. Occasionally, conductor anti-splaying protection may be required, including various methods (see illustrations below).

Special requirements apply only in special application areas exposed to extremely corrosive atmospheres. In this case, we recommend using either solid copper conductors or fine-stranded copper conductors with properly crimped, tin-coated copper ferrules or copper pin terminals.

Anti-splaying methods require a terminal block one size larger than the nominal cross section of the conductor to be terminated. Ferruled conductor cross sections specified for individual products are based on WAGO’s Variocrimp square crimping technology. Gas-tight, crimped twin ferrules may be used, provided the ferrule is inserted all the way into the clamping unit and that there is a sufficient clearance and creepage distance between adjacent potentials.

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It would seem that due to the way wago connectors are assembled they can be split if you put enough lateral force on them. This could be caused by inserting too large a ferrule or the wire getting pulled from the side. I suspect that if you do put a ferrule or pin inside the connector and the wires gett pulled from the side it would make it easier to split the wago connector. Due to the lever-action from the rigid pin.

You should be able to get them together again but finding the puch button part might be hard.

Rev documentation recommends non-insulated ferrules if you would like to use ferrules.

Hope this is helpful.

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REV has since updated the documentation (Wiring the Pneumatic Hub - Pneumatic Hub) and removed all references to using ferrules.

[Edited: found the download linked in the original post. It is at the product page (https://www.wago.com/us/pcb-interconnect/1-conductor-pcb-terminal-strip/p/250-204#downloads), on the Downloads tab, after expanding the Documentation section.]

The initial WAGO 250-202 product summary highlights use of “push-in terminations for solid and ferruled conductors.” The Related Products tab lists several uninsulated and insulated ferrules available from WAGO that can be used with this terminal block.

I would propose that the repeated connections and disconnections as well as the uncontrolled workspace used by FRC Teams, including working in the pits during an event, create a condition where anti-splaying protection could be warranted. Most teams don’t have a skill certification process for working with these connections, so inexperienced technicians could also be reason to implement anti-splaying protections.

It would probably be good to get a free sample of the WAGO 250 Series terminal blocks to do some testing with the uninsulated and insulated ferrules listed in the Related Products tab. This way we don’t risk damage (or further damage) to the expensive control system components to find a suitable anti-splaying protection measures.

I agree. It could also result from a stiff plastic insulator that is too large being pressed hard into the connector to ensure the pin is in contact with the terminal bus.

This also brings up the need for implementing strain relief and immobilizing wires. Team Members who did not participate in FTC are probably unfamiliar with these design practices outlined in the FTC Wiring Guide (https://www.firstinspires.org/sites/default/files/uploads/resource_library/ftc/robot-wiring-guide.pdf). I would like to see similar recommendations added to the FRC Wiring Guide as they still apply and may be more important given the more demanding shock and vibration environments of FRC.

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Yes! I recall one Regional I did inspection at where after all the teams passed and were well into the Qual matches, I was asked to go help troubleshoot electrical problems with 3 different teams, all within one hour. All 3 teams had intermittent shorts due to stray strands touching the adjacent wires where too much insulation had been removed. Those connections are only 3 mm center-to-center so it is really easy to get shorts like that.

At several previous employers where they had highly trained staff doing the wiring work, they used ferrules as a matter of course on all their closely spaced connectors. They did this to avoid issues during assembly and during subsequent servicing. It appears that a lot of the FRC world needs to learn about DFM and DFS; HQ for the fields, the teams and some of the suppliers.

Interesting. I went back to the WAGO 250-202 product page and saw that the recommended strip length is 8.5 to 9.5 mm. Using Strip Length to Pin Spacing is a compelling reason for implementing Anti-Splaying Protections. This is an objective measure and could be applied to a variety of different connectors.

In this case, with a properly stripped wire, a loose strand would be capable of bridging two connections. Bridging a single connection seems like a good enough reason to take extra caution with the connection.

it seems the challenge in front of us is to find an appropriate anti-splaying protection that doesn’t create sufficient lateral force to crack the housing, even if wires are installed with extra zeal or adrenaline between Matches.

The good news is that WAGO 250 series connectors are available from DigiKey. If you haven’t put your voucher to use, this could be one thing to add to your order.

The bad news is that they either require a large minimum order (https://www.digikey.com/en/products/detail/wago-corporation/250-202/15657045) or are expensive (https://www.digikey.com/en/products/detail/wago-corporation/250-211-000-006/15582224).

Now WAGO does have a way to request a free sample (https://www.wago.com/us/250-series-request). I’ve tried a couple times and nothing has arrived. It doesn’t take much to fill out the request form, but a follow-up by phone would probably be helpful.

I submitted a sample request using my work email address. It is believable that the company I work for would use these parts. It is likely they screen the sample requests and only send them out when they think they may have a potential paying customer making the request.

Did you want to test the sample connector? It arrived at my P.O. box a few days ago.

I’m interested in getting several in hand to do mechanical characterizations of the connector. I’d like to try several different wire ferrules with different insulator configurations. The goal is to put together a curated parts list and some assembly instructions for teams to use in conjunction with this new connector.

I was talking with some other mentors just tonight who were saying that REV is still having delivery issues from several suppliers which are putting some of the control system components at risk. This makes we want to get back into this because teams don’t need to be putting their only available PH at risk of damage using the wrong wire ferrule or risk a wicker shorting the connection.

As REV’s supplier issues have persisted, I think this elevates the consequences of the risk and I’ll probably just purchase several of these from DigiKey to do characterizations and compatibility testing.

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It’s not just REV. I am working on the initial design stages for a new circuit board and have never spent as much time looking for what should be easy to get parts. Many of them are out of stock and won’t be in stock until some time in 2023 or even 2024.

I have the samples in an envelope. If you send me your mailing address in the DM, I will send them to you.