Talon SRX Motor Controller Problem
 

We have a problem connecting the motor controller to the PWM ports on the roboRIO. We believe to have correctly connected the motor controller to the roboRIO and the Power Distribution Module. When we connect the motor controller to the CAN port, the motor controller works. However, when we use the PWM ports, the motor controller doesn't work and just blinks red.

We took two photos of the system which are posted below.

Thanks for any help!

Re: Talon SRX Motor Controller Problem
 

To use PWM, you need to flash the SRX using a different firmware. See section 1.3.4.2. PWM – Updating firmware for PWM use in the SRX's User Manual.

Re: Talon SRX Motor Controller Problem
 

That section explains that PWM CAL Mode and Limit Switches require the upgrade. General PWM drive does not require the update, however it is required to be FRC legal if the firmware is <0.28.

Your photo looks like the green wire is connected to the middle pin, which is not correct. Green should go to ground. See Section 1.3.3 of the Talon SRX User's Guide.

Re: Talon SRX Motor Controller Problem
 

Why are you attempting to run the SRXs from PWM anyway?

Re: Talon SRX Motor Controller Problem
 

Neither of our wires are connected to the middle pin - the green is connected to ground. By our understanding, the problem with the CAN wires is that they employ series circuiting rather than parallel. So if one of the motor controllers goes out, then the others stop working. This is the reason we are trying to use PWM ports, but correct us if we wrong about this.

Thanks,
Charging Champions

Re: Talon SRX Motor Controller Problem
 

Supposedly, both pairs of Talon SRX wires are continuous with each other. You should also note that if you use PWM, you don't get any of the nice PID and active brake and coast switching features.

Re: Talon SRX Motor Controller Problem
 

+1

For most teams that use Talon SRX's, the main reason is the built-in PID and active breaking software, which is only available via CAN. Obviously you already have these Talon SRX's, but in the future if you know you will only be using PWM you can buy cheaper motor controllers that do effectively the same thing. You can get SPARK motor controllers from REV Robotics for $45 (half the price of a Talon SRX). If you really need the small package, you can get Victor SP's ($60 IIRC). Of course this isn't to say that the Talon SRX's won't work with PWM, just that in the future there are cheaper alternatives.

Re: Talon SRX Motor Controller Problem
 

+1 to that too

Also, you should put some form of connector on your wires. It's possible you were shorting +5v to ground with your current setup. If you don't have the proper connectors and crimper, you can solder the wires to a preexisting PWM cable. Using connectors will also give you something good to attach the cables with if you decide to use CAN at some point, since I doubt you'll want to cut, restrip, and solder the wires every season, especially since the wires are permanently stuck to the controller.

Re: Talon SRX Motor Controller Problem
 

Thank you all for the replies. A couple of questions:

1. So if we used the CAN ports, which don't use parallel circuiting, would it be right to say that if one motor controller were to stop receiving power, then the rest of them would not receive any inputs through the CAN wires?

2. Should we use Anderson Powerpoles to link together CAN wires or a different mechanism? What is the cleanest way of linking CAN wires?

We are probably going to stick with the CAN ports.

Thanks for the help,
Charging Champions

Re: Talon SRX Motor Controller Problem
 

1. I believe the input and output CAN wires on a talon are soldered to the same place. So even if one motor controller were to lose power, the rest should still work. ( Someone correct me if I'm wrong). Also, it is really rare that only one of your motor controllers should lose power, especially if the wiring was done correctly.

2. We always cut our CAN wires to the exact length and solder them together and cover in heatshrink. Makes really clean runs. If we need more length on one wire later on, we can always just solder on more wire, or if it comes to it, take apart the motor controller housing and compltley swap out the wire (it's not too hard).

Re: Talon SRX Motor Controller Problem
 

We used CTR's CAN Connector Pack to connect our SRXs this year. They worked great, just put some electrical tape over the exposed solder points on the bottom (just in case). Makes it very simple to re wire the CAN network (as we had to do as we needed more motor controllers suddenly), and means you don't risk damaging the cables much with other connectors. It uses the same connectors as on the PDP, PCM and roboRIO. It may not be the cleanest way (our board was not very clean this year), but it certainly makes it easy to change later. Anderson connectors would be cleaner cut to the right length, but for the CAN wires, these connectors are overkill. Try .1" pitch PWM wires maybe instead?

And as Rohit said, most CAN devices just connect high-high and low-low and just take that signal elsewhere for processing. Also, you don't have much probability of one dying on you. Though more likely, if one died your code would crash as it couldn't initialize the CANTalon anymore. That's assuming the entire thing just died rather than the just the voltage controlling circuitry, which is more likely. The SRX is advanced enough to have current limiting and the such, and because of that I've never seen a dead one.

Re: Talon SRX Motor Controller Problem
 

A breaker trip will cause a single controller to lose power.

As others have noted though, the controller losing power will not interrupt your CAN chain.

This should not crash WPILib code, it will just throw errors into the log.

Re: Talon SRX Motor Controller Problem
 

For connecting CAN wires, I would recommend using the DuPont 3 pin connectors, since they can also then be used for PWM if you want. You can also use Wago lever nuts, since they can be reused very easily and don't require special tools.

Re: Talon SRX Motor Controller Problem
 

Thank you all for your help. Currently we have a CAN wire running from the RoboRio to a central "hub". CAN wires from each motor controller are connected to this "hub" (see image below). They are currently secured with electrical tape - we are planning on using a more substantial connection (based on the suggestion you guys provided. Does this setup look right?

Also, how do we know if the Talon SRXs are connected to each and working? Do they alternate orange?

Thanks once again.

- Charging Champions

Re: Talon SRX Motor Controller Problem
 

Electrical tape is a bad idea, but you already knew that. There are many solutions here, use one of them. Also, while I believe this setup may work, I'm not sure it's you best option. Your best option is to connect the green of one to the green of another, like you see in the SRX manual. And yes, if they are properly connected but not enabled, they will alternate orange. They will alternate red if they cannot connect. Once enabled (and initialized in code), they will stay solid orange and then flash the color of the direct they are going, like the other motor controllers.