blog; Motor Controller Options for 2015

[Tristan Lall]

Regarding the CAN bus, to some extent, there's always an aspect of star topology on the bus—but traditionally the stub length is short, possibly on the order of a couple of millimetres (in the case of a direct connection to an integrated CAN transceiver). Barring any strange internal arrangement on these controllers, if you leave one pair unconnected, you should still be able to make the connection downstream to the remaining pair, but your stub length will increase.

Here are some general suggestions for optimizing stub length, given other parameters.

[FrankJ]

Originally Posted by Tristan Lall

Regarding the CAN bus, to some extent, there's always an aspect of star topology on the bus—but traditionally the stub length is short, possibly on the order of a couple of millimetres (in the case of a direct connection to an integrated CAN transceiver). Barring any strange internal arrangement on these controllers, if you leave one pair unconnected, you should still be able to make the connection downstream to the remaining pair, but your stub length will increase.

Here are some general suggestions for optimizing stub length, given other parameters.

I think of a star topology as the line length being short (or 0) relative to the stub length. Very different than what the CAN spec recommends. Without doing the math, I think you can get away with something approaching a star topology in FRC because the entire bus length is short. I have also run just one terminating resistor without issues. But if I were to start having problems, one of the steps would be to make the bus wiring completely to spec.

Here is what the CIA-- the organization that maintains the CAN standard, not the American government entity with the same name has to say.

Network topology

This clause is most interesting for system designers.

Electrical signals on the bus are reflected at the ends of the electrical line unless measures against that have been taken. For the node to read the bus level correctly it is important that signal reflections are avoided. This is done by terminating the bus line with a termination resistor at both ends of the bus and by avoiding unnecessarily long stubs lines of the bus. The highest possible product of transmission rate and bus length line is achieved by keeping as close as possible to a single line structure and by terminating both ends of the line. Specific recommendations for this can be found in the according standards (i.e. ISO 11898-2 and -3).
...

[donkehote]

Originally Posted by Tristan Lall

As for Velcro, isn't it (usually) covered by exception G in R64? Its legality is not a very strong argument for thermal paste.

Best to let the Q&A sort it out, but by all means let FIRST know now that you anticipate it being an issue during the season.

Quoting the 2014 rules, NO exception for Velcro, any team who used it violated the modifying motor controllers rule. I wonder if we should check every robot, and overturn matches from this past season?

4.9.11 R64

The Driver Station software, cRIO, Power Distribution Board, Digital Sidecars, Analog Breakouts, Solenoid Breakouts,
RSL, 120A breaker, motor controllers, relay modules, Wireless Bridge, 12VDC-5VDC converter, and batteries shall not
be tampered with, modified, or adjusted in any way (tampering includes drilling, cutting, machining, gluing, rewiring,
disassembling, etc.), with the following exceptions:
Please note that the Driver Station application is a separate application from the
Dashboard. The Driver Station software may not be modified, while teams are expected
to customize their Dashboard code.
A. User programmable code in the cRIO may be customized.
B. DIP switches on the cRIO may be set (applies to cRIO-FRC only).
C. Motor controllers may be calibrated as described in owner's manuals.
D. Fans may be attached to motor controllers and may be powered from the power input terminals.
E. If powering the compressor, the fuse on a Spike H-Bridge Relay may be replaced with a 20A Snap-Action
circuit breaker.
F. Wires, cables, and signal lines may be connected via the standard connection points provided on the devices.
G. Fasteners may be used to attach the device to the OPERATOR CONSOLE or ROBOT.
H. Labeling may be applied to indicate device purpose, connectivity, functional performance, etc.
I. Brake/Coast jumpers on motor controllers may be changed from their default location.
J. Limit switch jumpers may be removed from a Jaguar motor controller and a custom limit switch circuit may be
page 63 / 93
substituted.
K. If CAN-bus functionality is used, the Jaguar firmware must be updated as required by FIRST (see Rule R67-D).
L. Devices may be repaired, provided the performance and specifications of the device after the repair are
identical to those before the repair.


Again, im saying that it should be left to the Q&A, and that lawyering rules to this point isnt what FIRST is about, and as I said in my first post in this thread

Originally Posted by donkehote

Your post reminds me of the bumper pool noodle tape issue from last year.

Some things don't need regulating IMHO.

The tape that many many teams had used for years to fabricate clean tidy bumpers was technically illegal, almost impossible to detect, and spawned a long thread on chief, only to be explicitly allowed by first. Why people keep dragging up the ridiculous argument against thermal paste (replace thermal paste with tape and your back in last years thread) is beyond me, just let the Q&A make the final call.

Come on guys, use some common sense, If adding fans is legal for the purposes of cooling, do you really think first wouldn't allow thermal paste for the same reason?

[Alan Anderson]

Originally Posted by donkehote

Quoting the 2014 rules, NO exception for Velcro...

4.9.11 R64
[...]
G. Fasteners may be used to attach the device to the OPERATOR CONSOLE or ROBOT.

Velcro is a brand of hook-and-loop fastener.

[FrankJ]

Originally Posted by donkehote

snip

Again, im saying that it should be left to the Q&A, and that lawyering rules to this point isnt what FIRST is about, and as I said in my first post in this thread



The tape that many many teams had used for years to fabricate clean tidy bumpers was technically illegal, almost impossible to detect, and spawned a long thread on chief, only to be explicitly allowed by first. Why people keep dragging up the ridiculous argument against thermal paste (replace thermal paste with tape and your back in last years thread) is beyond me, just let the Q&A make the final call.
...

Properly applied, the thermal paste will not be visible to the inspector so it shouldn't come up for discussion. If it does come up & in the inspector's judgement against the rules, it is easily removed. Unlike the thermal paste that is likely on the inside of the motor controller. Please note: I am not suggesting that anybody cheat. Hiding something from the inspector does not make it legal.

Remember it was response to a Q&A question that got bumper tape banned in the First place. After considered discussion, they wisely amended their position. Silliness abounds on all sides.

[donkehote]

Originally Posted by Alan Anderson

Velcro is a brand of hook-and-loop fastener.

Not to be stupid, but isnt it an adhesive or glue that attaches each side of the hook and loop to the speed controller? Essentially the same as gluing a nut onto the bottom of a speed controller. It IS a fastener, but its not attached with a fastener, its attached with an adhesive.

I do understand your point though.

[mklinker]

I would love to hear what procedures IRI and CTRE have in place for assessing demand and reacting quickly to the supply of the new motor controllers. Using the initial Talon release and the shortages that ensued along with IFI's struggles to match inventory with demand, motor controllers could be scarce this season. Vex shows no stock of the old Jaguar and Victor controllers to supplement. AndyMark appears to have some Talons.

I expect demand to be high for both of the newly designed controllers!

What will the restocking time frame look like? Is anyone else concerned?

I am looking forward to the new controllers!!!!!!!

[AdamHeard]

Originally Posted by mklinker

I would love to hear what procedures IRI and CTRE have in place for assessing demand and reacting quickly to the supply of the new motor controllers. Using the initial Talon release and the shortages that ensued along with IFI's struggles to match inventory with demand, motor controllers could be scarce this season. Vex shows no stock of the old Jaguar and Victor controllers to supplement. AndyMark appears to have some Talons.

I expect demand to be high for both of the newly designed controllers!

What will the restocking time frame look like? Is anyone else concerned?

I am looking forward to the new controllers!!!!!!!

I'm not concerned for a few reasons.

I imagine all parties involved have learned well from the previous events.

Another reason is essentially they are the only speed controller on the market for FRC. Predicted demand should be easier. It's not them predicting how many teams will reuse speed controllers, how many will buy the competitors, and how many will buy theirs. It's just them predicting how many teams will buy versus reuse.

When you compare this to the mechanical items it's not even fair. The purchase of mechanical components aren't an A or B or C thing, they're A1.... Z1242123. Even though Hex bearings are popular in FRC, I doubt anyone on chief would be able to accurately predict the amount purchased even IF they had access to all of the sales numbers from all of the venders (other than a lucky guess).

I don't think they owe a public explanation to us on HOW they plan to do it (such information is propriety and the kind of knowledge that is worth good money).

I'm pretty confidant it will be handled well.

Edit. Since the parties involved represent the combined only source for speed controllers for the last few years, they now have exact numbers for how many teams purchase versus reuse. Plus margin for teams upgrading.

[Jon Stratis]

I agree with Adam - I think they'll probably do alright with speed controllers. All the same, I personally would encourage veteran teams to hold off on purchasing new ones a little bit so that rookies can get what they need - Veterans simply have more options than rookies do, as we are fortunate enough to have controllers we can pull off old robots.

It's really something when you think about what sort of inventory they might have for this upcoming season. If we just estimate about 5 new speed controllers for every team (some teams won't get any, some teams will buy 20), then that's ~15,000 new speed controllers. With an average price of $70 (assuming even distribution between Talon and Victor), that's over $1,000,000 worth of speed controller stock for just one season!

Obviously, some major assumptions there. How many veteran teams will decide to use the "tried and true" speed controllers and avoid the new ones for at least 1 season? How many teams will decide to use all new ones? What will the mix be between PWM and CAN use with speed controllers and the new control system?

[mwtidd]

I find it a bit curious that they chose to utilize a single button to calibrate the speed controller, as well as switch between brake and coast modes.

[AdamHeard]

For reference. We plan to order 40 or so.

That's a good deal of our budget but we're at the point where we need more anyway and it's a good time to switch.

[Tom Line]

Originally Posted by AdamHeard

Another reason is essentially they are the only speed controller on the market for FRC.

That's the very unfortunate aspect of what is going on with the new speed controls. In the short 2 year time that the Talon came on the market, we saw an upgraded 888 and a price cut of around 50%.

I hope some creative FIRSTer can get involved and bring another competitive product to market. A single-source supplier for such a critical component usually isn't a good thing from a consumer's point of view. Alternatives are important.

[Andrew Schreiber]

Originally Posted by Tom Line

That's the very unfortunate aspect of what is going on with the new speed controls. In the short 2 year time that the Talon came on the market, we saw an upgraded 888 and a price cut of around 50%.

I hope some creative FIRSTer can get involved and bring another competitive product to market. A single-source supplier for such a critical component usually isn't a good thing from a consumer's point of view. Alternatives are important.

While I agree with you as a general rule I'm not sure much can be done here. In FRC these are the only games in town but even if you look at other brands that aren't FRC legal they are fairly close in price once you're comparing feature sets. (12V, 40A continuous, R/C control, Reversible) and I'd gladly pay the SMALL premium to get a brand that has a reputation for solid ESCs.

[Jon Stratis]

Originally Posted by Tom Line

That's the very unfortunate aspect of what is going on with the new speed controls. In the short 2 year time that the Talon came on the market, we saw an upgraded 888 and a price cut of around 50%.

I hope some creative FIRSTer can get involved and bring another competitive product to market. A single-source supplier for such a critical component usually isn't a good thing from a consumer's point of view. Alternatives are important.

Tom, isn't the entire control system single source? There's only one source for a RoboRio. There's only one company that makes the required PCM and PDP. We can only use one specific brand/model of router.

The competition comes in, I think, when FIRST put out the RFP for the new control system - companies had a chance to come in, show off what they had for everything (including speed controllers, if I remember correctly) and get themselves chosen to supply things for the next few years.

[Tom Line]

Originally Posted by Jon Stratis

Tom, isn't the entire control system single source? There's only one source for a RoboRio. There's only one company that makes the required PCM and PDP. We can only use one specific brand/model of router.

The competition comes in, I think, when FIRST put out the RFP for the new control system - companies had a chance to come in, show off what they had for everything (including speed controllers, if I remember correctly) and get themselves chosen to supply things for the next few years.

Yep - the control system is singled sourced. That makes perfect sense from a complexity and safety standpoint - those components work together in a number of ways.

A PWM driven speed controller is stand-alone enough that competition can still be created though. The rest of the control system, not so much, except possibly the VRM.