Victor 888: Upgrade to the Victor 884
 

I was just looking at the VEX site, planning to buy some spare 884's, and I noticed this message on the page:

"A new and improved version of the Victor 884, the Victor 888, will be available Thanksgiving 2012. The Victor 888 will include a linearized output."

http://www.vexrobotics.com/products/...ontroller.html

Anybody have any inside information? Sounds like a nice improvement to the 884's, and removes the need to linearize the output via code.

Maybe wishful thinking, but it would be nice to hear if they are going to be FRC legal for the 2013 game sometime before January 5th.

Re: Victor 888: Upgrade to the Victor 884
 

There is also new the Talon controller from cross road electronics that was talked about at IRI.

Re: Victor 888: Upgrade to the Victor 884
 

Hmmm, wonder if there is a connection there?

A family connection :)

Re: Victor 888: Upgrade to the Victor 884
 

I hope they reduce the price or introduce a cheaper speed controller in the 20Amp range.

I'm tired of paying $90 for a product that was created 10 years ago.

Re: Victor 888: Upgrade to the Victor 884
 

I'm really hoping the talon become legal for use. From the limited time I had looking at it, it seemed a really high quality product.

Re: Victor 888: Upgrade to the Victor 884
 

Our lead Mentor picked up a cut sheet on the Talon at IRI. Info that was listed.
15khz switching frequency, 100 amp max, 60 amp continuous, 800 micro- ohm per leg, lock anti-phase rectification.
The Talon departs from the Victor and Jag by using a heat sink and optional fan.
I would suggest that they not say anything about a fan being optional and just put a fan on it powered all the time. There are some graphs of time, current and temperature. No info on the specifics of the test set up for the graphs. They also show a linear response. IFI has modified the Victor to have a linear response. I understand they are doing it in software. Is the Talon linear because off the 15khz switching frequency? Can the Talon hold up to First abuse? Time will tell. Whats the price? Will the Talon because of the switching frequency have problems with the window motors like the jag? If Cross the road would get some to us we would being willing to beat the hell out of them this fall.

Re: Victor 888: Upgrade to the Victor 884
 

If I remember correctly, there was a number of teams running the Talon motor controller at IRI and it seemed well up to the challenge. Perhaps they can speak up here.

I spent some time at their booth talking to them about it. Besides the linear output another nice feature was a tighter fit on the pwm cable (I saw them lift the controller while it was powered up by the pwn cable)

The heat sink looked nice and seemed to go further with protecting the internals of the unit, and it still retained mounting holes for a standard fan.

Re: Victor 888: Upgrade to the Victor 884
 

Does it also work with CAN?

Re: Victor 888: Upgrade to the Victor 884
 

Negative. At least, I didn't see any CAN ports on the unit at IRI.

Re: Victor 888: Upgrade to the Victor 884
 

If the fan came with the Talon then it's use would be mandated, if FIRST decides to make it legal. Having the fan separate would allow teams to only use the fan when necessary thus allowing for a lighter design. Each fan weighs 16 grams, ten fans = 160 grams or .35 lbs. Teams would now have yet another way to "Trim fat".

The test setup can be found in the user manual.
www.crosstheroadelectronics.com/Talon


Which problem are you referring to?

Re: Victor 888: Upgrade to the Victor 884
 

This version of the Talon does not support CAN.

Re: Victor 888: Upgrade to the Victor 884
 

Re: Victor 888: Upgrade to the Victor 884
 

This would not reduce the cost any significant amount. The only difference between a 20 amp design and a 40 amp design is the choice of FET's. A Fet with a lower continuous drain current would most likely have a higher Rds on(drain source resistance). This would cause more heat rise/power dissipation than a higher current device. The cost to assemble, test and the part count does not change. Your $90 controller would become maybe $85. I think the 5 bucks is worth the extra efficiency and power.

Re: Victor 888: Upgrade to the Victor 884
 

From the posted information:

Any Debris that does enter the housing won't get past the conformal coating that protects the surface mount components.

A conformal coating on the the PCB! Now that's a huge step in the right direction for FRC motor controllers where metal shavings always seem to find their way into motor controllers.

Re: Victor 888: Upgrade to the Victor 884
 

Oh that problem. That was the PTC. We have used Jags on our window motors since 2009 and have never seen a problem like this that was not caused by the PTC. Also I would like to correct some factual errors in that post.

The poster describes the output of the Jag to be switching between +12 and -12 volts. This type of rectification is known as locked anti-phase. Both the Victor and the Jaguar use a type of rectification called sign-magnitude. Although both motor controllers use the same type of rectification the Jaguar Does whats known as synchronous sign-magnitude rectification.

During the off period of the duty cycle the Victor allows the free wheeling current(opposite of the forward current) of the motor to return through the body diode of the FET's. The diode has a forward voltage drop of about 1 volt regardless of the current passing through it. Since Power = I x V if 20 amps of current is passing through the body diode, then the power being dissipated in the FET is 20 watts (1volt x 20 Amps). This causes heat rise and losses to accumulate in the Victor.

The Jaguar does something a little different, during the off period the jaguar switches the opposing low side FET on thus connecting the motor leads together, the freewheeling current is now passing through the drain source junction of the FET's rather than the body diode. Since the FET's have a very low drain source resistance (say 2 mOhms) the power dissipated by the FET's is = to (I*I)*r the power dissipated is .8 watts. What does this mean? Well basically more power is being dissipated in the motor windings instead of the FET's. This is probably what is causing the PTC to over heat and trip. However what it really means is that the window motor is being over driven. Moving it to a Victor allows a slower decay of the free wheeling current thus decreasing the heat dissipated by the motor.

So the problem has nothing to do with the switching frequency and more to do with the type of rectification. I would suspect in this example the Victor was actually providing less power than the Jag possibly due to calibration differences. Both devices use different PWM input values so it is possible that the Victor may not have been delivering full power. Another thing to remember is that at full power both devices are full on so switching has no affect. This could also be a contributing factor since the Victor is not linear, the same PWM value will yield a very different output.

Re: Victor 888: Upgrade to the Victor 884
 

The window motor thermal shut down with the locking pins removed and a jag was only seen when used in a positioning application controlled by a PID. We used the window motors for our swerve steering - 4 wheel independent continuous rotation. With the jag we had intermittent thermal shut down with the jag. We switched to victors and had no more problems even with extended run times during practices in a hot building in the summer. We have used the window motors in other non - positional applications and not had problems with the jags. Of course if the window motor is over loaded it will shut down with any controller. It will live to run again. For what ever the reason jags and window motor in positional applications is probably not a good idea. We have used the banesbot motor and transmission for 2011 and 2012 avoiding this problem.
Did you find that the output of the Talon was linear or did you have correct it in software?
There have been many versions of the jag. I'm almost certain one version used lock anti phase. If I remember right they have gone from a high side switcher to locked anti phase to the current low side switching.
The manual states the pulse as .9 to 2 ms is this a typo? Should it be 1 to 2 ms and will use the victor motor routines for programming?
Our team has a problem of marathon diver practice . A battery change is not a cool down period. If we end up using Talons they will have fans.
Another motor controller option. I like options. Thanks for the attempt to support First. Have they given any hint of the Talons legality for 2013?

Re: Victor 888: Upgrade to the Victor 884
 

[quote=Gdeaver;1187367]The window motor thermal shut down with the locking pins removed and a jag was only seen when used in a positioning application controlled by a PID. We used the window motors for our swerve steering - 4 wheel independent continuous rotation. With the jag we had intermittent thermal shut down with the jag. We switched to victors and had no more problems even with extended run times during practices in a hot building in the summer. We have used the window motors in other non - positional applications and not had problems with the jags. Of course if the window motor is over loaded it will shut down with any controller. It will live to run again. For what ever the reason jags and window motor in positional applications is probably not a good idea. We have used the banesbot motor and transmission for 2011 and 2012 avoiding this problem.

The output duty cycle is scaled linearly to the input, no additional math was needed to obtain a linear output.

The FRC version of the Jaguar has always been a high side switching synchronous sign-magnitude switcher. If there are any plots to prove otherwise I would like to see them.



This is not a typo. The Victor routines will work with the Talon. It is always a good idea to calibrate any motor controller however.

This is probably a good idea if you are performing back to back practices at your build facility. However in a competition it may not be necessary. If you notice the Talons thermal plots are on a 10 minute interval with a 30% duty cycle (3 minutes at specified current, 7 minutes off). This is on purpose as most matches have ~10 minute turn around. (start to start) Now keep in mind the matches only last 2 minutes and 15 seconds. So even if your robot slams into a wall at full speed at the beginning of auton and continues to run at full speed for the remainder of the match, you will not damage the Talon. With that said it can only help with performance to use the fan. Our rule of thumb is use the fan for any Talon on a 40 amp breaker. Of course this is only relevant if the Talon is deemed legal.

Re: Victor 888: Upgrade to the Victor 884
 

Black Jag. See Figure 4-4 on Page 19:

http://www.ti.com/lit/ug/spmu130c/spmu130c.pdf

Re: Victor 888: Upgrade to the Victor 884
 

As a point of clarification, all of the Victors since their creation (1999) have had conformal coating. The 884 has it and so does the 888 (and so did the 883, 885, etc.).

Re: Victor 888: Upgrade to the Victor 884
 

This is just a guess, but are the 888 and Talon related at all?

Re: Victor 888: Upgrade to the Victor 884
 

No. No relation other than the engineers that work on each are brothers.

However, IFI had no input on the Talon and CTRE had no input on the Victor 888.

Re: Victor 888: Upgrade to the Victor 884
 

Is there any particular benefit to using a Talon over a Victor or Jaguar? Am I correct in thinking it goes something like this:

Jaguar - Cheapest, bulkiest, most flexible functionality

Victor - Most expensive, smallest, most reliable

Talon - Somewhere in-between?

Re: Victor 888: Upgrade to the Victor 884
 

I believe the Talon is smaller then the victor, especially when it is run fan-less. Also the Talon is rated to handle more amps then the victor so victor vs talon reliability is up for question, no one has really tested the Talons like the victors.

Re: Victor 888: Upgrade to the Victor 884
 

Again, for a point of clarity the Victor is $89 so it is not the most expensive. Actually, it is the least expensive compared to the Talon on AM and the Jaguar on Mouser.

Re: Victor 888: Upgrade to the Victor 884
 

It looks like Vex's site is a bit misleading then.

http://www.vexrobotics.com/victor-speed-controller.html

It says "starting at $199.95" but then further down the page it lists "$89.99" as the actual starting price. Possibly because the $90 variant is out of stock. When I checked the first time I only noticed the "starting at" price.

Thanks for the correction.

Re: Victor 888: Upgrade to the Victor 884
 

This is interesting.
I never saw Mike talk about it at all when I saw the Talon, but this alone would make me choose this over the current 884s, even with the price difference. What about the 888's?
We've had instances with failed Jags before and never went back to them, other than a few robot functions for "smoother" output. The Victors size and reliabilty are so much better, other than the occasional poor connection with the PWM input.

Re: Victor 888: Upgrade to the Victor 884
 

It's my understanding that the only difference between a 884 and a 888 is that the out put has been made linear. If you have gown to love the Victors the 888 is the same only one little issue has been fixed. Interesting that this year we lost 2 884's however these were very old units that had been abused on many other robots and a ball lift jam finally killed them. The victors have proven reliable.

Re: Victor 888: Upgrade to the Victor 884
 

As another alternative, I would like to see these used. They are definitely a cheaper alternative:
http://www.canakit.com/50a-dc-pwm-mo...ontroller.html
Especially if you buy in bulk here (10+):
https://www.sparkfun.com/products/9668?

Also, to whom mentioned a lower amp version, they sell a 30A that is just slightly more that 1/2 the price:
http://www.canakit.com/30a-motor-spe...oller-pwm.html

Re: Victor 888: Upgrade to the Victor 884
 

Since those don't accept a servo style PWM input, what would you use them for in a FIRST robot?

Re: Victor 888: Upgrade to the Victor 884
 

Those only control speed, not direction. They also have an inappropriately high minimum voltage, and include knobs. I'll stick with the existing options.