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dmgauntt

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Posts: 27
Reply with quote  #1 
The Servos topic includes comments on problems with connectors; it seems appropriate to start a new topic on that issue.

There are a couple of problems that I have seen several times each with the PowerPole connectors over the years.

1) It is possible to assemble the connector incorrectly so that the black terminal and the red terminal are swapped.  Preventing this is an issue of QA for each hub, but they need to be aware that this is a possibility.

2) It is also possible to assemble the connector incorrectly so that you don't get a good metal-metal connection when the connectors are plugged together.  Correcting this involves pushing a jeweler's screwdriver into the connector to pull the terminal up over a plastic lip.  This is a much more subtle problem that is more likely to get through QA.

I wish that I could suggest a good substitute, but can't do so off the top of my head.

As for the Vex motor connectors, I routinely refer to those as "the worst connector ever designed".  The complete lack of strain relief on the connector is something unlike I have ever seen.  I suppose that this design may have an educational purpose in teaching the students about the importance of strain relief, but if so it goes over the top.
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jgraber

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Posts: 156
Reply with quote  #2 
There is nothing on the Rkit inventory list described as "Vex motor connectors".
Can you be more specific?    (use Rkit list descriptions below)
To which of the 2 ends do you refer to?

Here are some items from the Rkit inventory list:
Sensor wires with screw terminals 3wires
Sensor wires w screw terminals 2wire (white black)
Cortex Microcontroller mod with red/black plug
Motor Controller 7.2V 4A (MC#29)
Servo Power Adapters (resistor wires)
24" servo extension wire
40" servo extension wire (or 36" or 1m)
Motor cables with screw terminals 2wire (red black)
Large Motor
Small Motor
  

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dmgauntt

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Posts: 27
Reply with quote  #3 
Sorry about that; I usually try to be a bit more precise in my language.

This is a problem with the 2 wire end of the motor controller (mC#29) and the motor cables with screw terminals 2wire.  When they are connected, the connectors are joined only by the conductors; it is fairly easy to bend the joint and break the conductors.  It is uncommon to actually break the conductors, but bending them is fairly common.

I have taught my students to make strain relief by cutting ~2" lengths of the wooden dowel, lay it across the connected pieces, and then use cable ties to secure the wire on either side of the connector to the dowel.

The connectors for the servo extensions are not perfect, but a big improvement on this system because there is a plastic shroud on the female connector into which the plastic housing of the male connector fit; this protects the conductors from being bent if the joint is stressed.  Strain relief is still useful here to keep the cables from being pulled apart accidentally, but it is not needed to protect the parts from damage.

We have also had repeated problems with the cables that terminate at the Eurostyle screw terminal.  The wires can easily pull out of the metal aglet*, or perhaps break there.  When this happens, I simply have them strip about a 1/4" of insulation from the end of the wire, and then reinsert it into the screw terminal without the aglet.  It is not a difficult fix, so I really don't consider this a major problem.

------

* Aglet - a metal or plastic tube fixed tightly around each end of a shoelace.  I don't remember the correct term for the sheath at the end of a wire, so aglet will do.  For uses in literature, see "Taming of the Shrew" by Shakespeare (act III, scene I if I remember correctly), or "Phineas and Ferb", episode "Lights, Candace, Action!".

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Lancie1

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Reply with quote  #4 
 
* Aglet - a metal or plastic tube fixed tightly around each end of a shoelace.  I don't remember the correct term for the sheath at the end of a wire, so aglet will do.


The usual electrical term is ferrule.  Ferrules are used to terminate stranded wire for insertion into terminal blocks, and provide superior termination performance.
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RobbySmoot

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Reply with quote  #5 
Hi everyone...i am a new user here and by profession i am a hardware design engineer. First of all i would like to say thanks to @dmgauntt for sharing this information and adding new information to the previous thread. It is correct that the Aglet is nothing but a Ferrule, used to join the end of the wires tightly. Soon i will also share some more details about the connectors here.

complete pcb
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flareelectricals

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Reply with quote  #6 
Try using the tinned copper in line connector/ferrule to connect the wires.  I think this should do the job.
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maureenash

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Reply with quote  #7 
This is a problem with the 2 wire end of the motor controller and the motor cables with screw terminals 2wire. When they are connected, the connectors are joined only by the conductors.As in case of vex motor connectors, this design may have an educational purpose in teaching the students about the importance of strain relief. The custom essay writing service is to produce you easy and effective information for your essay that will help you to create your own work without fear.
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