blog; Motor Controller Options for 2015

[nuclearnerd]

I wonder if FRC would consider brushless motors & controllers in the future. Since the popularity of quadcopters exploded, there are tons of cheap options available

[Thad House]

If they run into a problem and these end up not being legal, I foresee a motor controller shortage next year. I'm glad we have about 20 talons, which should be enough for next year.

Also, not sure how I feel about the pigtails. Especially since they are only #12 gauge. I would have preferred to see #10 gauge, or a version with screw terminals for the teams that want to use them.

[AdamHeard]

Originally Posted by Thad House

If they run into a problem and these end up not being legal, I foresee a motor controller shortage next year. I'm glad we have about 20 talons, which should be enough for next year.

Also, not sure how I feel about the pigtails. Especially since they are only #12 gauge. I would have preferred to see #10 gauge, or a version with screw terminals for the teams that want to use them.

The screw terminals would have dictated a larger packaging.

We were planning on leaving anderson pigtails on each end of EVERY speed controller going forward on 973, glad they made that decision for us essentially.

It's different, but I don't see it being a problem. If we had pigtails for 10+ years then switched to screw terminals people would be bothered in the other direction.

[Jared]

Originally Posted by Thad House

Also, not sure how I feel about the pigtails. Especially since they are only #12 gauge. I would have preferred to see #10 gauge, or a version with screw terminals for the teams that want to use them.

I wouldn't be too worried. CIM motors come with even smaller #14 gauge wires, and teams have been fine with this. If you're very concerned with performance, you can trim the pigtails very short, and you'll end up with a very small voltage drop.

[Gdeaver]

We used andersons on the robot this year and were very happy with them. This change will be a good fit with our current wiring practice. Now the whole robot frame becomes the heat sink.

[Nate Laverdure]

Originally Posted by Gdeaver

Now the whole robot frame becomes the heat sink.

It's a cool thought, but the contact resistance probably still ensures that natural convection dominates.

[BBray_T1296]

Originally Posted by Gdeaver

We used andersons on the robot this year and were very happy with them. This change will be a good fit with our current wiring practice. Now the whole robot frame becomes the heat sink.

I realize these things probably aren't supposed to be grounded to their frame, but in the event that they are, I personally would still screw them through a non-conductive piece of material like corrugated plastic or lexan.

[Andrew Schreiber]

Originally Posted by BBray_T1296

I realize these things probably aren't supposed to be grounded to their frame, but in the event that they are, I personally would still screw them through a non-conductive piece of material like corrugated plastic or lexan.

The documents linked state that they are electrically isolated.

[BBray_T1296]

Originally Posted by Andrew Schreiber

The documents linked state that they are electrically isolated.

Fair enough.
Though I would still prefer using corrugated plastic. Not only because it is light, but you can punch mounting holes in it by simply shoving a screwdriver through it. To each his/her own of course.

[Andrew Schreiber]

Originally Posted by BBray_T1296

Fair enough.
Though I would still prefer using corrugated plastic. Not only because it is light, but you can punch mounting holes in it by simply shoving a screwdriver through it. To each his/her own of course.

VersaFrame holes can easily be used to mount these. Holes are already drilled.

[qnetjoe]

My only question is what is the pinout for feedback pins on the SRX?

I only counted 10 pins on the feedback connector, but the Jag has 12 ( 5 - encoder, 3 Analog Input, 2x2 Limit Switches). I am sure a few pins are doubled up but I wonder which ones?

[s1900ahon]

Originally Posted by qnetjoe

My only question is what is the pinout for feedback pins on the SRX?

I only counted 10 pins on the feedback connector, but the Jag has 12 ( 5 - encoder, 3 Analog Input, 2x2 Limit Switches). I am sure a few pins are doubled up but I wonder which ones?

Yeah, but of the 12 pins on the Jaguar, 4 of those were grounds. This was done to try to make each interface easy to wire. Using a unified connector accomplishes the same thing (and an interesting alternative).

Let's speculate.. that's fun. What I suspect is we'll find there is a certain amount of pin multiplexing (peripheral signals that share the same pins; the firmware connecting a single peripheral to a pin based on configured usage). Very common on MCUs.

Assuming that a connection can be established across either the CAN, USART, or SPI connection for control, that needs 6 of the 10 pins on the connector be distinct. Add 2 more for power and ground. That leaves 2 signals for a sensor.

End speculation.

However it ends up, it will be well thought out I'm sure.

[sanddrag]

Well, this will certainly change the way we do wiring a little bit, but I'm sure we'll still come up with a way to make it look nice. I like that the mounting holes are in a line parallel with the case and a nice round 2.000" apart, rather than at opposite corners across a diagonal. I also like that we can pack a bajillion of these into a small area, and do not need to design our chassis around the width of a row of speed controls.

Also, I like that I don't have to practically write a whole grant just to put some speed controls on our robot.

Thank you VEX and CTRE!

[RogerR]

Originally Posted by sanddrag

...Also, I like that I don't have to practically write a whole grant just to put some speed controls on our robot...

I've seen statements like this in several places, but it appears to me that they are essentially the same price as existing speed controller options. What am I missing that everyone else has noticed?

[cadandcookies]

Originally Posted by RogerR

I've seen statements like this in several places, but it appears to me that they are essentially the same price as existing speed controller options. What am I missing that everyone else has noticed?

I've been interpreting these statements as "It's really nice we won't have to buy ~$1000 of new speed controllers because our old ones are still legal." I don't have any background with a situation where teams had to replace all their speed controllers in one year, but then I've only been in FRC since 2011, so maybe someone who has been around longer can shed a historical light on this.