Victor 888 vs Jaguar for rookie drive train

Technical Electrical
#6

It seems like there might be a couple misperceptions here. The Kitbot on Steroids was developed with the 2011 kitbot in mind. Since then, the rules restricting robot size have changed (robots are smaller now). Also, the kitbot will be quite different this year from previous years (as per the FRC blog). Most of these changes are for the better, but it does mean that the Kitbot on Steroids isn’t necessarily legal for this season and it’s features may not directly apply to this years kitbot. However, many of the concepts in KBoS, like the electronics board and changes with the wheels can still likely be adapted to this year’s kitbot to help you improve your drive base. It’s awesome that you are looking to Kitbot on Steroids for inspiration, just want to make sure you’re aware that the exact design isn’t necessarily legal for this season.

As for jaguars vs. victors, I agree with RC and Brennon that victor 888’s will be the more reliable option for you. However, it’s not that there is ‘no use’ in using jaguars if you don’t use CAN. Jaguars will also work on PWM, but they are heavier, have a larger footprint, and are less robust than victors. So the jaguar you get in the kit isn’t ‘no use’ because you choose not to use CAN (I support this choice by the way), but I would suggest that any additional motor controllers you get be victor 888’s or talons.

#7

We are aware that the rules according to size will change. We are just using the basic principals of the kitbot on steroids, the wheels, chain drive and 4 motors, in our build. We will adapt those ideas into whatever size there will be for the 2014 season.

As of the motor controllers I am aware that Jaguars can use PWM. We have a loaner bot that we are messing around with and that has 4 Jaguars on it. I was trying to say that one of the main advantages of Jaguars was that you could use CAN, and because we arent doing that it would be logical to use the lighter and smaller Victors.

#8

Keep in mind that any assuming of what the rules will be will only make an…well you know. As a rookie team make sure that the first thing you all do after the kickoff and extra videos are over is to ::rtm:: ::rtm:: ::rtm:: . Yes three times is the charm as far as day one is concerned then many more rereads need to be in order. :smiley:
As far as the motor controllers go I would recommend the 888s. They are very reliable and from our team’s past experience they have been more robust than the jags. Some examples of this would be PWM’s falling out on jags and not 888’s as well as exposure to metal shavings and overheating have occurred more often to our jags. The only problem our team ever had with the 888’s was when we didn’t set the PWM cable into the port correctly.

#9

Victor 888: the rookies best friend! We used them this year on our drive and loved them, the Victor is also smaller from a mounting point of view than the Jaguar, making it easier to fit everything as rookies. Apparently the Victor is also used in some cases for battle robots, if they can count on them for that then they must be doing somthing right.

#10

As Brennon pointed out, you may like the victors. They are a great choice. However, if you get good funding (because you are a rookie team), you may want to give talons a try. It works exactly the same as victors (even the wiring) but is sealed, so you won’t have to worry as much as debris getting inside the holes, damaging the controller :wink:

I think that victors are the best for rookies because PWM is a very easy-to-use motor communications protocol. You probably will have access to only one cRIO, so the team will be cramped trying to use it for educational purposes. With PWM, you could easily use an Arduino or Propeller, etc. That way, you could prototype an application by yourself while another person can be using the cRIO or another controller.

I really like how easy it is to use PWM. However, this would be one-sided because I haven’t played much with CAN!

However, if I am not wrong (and please correct me if I am), you can have more motor controllers on the CAN but than you can have PWM connections. That will allow you to have more complex mechanisms! There is the problem that it is hard to get enough Digital I/O pins.
“Pins, pins and pins…what microcontrollers need more of”

Check out this thread

#11

Even with the PWM cable properly secured in the cable retainer??

as well as exposure to metal shavings

My understanding is that the VEX Jag PCBs are are conformally coated.

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Jag cable retainer.png
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Jag cable retainer.png
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#12

I’ve always been a fan of Jaguars due to easy for rookies to use (not calibration, easy to stick the pwm cables in). Just my $.02

#13

Concur with the choice of Victor 888s vice Jags for simple motor controller. Jags are best used for CAN control and sensor integration (ie plugging sensors directly into the Jag).

Limit switches is a great use for Jags. Limit switches can be connected directly into a Jag. When the switch is pressed while the motor is moving in its direction, the Jag stops the motor, independent of the cRio software control. This is a good safety control when going beyond the limit switch can damage the robot wiring, etc. This limit switch mode works in both CAN and PWM control setups.

Jags can also accept encoder and pot inputs and can provide that data to the cRio via CAN control. There is also the automated feedback loop control.

#14

Besides reliability and price, another great thing about Victors is that they have a much smaller footprint than Jags. Especially since the robot size has been reduced in FRC last year, teams are struggling to find room for electronics (especially young teams like yours and mine). The victors are a huge help for this.

#15

We found the Victors to be more reliable than the Jags, but as was mentioned, the Jags are great when you need to use limit switches.

Also, you may want to look at the IFI PDV more closely. You will get to choose one of the following options:

  • Two Jags
  • Two Victors
  • One Jag & One Victor

The IFI PDV doesn’t allow you to get two more of each.

As far as drive train goes we used the Victors on our bot last year and they worked great. Controlled the motors well and we had no issues with failure of drop outs of any kind.

Good luck this year. If you need any help don’t hesitate to ask. The folks here are a great resource for a rookie team.

#16

The thing to take away from the kitbot on steroids to apply to the 2014 kitobot is to use 4 motors. The new chassis will be using belts like the 2013 chassis and will direct drive the center wheel. Belts are ready to go out of the box and were proven in competition last season. Switching it to chains would be counter productive as they add weight and coming up with the parts necessary to convert it will likely mean some fabrication, and waiting for parts to do so.

Do yourself a favor and put the kit bot together in one of the configurations that the instructions show you how to do. When your additional CIMS show up add them to your fully functioning chassis. Meanwhile have your electrical and programming team prepare for 4 motor drive just don’t install the breakers and pwm cables for the other two motors and controllers until you have them. In the mean time you can have a running and driving chassis and have drivers practicing.

With a small and new team your best use of time is to focus on the game piece manipulator.

#17

While important, there is a lot more to take away from it than that. Consider using high traction treaded wheels instead of Kit wheels for added resistance to pushing. Use a plywood electronics board in order to stiffen the chassis.

Belts are ready to go out of the box and were proven in competition last season. Switching it to chains would be counter productive as they add weight and coming up with the parts necessary to convert it will likely mean some fabrication, and waiting for parts to do so.

While the belts are more than fine, and if they work for you they should be used, chain isn’t bad either. You can definitely build a chain kitbot drive without fabricating anything (teams did that for YEARS), and chain does give you the ability to use different wheel spacings than the kit starts with. The tradeoff is that chain weighs more and requires tensioning.

With a small and new team your best use of time is to focus on the game piece manipulator.

Definitely. Find the easiest task with a high return on investment and excel at it.

#18

Max,
I prefer the IFI Victor solution over the Jags. While many will point to the lack of limit switch input, non-linear output, calibration and PWM retention as cons, all of these issues are easily overcome with other solutions. The Victor is a rugged little controller that you can continue to use for years to come and be happy with it. If you search out other posts here on CD you will find that the differences are relatively minor. The linearity for instance is more a function of switching frequency, calibration is needed for all controllers and PWM retention is easily overcome with tywraps or other cable management. I personally find the fault modes on the Jag troublesome for many teams. High load current, low input voltage and over temp can set the Jag into fault which disables the output for a few seconds after the fault is removed. The Jag does let you know (if you can see the LEDs) when it has entered fault mode. However, having one side fault while the other still drives makes for interesting driver response.

#19

What is alarming me, is that its sounding like you may intend to get along with only 4 or possibly 5 speed controllers total. This will almost assuredly not be enough. Even the simplest effective scoring machines using 4 drive motors I’ve seen in 10+ years of FRC have used a minimum of 5, and more commonly 6-8 speed controllers in total.

#20

Agreed,

Our bot from last year had 9 controllers.

(1) Jag - Tilter
(6) Victor - (4) Drive, (2) Shooter
(2) Vex Motor Controller 29 - (1) Slider, (1) Indexer

The Jag was great for our tilter because it allowed us to use the built-in limit switch connections to limit the amount of travel on the tilter.

#21

This is true, but you can have 20 different PWM outputs. No team will need 20 different outputs, so number of outputs isn’t really an issue.

Having lots of speed controllers is nice. Last year, we had 4 on drive, 1 shooter, one for climber deployment, and three for the climber for a total of eight.

#22

I’m pretty sure I count only 10 PWM outputs on the Digital Sidecar. Therefore, I’m assuming you’re referring to using two digital modules and two sidecars.

If you use the default setup, i.e. where a Black Jaguar is used as a Serial to CAN bridge, you max out at 16 CAN nodes (though multiple teams have posted that they had comm issues at 12 to 14 nodes). I’m unsure of the maximum for a 2CAN setup, but I believe that it should be higher.

Therefore, the protocol that can handle more nodes it is dependent on how many digital modules and sidecars you use (which in turn is partially based off of your model of cRIO – the older model had more slots available).

All of this being said, I tend to agree with magnets; the number of nodes you can control with either protocol is really not a factor in deciding what protocol a team will implement on their robot. And this is all completely tangential to the OP’s question, to which it sounds like they’d rather use Victors.

#23

That is true. However, when you have small things like servos and pneumatics (don’t they use PWM?), you will get quite cramped. I think we may have maxed out on our PWM capabilities. We didn’t want to do something funky like multiple DSes. But I guess that’s what happens when you want too many functions in a robot (Good shooter [until it broke] and a reliable climbing mechanism)

#24

http://www.andymark.com/v/vspfiles/photos/am-0866-2.jpg

Servos do take up one of your PWM ports. You also need to install a jumper to ensure correct voltage.

Pneumatics are not typically controlled via Digital Sidecar (though you can control them with relays). Teams generally use the Solenoid Breakout.

Relays don’t physically use the PWM ports on the DS. You can see in the picture that there 8 sets of relay pins below the PWM ports and in between the I2C port and Digital IO ports.

But let’s not hijack this thread; let’s get back to answering the OP’s question, not answering various side questions about how many PWM connections you can make or how cramped the DS gets. That’s the subject of a different thread.

#25

Rookie teams also get 2 Victors and 1 Jag in their Kit of Parts.

See here: http://www.usfirst.org/sites/default/files/uploadedFiles/Robotics_Programs/FRC/Game_and_Season__Info/2014/Rookie_Veteran_Variation_Table.pdf