My team is debating on which motor controller to use for next years competition. We currently have about 12 of the talon SR’s and are seriously considering an upgrade. If you have any recommendations or preference please let me know. Also, if anyone could please explain the pros and cons for each that would be very helpful.
It’s worth considering the srx for the can bus wiring. It can also be used with raw pwm, so it’s the best all around in my opinion. Great encoder integration too.
The spark is a great low cost way to keep your old robots running.
Otherwise, I haven’t found a real difference as far as performance. It basically comes down to cost and size. All the modern speed controllers are sealed, so metal chip resistance is not much of an issue anymore.
The SR is more efficient than the SRX (by a marginal amount), as was documented by CTR. If you’re OK with running PWM, there is absolutely no reason to switch to the SRX. That said, the SRX does have some advanced features that could be useful, if you aren’t handling PID and other controls in your models (though figuring out PID controls on a motor probably isn’t any more effective than just using LabVIEW to do it).
In summary, there isn’t anything to ‘upgrade’ to from where you are.
4901 has used all of them. If you want to get into CAN, then the Talon SRX is the ticket. If you’re on a budget, the Team Cockamamie Ri3D build ran (full disclosure: donated) Sparks just fine; we swiped them off the Team Cockamamie robot and dropped them into Sandstorm III eventually, and they ran just fine there too. We ran Talon SRs on Sandstorm II; for all of that robot’s faults, the electrical system wasn’t one of them.
In short, they’re all good. Which one is best depends on your team’s particular priorities of space on the robot, budget, and CAN utilization.
For PWM control, we were very happy with the Talon SR in 2014 and used them exclusively. We planned to use them in 2015 again, but then the new control system came out and we opted to upgrade to the TalonSRX. However, we still have quite a few of the Talon SR speed controllers in excellent condition, including a fair number of brand new ones, still in their original unopened boxes. If anybody out there reading this would like to purchase some of our remaining stock of Talon SR speed controllers, please send me a PM.
For CAN control, we have been extremely pleased with the Talon SRX in 2015 and 2016. They just work. No problems, no surprises. We have used the built-in PID control in both position-control and rate-control configurations with encoders wired directly to the Talon SRX. We would recommend the Talon SRX very highly for any teams looking to upgrade to PID control within the speed controllers.
I would suggest you pick up 4 SRX controllers and a couple of the encoder and analog break out boards and work with the SRX PID over the off season.
The control provided with running the pid on the controller, is just fantastic, but there is some learning curve, and it is good to get that behind you.
You don’t have use them for every motor, but when you want/need accurate control on positioning arms, or velocity on the shooter wheels, it is worth the extra dollars.
We have 4 of them on this years bot, 2 shooter wheels, shooter angle, and “wonder arm” angle. We actively switch between position mode and normal vbuss modes for coast down cool down events. We still use the Victor SR, for driveline, ball harvester, climber, climber deployment, as we like the form factor, and we actually have them mounted on top of each other, as the bot continually seemed to grow motors when mechanical team was making improvements.
Billfred has already mentioned what 4901 ran with.
5632 is running all Spark PWM motor controllers on our robot. I have been very pleased with their performance in all aspects and haven’t had to replace a single one yet over the course of 37 matches plus test time.
Im a big fan of the PWM retaining features that the housing of the controller has that helps keep the PWM cables secure even in a game like FIRST Stronghold. Additionally, our intake makes use of the limit switch features that are built into the device.
When it comes to CAN controlled devices. I would recommend the SRX for the benefits you get with their PID control abilities.
I’d just note that the srx is even more convenient if you’re okay with buying into the Vex ecosystem. The versaplanetary encoder and srx mag encoder are both pretty nice and plug straight into the talon srx. Possibly with an extension cable and connector unless you’re investing in the parts to make custom length cables.
254 absolutely loves the Talon SRX. Our entire robot is powered by them and we use the onboard PIDF controllers along with the CTRE encoder to control our turret angle, flywheel velocity, and drive wheel velocity for autonomous mode. Tuning these controllers was easier than anything we’ve tried in the past thanks to the heavy filtering and fast update rates they can achieve.
I recommend them to all teams and don’t see us switching away any time soon.
CAN enables you to do a lot more (we especially like the current draw measurement of the SRX’s), but with a daisy-chained architecture could also be a liability - if your CAN cable comes unplugged from the RIO, your whole robot is dead.
Our general philosophy of recent year(s) has been PWM-style controllers for drivetrain (where you need lots of raw super reliable power) and SRX/CAN controllers for things like shooter motors or arms which need finer control. Just a rule of thumb, though…
Updates after talking to our electrical lead:
I was mistaken, Spark controllers were not known to have an issue. SD540’s did have a low-voltage interesting behavior, but that was fixed in the B revision.
PWM controllers are also much lower cost. In reality, that’s what would drive us to use them unless there is a sensor associated with that particular mechanism.
We used the Talon SRX they have some nice upsides, just two things I didn’t like. The reset button is a little big and some of them got stuck on our bot. Also I wished they had a version for terminal studs, instead of everything being soldered in place.
Ideally you would use the Talon SRX where you need the PIDF controllers and then Sparks or TalonSR everywhere else.
If using the built in PID for drive control, are you guys using a gryo to keep the heading straight? If so, how do you keep it straight, as I don’t see a way to sync talons on different sides. Do you just adjust the velocity setpoint based on the gyro angle offset?
Quite simply, yes. There is a higher level controller on the robot adjusting for robot position (including heading). That controller generates wheel velocities which get fed into the Talon. This is nice because we can be generally confident the wheel will try as hard as possible to do the right thing without having to manage it manually.