New Speed Controllers :)

[Alan Anderson]

The Victor 885 is intended for 24 volt applications.

[Richard Wallace]

Originally Posted by Alan Anderson

The Victor 885 is intended for 24 volt applications.

Originally Posted by Victor 885 Speed Controller Specifications

Control Signal Standard R/C Type PWM (Pulse Width Modulation)
Operating Voltage 6V to 30V (does not include the fan)
Fan Type Rotron. Battle proven by Inertia Labs (and many others).
12V Fan Voltage 6V to 16V
24V Fan Voltage 16V to 30V
Maximum Current 120A continuous
Surge Current 200A for < 2 second
300A for < 1 second
Power Connector 6-32 Screw Terminals
Signal Connector Use a standard non-shrouded PWM cable (3 wires)
Typical Application Power one motor with variable speed forward, reverse, or off
Weight 0.25 lbs

Seems like you could use it at 12V since it's rated for operation at 6V.

Anyway, as long as we're using 40A snap action breakers on each circuit, the capability of the 885 won't be exploited. We'd get a small benefit in reduced voltage drop. For FRC use that doesn't seem worth the difference in price.

885s seem to be intended for big bots. 24V x 120A is 2880 Watts; at about 75% efficiency that would be about 3 HP at the motor shaft. Way too much power for a FIRST robot, even if we were to get motors that could handle it.

[Gdeaver]

They cost to much. I would rather see some programmability in the speed controllers. Like current limiting, current feedback and protection circuitry. Also maybe a small cheaper ESC for the window motors and van door motor. International rectifier has allot of new automotive stuff with some reference designs that could be Incorporated into First robot motor control. If we had intelligent speed controllers, the 2005 Fisher Price motor problem could have been solved at the speed controller. While servo pwm has worked well, maybe its time to think about going to a motor control bust or something.

[d.courtney]

who says we are even going to have carpet next year (my vote(and hopes) is on water... )

[Rohith Surampudi]

Originally Posted by d.courtney

who says we are even going to have carpet next year (my vote(and hopes) is on water... )

there could be wet carpet...or a pool and for some reason it would have carpet on its floor

[Pavan Dave]

Originally Posted by Richard

Seems like you could use it at 12V since it's rated for operation at 6V.

Anyway, as long as we're using 40A snap action breakers on each circuit, the capability of the 885 won't be exploited. We'd get a small benefit in reduced voltage drop. For FRC use that doesn't seem worth the difference in price.

885s seem to be intended for big bots. 24V x 120A is 2880 Watts; at about 75% efficiency that would be about 3 HP at the motor shaft. Way too much power for a FIRST robot, even if we were to get motors that could handle it.

Yep. Your absolutely correct. There is no way that we need that much power on the field unless FIRST was taking a turn for the worst turing it into BattleBots.. (Thank god its not)



Pavan

[John Gutmann]

draining 120A continously will COMPLETELY drain your battery in 9 minutes flat. SO think about it if you have 2 motors (probally drive) running around 120. you battery will completey be drained in 4.5 minutes. Not to mention everything else your running. This means (estimate only) that by the end of the match your battery would be around 6-7 volts maybe. do you really wanna drain your batteries that fast? Besides doesn't that ruin them?

[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)