New Talon vs New Victor

[Qbot2640]

Originally Posted by Jon Stratis

...Besides, if you end up using pneumatics, you'll be using CAN for that! It really is rather simple, you just have to give it a go... and having Talons on hand will allow you do experiment with that.

We always use pneumatics for something, but we have always used 12 volt solenoids with Spike relays. Can we no longer do that?

Originally Posted by Jon Stratis

If you're building two robots, why not use old controllers for the second one? Take them off an old robot, and have at it - the size difference may mean you team has to get creative in mounting things for the second robot, but there isn't much reason to spend all that extra money just for the second robot - old Talon, Jags, or Victors will do the same job. Of course, if you want the extra controllers for backups at competition, that's a whole other issue..

We'd really like the two robots to be as identical as possible - at least the control system. What we might try to do is create a control system module that we can switch out between the two. Then buy a few spares to be backups (as you mention).

Originally Posted by Brian Selle

...You could also purchase 1 or 2 Talons to go along with the group of Victors. Since they work with PWM input it's a simple software update to switch between the two.

This is probably the best idea. Get a few for future development, and/or to satisfy us if we get more ambitious than we thought.

[Chadfrom308]

Honestly, I think our team is going to do some CAN this year (our first year doing it too). Not only is it GREAT experience to have, it also isn't too hard. I worked with a CAN shield for Arduino, and I can say that it was much simpler than I expected it to be. It is also less cluttery than running PWM to everywhere. Plus, offloading PIDs to a Talon can save some CPU resources, which is not much, but it also can run PIDs much much faster than the RoboRIO (20hz vs 1000hz) (correct me if I'm wrong, I actually want to know the correct numbers)

[Greg McKaskle]

I think your PID loop will generally be limited by how often you can update your motor controller. For PWM, that is every 5ms for newer ones, 10ms for some older ones. CAN may be used to do faster updates.

The calculations are small by comparison. Of course you may not need to run your loop even that fast. It depends on the inertia of your system, the torque or force of the actuator, the lag of the sensor, etc.

Anyway, my point is that the 20ms is not a technical limit of the cRIO or roboRIO, but may be the default of the library you are using.

Greg McKaskle

[adciv]

While we haven't been testing CAN motor controllers under the beta system, we have used it with the PDP and PCM. I think you should forget about past experiences with CAN. Under the new system, it is EASY. I've been able to trivially add/remove a 2nd PCM on CAN. There really is no comparison between these new components and the troubles we've had trying to use JAGs in prior years.

Other thoughts:
- Even if you don't use the PID on the Talon SRX, you get the simpler CANBUS wiring if you use it over CAN.
- You can still control the Talon SRX over PWM and change to CAN next year.
- We've used PID over PWM for several years and 20ms is a faster rate than we've needed to run our control loops at, so don't worry about the differences in update rates.

[Monochron]

Originally Posted by Qbot2640

We always use pneumatics for something, but we have always used 12 volt solenoids with Spike relays. Can we no longer do that?

TO my understanding it is required that you use the new PCM to run your pneumatics. The PCM only communicates via CAN, so you will have to use it. Like others have said there, it isn't a large undertaking to setup CAN, just make sure you understand all the differences.

[FrankJ]

While controlling the compressor through the PCM will almost certainly be required, no reason not to allow the solenoids to be controlled by a Spike. Of course those who really know aren't talking. And no I don't have any special knowledge

[Jon Stratis]

Originally Posted by Qbot2640

We always use pneumatics for something, but we have always used 12 volt solenoids with Spike relays. Can we no longer do that?

That, unfortunately, is a rules question, and none of us know yet for sure.

However, the new PCM is pretty awesome and easy to use. It completely controls the compressor for you, with no coding needed - you just plug it and the pressure switch into the PCM and you're good to go. Additionally, you can control 8 solenoids (4 double solenoids) from each PCM, which would otherwise require 4 spike's - 1 PCM is smaller and lighter than 4 spikes.

While it's speculation at this point, I would assume that FIRST will require at least the compressor and pressure switch to be hooked up through the PCM.

[Qbot2640]

Originally Posted by Jon Stratis

... Additionally, you can control 8 solenoids (4 double solenoids) from each PCM, which would otherwise require 4 spike's - 1 PCM is smaller and lighter than 4 spikes.

Is this true? The information I read stated that the PCM replaced the spike for the compressor - but I did not think it would replace the individual solenoid spikes. If this is the case, then I am totally sold on the idea...saving all the spike space PLUS $30 a spike is major. Someone please confirm!

[Jon Stratis]

Originally Posted by Qbot2640

Is this true? The information I read stated that the PCM replaced the spike for the compressor - but I did not think it would replace the individual solenoid spikes. If this is the case, then I am totally sold on the idea...saving all the spike space PLUS $30 a spike is major. Someone please confirm!

We're a beta team, and an Alpha team before that... We've been controlling solenoids from the PCM for over a year now! The PCM is designed to control either 12 or 24V solenoids through a selectable jumper... it serves a similar purpose as the old pneumatics breakout board/module for the cRIO when it comes to solenoids.

[adciv]

Here's the full capabilities of the PCM
*It powers the Compressor
*You plug the 120 PSI Switch into it
*It controls 8 different solenoids. (Solenoids can be 12v or 24v, but must all be the same)
*You can have many PCMs on the robot

[MrRoboSteve]

Originally Posted by adciv

Here's the full capabilities of the PCM
*It powers the Compressor...

Powers the compressor, or controls a Spike that powers the compressor?

[Knufire]

Originally Posted by MrRoboSteve

Powers the compressor, or controls a Spike that powers the compressor?

It powers the compressor directly AFAIK.

[Mark McLeod]

Originally Posted by MrRoboSteve

Powers the compressor, or controls a Spike that powers the compressor?

Originally Posted by Knufire

It powers the compressor directly AFAIK.

Yes, Spikes no longer power the compressor.
It wires directly into the PCM.

[Gregor]

Originally Posted by Knufire

It powers the compressor directly AFAIK.

Correct. There's a dedicated port from the PDP to the PCM, from which the compressor is wired.

[cgmv123]

Originally Posted by Knufire

It powers the compressor directly AFAIK.

Yep, the compressor +12v and ground wires plug straight into the PCM. There's some very intelligent circuitry in the PCM to make sure the large start current required by the compressor or any potential shorts in the system doesn't blow the fuse on the PDB's control system supplies. (The solenoid outputs have the same protection.)