New Speed Controllers :)

[Richard Wallace]

Originally Posted by sparksandtabs

draining 120A continously will COMPLETELY drain your battery in 9 minutes flat. ...

Actually, much quicker than that.

See the battery datasheet and this thread.

[John Gutmann]

well anyway why would they let you use 120A continuously if they can just step up to the old 883's that run up to 60A continuously. I think that is more acceptable, plus you dont have to use practically a solid copper rod for a wire.

[Tom Bottiglieri]

Originally Posted by sparksandtabs

well anyway why would they let you use 120A continuously if they can just step up to the old 883's that run up to 60A continuously. I think that is more acceptable, plus you dont have to use practically a solid copper rod for a wire.

Unless you are straining 10 motors, there is no reason you should EVER get anywhere near 120A continuous current draw. Not to mention your batteries would bite the dust quite quickly with that kind of abuse.

By the way, you would be much better off using thick stranded wire than one solid piece of wire. Current flows on the surface of a conductor, so the amount of current a single piece of wire can transmit is limited by its size.

[Richard Wallace]

Originally Posted by Tom Bottiglieri

By the way, you would be much better off using thick stranded wire than one solid piece of wire. Current flows on the surface of a conductor, so the amount of current a single piece of wire can transmit is limited by its size.

Only the alternating component of electrical current tends to concentrate on the surface of a conductor. This is often called the skin effect. The effective depth to which current penetrates into the interior is inversely proportional to the square-root of the frequency at which the current alternates, so higher frequency current tends to concentrate on the surface, while dc is uniformly distributed over the cross-section of the conductor.

Since only a small component of the motor current in a FIRST robot is ac (due to the pulse-width modulation of the Victors), using stranded wire does not improve the current carrying capacity significantly over that of solid conductors with the same total cross section; i.e., the same AWG.

However, using stranded wire is still a good idea because it is less prone to damage from bending and flexing, and it forms better electrical connections when crimped to standard terminals.

[BrianBSL]

Are these actually new? I was pretty sure the 885's have been out for a while now. Maybe I'm just confusing myself though.

[Billfred]

Originally Posted by BrianBSL

Are these actually new? I was pretty sure the 885's have been out for a while now. Maybe I'm just confusing myself though.

I can't place a date or anything, but I know that the 885s have been available since at least last off-season.

[John Gutmann]

Originally Posted by Tom Bottiglieri

By the way, you would be much better off using thick stranded wire than one solid piece of wire. Current flows on the surface of a conductor, so the amount of current a single piece of wire can transmit is limited by its size.

By the way I know that, it was sarcasm because to run 120A through 1 wire you would need 0 gauge wire. which is about 1/2" in daiamter.

I can't even Imagine trying to run wires like that to a motor.

Besides you can really draw more current then the wire already on the motor will allow(if any), like the CIMs with out modifying it. Or if there is no wire you would have to go by cantact area, and the other motors dont have a big contact area.

[lukevanoort]

I really don't see these being used in FRC anytime soon, they're just too powerful. The price for a V885 is higher and the motors would be ungodly, an example of the type of motor these are for is the PERM PMG 132, it can pull 110A constant, it costs almost one thousand dollars! That is way to pricey for FIRST. Instead, I would also, like Gdeaver, like to see a little more computing in the 884. Maybe a just single, low-end PIC (although it might need shielding), some sort of sensing to keep you from frying it from wiring the inputs backwards, maybe a lower profile fan, and an improved PWM slot. (maybe like the old ones with just pins, then add a clip on the top to hold it in place) It could be the Victor 884-Xtreme (or 886), some cheap 20A speed controllers for the weaker motors would be nice too... (Maybe it's time for IFI to plunge into the Hobbyweight battle bot market with low current speed controllers, maybe name them the Rufus series)

[Andrew Blair]

Originally Posted by lukevanoort

some sort of sensing to keep you from frying it from wiring the inputs backwards

I can't believe it's not already there. That would be a great improvement.

Originally Posted by lukevanoort

and an improved PWM slot. (maybe like the old ones with just pins, then add a clip on the top to hold it in place)

Like these?

I like that too. http://www.robotmarketplace.com/mark...e_ifi_esc.html