Jaguars and Talons

[FS Robotics]

Originally Posted by Ether

Not analogous.

Are you saying Victors and Talons are compatible? We have two victors and two talons (only one jag, that was a mistake). Would having half Victors and half Talons cause issues?

[nuggetsyl]

Originally Posted by Ether

Not analogous.

And now 90% of the students are looking up the definition of analogous.

Talons and jags were built to do different things. Just like street tires and snow tires were built for different tasks. Sure they will drive your car but are they best suited for the task together?

[Ether]

Originally Posted by nuggetsyl

Talons and jags were built to do different things.

They were both built to control the voltage applied to brushed DC motors.

They both use the same switching method and the same switching frequency.

Let's explore this together. What do you think would be some of the possible problems with controlling a 2-CIM gearbox open-loop with one Talon and one Jag, on each side of a skid-steer bot?

[Ether]

Originally Posted by FS Robotics

Are you saying Victors and Talons are compatible?

No. Not saying that.

I am searching for the source (hard data or well-reasoned theoretical considerations) of the apparent conventional wisdom that Jags and Talons are never compatible in any application.

We have two victors and two talons (only one jag, that was a mistake). Would having half Victors and half Talons cause issues?

I think that's a question worth discussing (and possibly testing). I wouldn't recommend risking your 2014 season on it.

[Rynocorn]

Originally Posted by Ether

Unless you swapped the two left-side Vics with the two right-side ones and observed that the problem switched sides, you can't conclude that the turning was caused by a difference in the Vics.

We replaced all of the victors today with all 888s and no other changes and it is working perfectly now so unless we didn't have something screwed in tight then it probably was that as we are driving perfect now. I'm not sure though

[kevin.li.rit]

Originally Posted by Ether

No. Not saying that.

I am searching for the source (hard data or well-reasoned theoretical considerations) of the apparent conventional wisdom that Jags and Talons are never compatible in any application.



I think that's a question worth discussing (and possibly testing). I wouldn't recommend risking your 2014 season on it.

I'm willing to try 1 Victor 888, 1 Talon on each side of my drivetrain. I really don't see a problem in doing it. What kind of measurements should I try and take?

[yash101]

Originally Posted by geomapguy

Hmmm good point. I just always assumed it was just bad practice.

SO does it have much effect???

The effect would be neglegible. However, the different handling of motor controllers means that one motor would go through much more abrasion than the other.

While there are safety diodes, one motor may generate enough backflow because of reverse electro-motiv force, to destroy MOSFETs on these motor controllers. However, this is typically negligible!

It's funny how basic physics can explain so much . #ILovePhysics

[kevin.li.rit]

Originally Posted by yash101

The effect would be neglegible. However, the different handling of motor controllers means that one motor would go through much more abrasion than the other.

While there are safety diodes, one motor may generate enough backflow because of reverse electro-motiv force, to destroy MOSFETs on these motor controllers. However, this is typically negligible!

It's funny how basic physics can explain so much . #ILovePhysics

How would one motor go through much more abrasion?

[yash101]

Originally Posted by kevin.li.rit

How would one motor go through much more abrasion?

It won't be pushing as much, so one motor will have to work harder to speed the other slacker up

[kevin.li.rit]

Originally Posted by yash101

It won't be pushing as much, so one motor will have to work harder to speed the other slacker up

Okay, but in this situation the motors are mechanically linked and spinning at the same speed, so how much does this difference in voltage/current cause much more abrasion?

[Ether]

Originally Posted by kevin.li.rit

I'm willing to try 1 Victor 888, 1 Talon on each side of my drivetrain. I really don't see a problem in doing it. What kind of measurements should I try and take?

Skidsteer drivetrain, with 2 gearboxes with one Vic and one Talon per gearbox?

Or four gearboxes with one motor per gearbox?

Assuming the former, here are some ideas, in no particular order:

Just drive it around and see if it behaves normally. No weird noises or odd behavior.

If everything seems OK, do hi speed, lo speed, pushing, turning, reverse, fast throttle changes, etc.

Feel both motors on both sides and see if there's a noticeable difference in temperature (e.g. are both Vic-driven motors hotter than their Talon mates, or vice-versa).

If you can instrument your bot to measure current, that would be excellent, but may be more work than you have time for.

[Ether]

It won't be pushing as much, so one motor will have to work harder to speed the other slacker up

This happens all the time. All motors are not created equal. Neither are all motor controllers.

[magnets]

Originally Posted by yash101

While there are safety diodes, one motor may generate enough backflow because of reverse electro-motiv force, to destroy MOSFETs on these motor controllers. However, this is typically negligible!

It's funny how basic physics can explain so much . #ILovePhysics

Not quite. There are NO DIODES (on the outputs) on the controllers we use. The diodes would waste roughly 10% of the power by dissipating it as heat.

Also, the MOSFETs are set up so that if the robot is off, and you push it along, the power goes back and powers on the robot, no harm done. If you run while pushing the robot, you can get the cRIO to turn on.

[kevin.li.rit]

We're planning on a skid steer. 1 gearbox on eachside.

[kevin.li.rit]

Originally Posted by Ether

This happens all the time. All motors are not created equal. Neither are all motor controllers.

I was thinking the same thing.