*Warning* On talons!!!!

[dyanoshak]

Emphasis on can damage.

I have personally caused a Jaguar failure by connecting a dead short across the motor terminals. This was in early Jaguar testing 3-4 years ago.

I haven't personally caused a failure with the others.

Scott and I aren't implying that certain exact conditions will or will not damage any of the motor controllers. We're trying stop a common misconception that the breakers instantaneously trip once you go over 40A. They take time, and can't be guaranteed to protect anything but the wiring.

-David

[Ether]

Originally Posted by dyanoshak

Scott and I aren't implying that certain exact conditions will or will not damage any of the motor controllers. We're trying stop a common misconception that the breakers instantaneously trip once you go over 40A. They take time, and can't be guaranteed to protect anything but the wiring.

Understood. But there's a flip side to that coin, to wit:

Assuming the datasheet specs for the 40 amp breaker can be trusted, it's possible to design a product around those specs so that the breaker WILL protect it.

Hence the question: what are the chances of damaging, say, a Talon, if it is properly wired and protected by a properly operating in-spec 40 amp FRC breaker?

I wouldn't lose any sleep over it.

[apalrd]

Just some random subjective data, but we've been running fanless Talons in our prototype drivetrain for many weeks now stopping to change batteries and the talons are hardly warmer than ambient to the touch. This is with 4 CIMs and 40a breakers and a ~120lb total robot weight incl. battery (so a bit light) on carpet geared fairly aggressively. I would begin to worry about heating the battery cable and CIMs before I worry about warm talons.

A CIM in a drivetrain will pull full stall current immediately at launch. It will taper down to a much lower level very very quickly, how quickly is dependent on gearing, mass to accelerate, and voltage drop.

Use fans if you want. Think of them as speed controller insurance with a 20 gram weight penalty.

[Ether]

Originally Posted by apalrd

geared fairly aggressively

what does "geared aggressively" mean in this context?

[apalrd]

Originally Posted by Ether

what does "geared aggressively" mean in this context?

We gear our prototypes for high speed because we are interested in high-speed behavior and know that low gear behavior will always be better than high-gear behavior.

This particular one was estimated to travel around 13fps after estimated losses. We don't have any sensors on it to test this, so I can't verify, but it is going somewhere in the neighborhood of that speed, with 4x CIM power.

This particular chassis tends to eat a battery every ~7mins. That's not all hard driving, there's some argument over dynamic performance behaviors and some calibration going on at the same time. About 5mins of actually driving. We change the battery when the radio reboots (we're running the radio to the 5v camera supply, not the nice regulated supply).

[fox46]

I have a feeling someone just looked at the motor spec sheet and a talon spec sheet and concluded they would not work together.... which is incorrect.

Generally, electrical components fail in some shape or form because of heat. If you draw too much power through them, things get hot and their physical/electrical construction degrades rendering them non-functional. This sometimes results in all the magic smoke leaking out

Every time you pass current through a conductor it generates a small amount of heat. When the component is operating within its specifications, it is capable of dissapating said heat as fast or faster than it is generated. When you exceed the current ratings, the component will continue to function until it becomes overwhelmed by the temperature and burns out. So you can indeed exceed the capacity of the device for short periods of time but if you exceed its ability to keep cool, you'll ultimately shorten its life drastically or burn it out. This also translates to why speed controllers with fans are more hearty than those without.