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/vexpro/victor-speed-controller.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.

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

Hmmm, wonder if there is a connection there?

A family connection :slight_smile:

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.

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.

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.

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.

Does it also work with CAN?

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

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?

This version of the Talon does not support CAN.

http://www.chiefdelphi.com/forums/showthread.php?t=83973

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.

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.

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.

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?

[quote=“Gdeaver,post:16,topic:122838”]
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.[/quote]

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

*







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.).

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