[DFTF] Motor & wires...

This is part of a series of posts called Drinking From The Firehose on getting Dr Joe back up to speed on All Things FIRST.

Today’s topic: Connecting wires to motors such as the BB, FP or AM motors in the kit.

My bias is to solder the leads, loop the motor wires back toward the can of the motor, then tie wrap the wires around the motor can as a strain relieve (and I would probably put in on a set of Anderson Powerpole connectors, but more on that in another thread).

But others have suggested using female spade connectors - crimping the connector to the wire and then just pushing the connector on the motor terminal.

What is the collective wisdom of the folks on CD as to the way to connect to them?

Pros, Cons, Pro Tips, pictures, anecdotes… …give 'em to me.

Joe J.

Depends…did you design the mechanism so it’s quite unlikely that you’ll need to replace the motor, or have to remove it? If so, then just solder and secure. But if you need to remove the motor or change it for whatever reason, and you are good at soldering things without accidentally melting the plastic motor parts, I’d suggest adding the Andersen connectors and soldering the wires to the motor. If you have trouble soldering things like that, then terminals to plug onto the motor would work. Either way, stress relief is important

We did exactly what you described: soldering to the leads, adding heatshrink, zip-tieing to the motor, and crimping on some Anderson Powerpoles. No problems with the setup at the San Diego regional.

For us, the BB motor terminals seem a little fragile and have broken off a few times. So now, our process is to crimp a spade terminal on a wire, solder the terminal to the motor (carefully) and then hot-glue the heck out of it to prevent minor contact/vibrating breaking the connection. After we started doing this we have had 0 problems with the motor connections, although we have seen at times that the hot-glue will melt slightly due to the motor heating up so we re-hotglue it and we’re good to go.

We have always gone with route one, soldering to the motor tabs we haven’t had to many issues with this as long as you have the zip ties.

Now I’m thinking about adding the hot glue idea as a little more support.

The big issue we’ve had is with novice soldering students being mistaken as veteran soldering students by a mentor asking “can you wire this motor up with andersons for me?” by mentors like me. When unsupervised (or supervised by a non-electronics mentor) they tend to use too much solder, bend the terminals, or both. This leads to solder or wire that almost touches the casing of the motor, and in some cases the solder does touch the casing when the wires are bent in certain ways.

If we didn’t have mentors on this team who knew electronics and how unforgiving they are, we would use crimped terminal connectors with some hot glue.

We crimp and solder female spade connectors to the wire, then solder the spade onto the motor terminal. It is much easier to solder the connector to the terminal than the bare wire and is much more robust.

We crimp and solder female connectors to our wires. We squeeze them closed (ever so slightly) to make sure it’s a nice tight fit. Then we put a couple drops of hot glue on to lock it in place.

Then we fold the wires back against the motor and zip tie them as strain relief. As a final measure, we cut a 1" long piece of PVC pipe, then cut a slot in the side. This slides onto the motor very nicely - 1.5" for 775 and 1" I believe for 550’s. It looks nice if you paint the PVC, and protects the end connectors from the almost inevitable contact they’ll receive with people around the robot. Make sure you don’t cover your fan vents with the PVC, and you’ll be good.

I’ve always done what you’ve described: solder, zip-tie to motor can, add connectors. Never had an issue.

I wouldn’t put just any old connector on the motor, I would use the connectors designed to go on the motor to ensure a good fit. My experience has been that these connectors are made for very small gauge wire (14-18awg) and thus soldering on 10-12awg is easier to ‘do it right.’

Joe,
We use a flag terminal of the correct size for this terminal. We solder the wire to the flag terminal and then push the terminal on the motor terminal. Then simply solder the flag terminal to the motor terminal, slip on a bit of heatshrink tubing and route the wires as you describe. This method gives you a low profile connection at the end of the motor and a secure termination of the motor.

Here’s one kind of flag terminal. The right size for your motor terminal leaves no wiggle room under the two folded over clip springs. Someone mentioned flattening them for a tighter fit. This may or may not help the connection. Al’s soldering suggestion will obviate the need for grip adjustment.

19008isoflag.jpg


19008isoflag.jpg

We use terminals and solder as well.

Guess: The cut PVC slides part way onto the terminals’ end of the motor, leaving part of it in contact with the case and the rest forming a cylindrical barrier to accidental contact with the terminals. The slot allows the PVC ring to get past the soldered wires and then expand slightly for a friction fit with the motor’s case.

If my guess is correct, is 1" of pipe enough for this?

This.

Traditionally, we just solder leads to the motors and put some kind of connector on it(in previous years and on practice bots: spade. On the competition bot: Anderson Power Poles). After reading this thread, I’ll look into flag connectors. Can anyone recommend a good flag connector supplier for BaneBots motors and crimper for them?

Whatever you choose to secure the leads to the motors, please make sure you aren’t covering the vents with wires, zip ties, PVC guards, etc.

Yep. We fold our wires over fairly hard so they don’t stick out more than about 3/4" from the motor (or so).