Falcon / NEO pros/ cons

Hello
As I’ve been reading more and more about motors, I’ve become more and more confused. I’ve attempted to try to organize the pros and cons of both motors, and if you could help me fill out the rest, I’d appreciate it

NEO
Pro
Tried and Tested
Not significantly worse than Falcon based off of power
Cheaper
No integrated motor controller

Cons
Had some issues before
No integrated motor controller
Marginally worse power than Falcon
Worse encoder (How bad is it, I’d like to know)

Falcons:
Pros
Integrated motor controller
Marginally better performance
Built in/ better encoder
Integrated motor controller (fewer points of failure )
Output shaft

Cons
Integrated motor controller (Single point of failure )
Has never been tested by teams
Price is higher

9 Likes

I see what you mean but I feel like you not giving the Falcon 500 enough credit.
When you look at the motors based on power alone you’re nullifying nearly half of the Falcons possible output range. At max stall current, you’re looking at 180% more torque and 112% more output speed. This difference really illustrates the Falcons strength witch looks to be in my opinion 4 motor drive trains or other applications where 2 or more motors are used. The raw power of this motor will allow for things like elevators and shooters that commonly needed 2 motors, a gearbox, and an external encoder to be simplified and made commonly available to more FIRST teams.

I am total with you on the testing side of things, however, I have high hopes for the Falcon 500 especially because of the experience VEX and Cross the Road have but a new motor is a new motor.

TLDR;
POWER POWER POWER. The Falcon while not only making a near-perfect drop-in replacement for all CIM style motors also now gives us the ability to replace those pesky multi 775 gearboxes. 1 motor with the power of 2.

I cannot wait to see what teams do with this new technology. this motor is not an end all be all but I do see it replacing the 775 and NEO as the king of motors.

WAIT it costs $135?
never mind it sucks. (JK)

6 Likes

I want to replace our DiCIMate elevator Gearboxes with one of the Falcons to see how it works

1 Like

The biggest plus for the Falcons may be the CTRE libraries and the ease of integrating them into an existing base of knowledge. After a year, the Neo and Spark Max still seem to have “less” than CTRE on this point.

(I’m not a programmer, this opinion has been forwarded from our programming mentors and students, who I stand with since they are smarter than me)

17 Likes

For the average team, there is very little functional difference between the Spark MAX and the competing CTRE products. REV has (in my opinion) cleaner documentation than CTRE.

Let me remind the average team that the majority of your robots can be controlled with just a P loop. Seriously. Don’t overdo it. You do not need a perfectly motion profiled elevator in order to score things.

6 Likes

At max stall current, you’re looking at 180% more torque and 112% more output speed

But you will never be at max stall current, and if you are, it’s because your robot’s on fire and something has shorted.

When you’re actually looking at breaker-limited performance, the Falcon gives actually very little benefit over the Neo. It’s a 10-30W difference over the operating range, if I remember correctly. That’s going to be negligible if you’re actually comparing the motors based on real-world performance.

24 Likes

From what I’m getting at:
They are better, if we ever get a breaker that is more than 40A

I appreciate what you wrote though, and it’ll help guide our team in picking what we’ll get

4 Likes

It’s really really bad
Only 42 Clicks per rotation is insanely low, and you can’t plug in another encoder to the Spark Max while using it. This means that you can’t run your PID loops on the motor controller, which is less than optimal.
We couldn’t figure out how to run our motion profiles on NEO’s… The Falcon makes it possible

2 Likes

Can I take a second to question this? What level of accuracy do you need on an elevator or drivetrain where 42 ppr is not enough? Using 4" wheels with a 6.67 gear ratio gives an accuracy of roughly 0.05". On an elevator, using a 1" pulley with a 15:1 gear ratio yields an accuracy of 0.004" (I think).

Additionally, running a control loop on the RIO is… not that bad either. There is an excessively minimal difference in performance. Your vision loops using a limelight probably ran on the RIO - and pretty sure they ran just fine. Are you genuinely able to tell the difference in robot performance between a control loop updating at 20ms vs 1ms?

And for my last hot take of this post: one does not need motion profiling to do any of:

  1. Educate students on control systems
  2. Educate students on robotics
  3. Win a match
  4. Win a regional
  5. Win a world championship

P and PD loops on position are “good enough” for 99.9% of teams in FIRST. I’ve helped multiple teams reach IRI level autos using just a P loop for path following.

15 Likes

Per watt of input power, the output power of the NEO is within 3W of the Falcon. There is effectively no performance difference between the two motors. The extra power of the Falcon only shows up when you’re over the 120A limit of the main breaker (and well, well over the 40A of the PDB breaker).

8 Likes

It really doesn’t matter. The issue with both motors is that usually what you want to be measuring is a few stages down from the motors, so backlash is the real evil.

Our autos this year only used the NEO internal encoders for telemetry and we were quite happy with the accuracy and repeatability. I would heavily reccomend going through Justin’s math on your system and see if encoder counts is the real culprit.

If you take a look at the REV Trello page, they have adding external encoder support to their current sprint. I would suspect that this will be rolled out for the 2020 season.

13 Likes

The main issue is with velocity control, for our auton path following we needed a better encoder(but I really can’t say much more than that, I’m the mechanical lead)
What I do know is that our programmers having a really hard time with everything that need good velocity control

3 Likes

One of the things we may be implementing as a team to combat the issue of backlash with integrated encoders is to have simpler gearboxes (single stage) in our drive bases this year. Currently we are designing and building a machine to test this.

I’m pretty sure both motors run the exact same speed at stall…

33 Likes

You know, it takes more letters to type out Falcon than it does NEO. That’s a pretty big con. It’s clearly half as efficient.

40 Likes

However, you also don’t need to hit caps lock or shift as much, which requires extending your fingers more, so the effect on efficiency is more complicated than that.

8 Likes

If you’re going that far, I mean, Falcon has CON built in…

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A Falcon is a bird that soars high

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think how many of these motors 842 is gonna have to buy!

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FWIW, we ran velocity profiling on our elevator arm in 2019 with zero issues related to the motor/controller combo. Caveat: the gearbox reduction between motor and end effector is probably an order of magnitude slower than what you were working with.

If velocity measurement resolution is the limiting factor, it usually manifests as a noticeable quantization in your measured velocity (IE - you are commanding 100 RPM, but the control system acts erratically because it can only measure 70, 90 ,110, 130, etc. RPM).

Corroborating your statements - 254 did make mention the resolution was slightly too low for their purposes.