Just wanted to put a warning out to all the teams using the new Neo motors from REV Robotics. The encoders required to run the motor (built in) have JST connectors that seem to break pretty easily and are of pretty short length. Make sure you have plenty of slack on your cables! We had a JST encoder connector break on us today with basically no tension on the wire while inserted. Seems to be a flaw in the design to have such small gauge wire built right into the motor and be non-user replaceable. Whereas with CIMcoders we can swap out the wire should it break, we’re basically out a Neo now.
I don’t know if this is an option for you but you can recrimp the connectors using the recommendations on REV’s site: Contact Housing Crimper
Also, when removing the encoder cable from the SPARK, do not pull directly on the wires. I’ve found using two screwdrivers to twist/wiggle the connector out works well.
Definitely an option we’re pursuing! Agreed on the screwdriver point as well. As of right now we’re a little confused as no one touched the robot (besides taking it on-off a cart) between working and broken wires. As of right now I’m looking into 3D-printing a tool to aid in removal. Will post if it comes out nice.
We used a lot of JST connectors like that at my last job. If the wire harnes manufacturer didn’t get the lengths of the wires just right, some of them will get extra tension and can break. The wires going to the outer positions need to be a bit longer. Rev may want to check with their manufacturer on this.
I wish the various manufacturers would stop using such small connectors. One with enough of a body protruding to get a good grip on isn’t that much taller and would make for a much more robust product.
I positively, absolutely, unabashedly HATE JST connectors. The encoders that we used for years from Andy Mark for their toughboxes had a JST connection. These encoders universally failed in 2 ways. Scratched disks from students and mentors who didn’t understand the assembly process, and having the wires leading into the JST connectors snapped off.
The connectors are great from the standpoint of a firm connection. They don’t need to be glued or otherwise retained and they never seem to come apart on their own. It is very difficult to take them apart in a limited space though. It’s equally difficult to train every one of your students to take them apart correctly every single time.
We struggle to teach some of our mentors to respect wiring. They grab things on the robot and move them without triple checking that they are fully detached, or move things without paying attention to whether the wiring has been retained and is away from gears etc. JST connectors that have tiny wires were usually a casualty waiting to happen.
Addendum: Swyft uses JST on their breakout boards. We took a look at them, and decided we’d actually prefer the JST on those rather than the PWM / lockless style on the Roborio that we have to affix in different manner. Then again, we can almost always access our Roborio, so many of my complaints about the JST connectors don’t apply to the Swyft boards.
Yes, for how they are mis-applied in FRC. Some connectors, like the ones used on the Neo motors are really meant for a one time connection such as when a large piece of equipment is first put together in the factory. They would only be unplugged by a trained technician, years later, when servicing the equipment. And that would only happen a few times in the life of the equipment. That is how they used them at my last place of employment so they were okay there.
The connectors meant for the one-time assembly are rated for as low as 10 mating cycles. I could not find any mating cycle rating for the JST connectors used on the NEO which usually indicates that it is low. In contrast, this micro USB connector is rated for 10000 mating cycles.
I haven’t quite seen a failure like that in my own testing. Multiple wires breaking at the same time takes considerable force. You can definitely repair the wires with the same contacts and housings listed in the SPARK MAX User’s Manual. An alternative would be to take half of one of our extension cables and splice it onto the NEO wires.
We have been using JST connectors in our FTC control system components for a couple years and have been quite happy with their robustness, retention force, and keyed features.
Others have recommended using a screwdriver to pry out the connector, which is perfectly OK. However, without a tool, I have found that pinching all 6 wires with my fingers close to the connector, I can apply even and gentle tension to remove the connectors without issue. Sometimes a gentle lateral motion of rocking back and forth, while still maintaining tension on all 6 wires, can help work the connector loose if it is particularly sticky.
By random chance, I had this exact connector sitting on my desk at work. It is literally the only connector that I have at my desk, and it happens to be this one. What are the odds?
Here are some other part numbers that will also work:
Some wire-to-board connectors, when properly crimped, are designed for removal via the wires: An excerpt from the JST Handling Guide for their various terminals, including the wire-to-board JST PH that is used on the NEO:
I want to double emphasize the need for proper slack and strain relief. With improper slack, you increase the chance of there being a failure. More from the JST Handling guide:
This may be correct if one strictly follows the guidelines from JST for just these connectors. Unfortunately, your recommendations will be taken out of context and applied to connectors for which pulling on the wires is NOT recommended.
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