Motor Controllers
 

So this is a question that I have had for a few years now, and never really gotten a good answer to it:

Which motor controller is the best for which situation? Meaning is there specific applications were one controller is better then the other, or is there just one motor controller which is the best, period?

This question has resurfaced for me especially with the creation of the new motor controllers such as the spark.

Thanks,
JP
Co-Captain Team 806

Re: Motor Controllers
 

In 2013 we liked the Talon because chips and aluminum dust kept destroying our Jags. We also like the 888 because the fan is already installed.
Going forward we are trying out the new Talons with a CAN bus.

Would like to here from others on how they connect the Talon green and yellow CAN wires together. Vex sells a nice device but it's expensive and it takes up a lot of room.

Dave

Re: Motor Controllers
 

My personal favorite is the Victor 888, but I chose the Spark because it does basically the same thing, costs about half, and it's still available. I would say the only case where I wouldn't use the Spark or Victor is if I wanted to do built-in PID control, where I would use the Talon SRX.

I've used Jaguars a number of times (against my will) and all I can say is NEVER AGAIN. They take up a ton of room, are prone to breaking (I had one that screeched at me), using CAN is practically impossible, and therefore it doesn't do much more than the Victor 888 or Spark.


Can you not just crimp or solder them (cue debate on crimping vs soldering)?

Re: Motor Controllers
 

Ya my team also despises Jaguars

Re: Motor Controllers
 

At this point, I'd still have to consider the Talon SR my favorite, based on the number of motors and hours we have utilized them with zero mishaps. Spike relays would be second for the same reason (no mishaps, fewer hours, though you may not consider them a controller).

It didn't take much use of the Talon SR to send the Jaguars and Victors (a few each 884s and 888s) into our "unused parts" collection.

Being a bit of a "never buy serial number 1 of anything" guy, I have high hopes for most of the various controllers on this list, but none of them has become a favorite yet. I really like the features of the Talon SRX; if it proves to be robust it will probably top my list next year. The Victor SP, Spark, and SD 540 are all in a runoff to displace the obsolescent Talon SR, with cost, reliability, and limit switch capability as ranking factors to be determined. The Jaguar is my least favorite ever controller since becoming associated with FRC in 2012, squarely behind both the Victor 884s and 888s. Every one that the team ever owned has died a painful, stinky death. As much as we wanted to stop using them, we couldn't stop using these fast enough to get any of them out of use before it went up in smoke.

For the record: no vote cast, because my only solid decision among the controllers listed is not jaguar.
Edit:
Ditto Talon SR.

Re: Motor Controllers
 

Wondering why Victor 884/888 was left out of voting yet Jaguar was included?

--Michael Blake

Re: Motor Controllers
 

These JST-SM style connectors are a royal pain to crimp BUT are simply amazing for connecting the talons together:



They are locking. They are cheap. And they are small. Simply awesome.

Crimping guide here explains how to crimp them (and APPs as well): https://www.ebikes.ca/documents/GrinConnectorGuide.pdf

They are just small enough that they are a royal pain to crimp though.

EDIT: We got ours from here because I know someone will ask: http://www.aliexpress.com/item/Free-...352919222.html

Re: Motor Controllers
 

Let's look at this logically:
-There's no reason for a Jaguar to be anyone's favorite
-Some people have chosen the Jaguar as their favorite

Therefore, there is there must be some fraction of people who are answering randomly. We'll assume that the people who choose randomly choose each option with equal probability.

-At this time we see 4/22 people have chosen "Jaguar" as their favorite.
-There are 5 different choices for the poll

Therefore 4/22*5 should give us the fraction of people who are choosing randomly. This comes out to approximately 90%.

QED :D

Re: Motor Controllers
 

We used the 2-position "0.100" Latching Polarizing Connectors" from Hansen Hobbies for the CAN wires on the Talon SRX's last year and had zero problems throughout the competition season plus the 3 or 4 off-season events. The pins can be crimped with the same crimper used for the normal PWM cables. We also crimped Anderson connectors onto the input and output wires so that the whole motor controller can be swapped out quickly and easily (did not have to) or it can be re-used as is. Just be sure to do a pull-test immediately after each and every crimp and to have someone else inspect the work (and repeat the pull-test) to ensure it was all done correctly. We coiled up the excess wire and tied it up neatly using small cable ties. The connectors for the CAN connections were contained within the loop, guaranteeing that no physical strain is put on the connection.

http://hansenhobbies.com/products/co...nlpconnectors/
http://hansenhobbies.com/products/co.../pt1in_lp_1x2/

Re: Motor Controllers
 

Even before I saw the last paragraph about bending the hook, I knew the instructions for removing the pin were wrong. You shouldn't pry the pin up. You just need to push down the spring (referred to in the document as the "ledge") in order to release the pin and let it be pulled out. This is true for the small Anderson connectors and for the large SB50 battery connectors.

Re: Motor Controllers
 

Would agree with that but not my guide... I do think someone needs to create a similar guide for FRC's common connectors though.

Re: Motor Controllers
 

I wonder if the 2016 FRC rules will consider this a "FABRICATED ITEM" and disallow it's use, if it was terminated before kickoff?

So many fun things to consider....

Re: Motor Controllers
 

The 2015 rules has a specific exception for wiring terminations to COTs devices. I would think the 2016 rules would have the same exception. We will see. As a robot inspector, this is not an area I would focus on unless told to anyway.

Re: Motor Controllers
 

It is always a risk when "future proofing" something. What you may have done one year may not be legal the next. At the very least, one can use these motor controllers on a practice robot with very little effort.

Re: Motor Controllers
 

It would have been allowed last year under R12c.
However, this exception was not included for the withholding allowance; if you wanted a pre-terminated controller as a spare part, it needed to be included in the withholding allowance.

Re: Motor Controllers
 

Talon SRX are my favorite. Unless you need the advanced features of the Talon the Victor SP makes more economic sense. I will wait to pass judgement on the new 2016 controllers when they prove their durability.

Other than size the jaguars don't deserve their bad reputation. We found them reliable when connected correct and not filled with metal shavings. :]

Re: Motor Controllers
 

Getting back on topic to answer OP's questions...

As with most things in engineering design, the answer here is "it depends". In my mind there are three key features to look at: cost, capability and reliability. I am only going to focus on the controllers you can buy going forward (Talon SRX, Victor SP, REV Spark, MS SD540). Since you can't get spares for other controllers easily I would stay away from or use them sparingly (and with LOTS of spares ready just in case).

Talon SRX at $90 is the most capable, but also the most expensive.

Capability: Talon SRX allow use of a Controller Area Network (CAN) bus. The other option is Pulse Width Modulation (PWM). With a bus you get two way communication between controllers and the RoboRio.

Also, the Talon SRX has an input data port that allows you to do some routine control calculations directly on the controller instead of using the RoboRio. You can hookup small breakout boards to the data port and do a number of control loops. Some examples are that you can hookup an encoder to a shaft and thru the data port and tell the motor controller to drive forward until the encoder has reached 1000 ticks and then stop. Another example is that you can tell the motor controller to drive forward until the upper limit switch on your elevator is tripped and then stop. With PWM the RoboRio has to check all these sensors and issue the commands to stop. Since the RoboRio is doing a lot of calculations it may be slower to respond (by some number of milliseconds) to when the switch is tripped on your elevator. The Talon SRX offloads these mundane control calculations from the RoboRio.

Cost: You pay for all these nice features (CAN bus chip, extra connector for data port inputs). Over a whole bot this extra cost can add up.

Reliability: Last season the Talon SRX performed well with few (if any) failures. Since there was no defense and therefore few long duration high current pushing matches, there could be an argument made that some more testing is needed under these extreme conditions. Most people would agree it is a solid and FRC tested design. It also has a very small foot print and a sealed aluminum enclosure. This prevents debris from getting in and shorting out electrical components (a problem with older controllers). Aluminum is a great heat conductor and allows the heat generated by the controller to be moved away from the electronic chips without the need for a separate fan.



Victor SP at $60 is a robust, but basic controller.

Capability: Talon SP is a simple Pulse Width Modulation (PWM) driven controller. No fancy data inputs, just the ability to set the speed between 0 and 100%.

Cost: You pay for a smaller form factor and an aluminum case. More expensive than other PWM controllers and does not have data inputs.

Reliability: Same as Talon SRX. Most would agree it is a proven, dependable controller for FRC.


REV Spark at $45 is a new low cost controller with some nice looking features.

Capability: REV Spark is a simple Pulse Width Modulation (PWM) driven controller. You can set the speed between 0 and 100%. It also has a basic input data port that will allow you to directly wire in a set of limit switches to stop it. These limit switches are great for an elevator or a rotary arm with a top/bottom limit switch. No fancy encoder or other control capabilities. Pretty impressive for such a low cost device.

Cost: Cheapest one on the market for FRC right now.

Reliability: This is brand new this year. Preliminary test data looks positive. It has a plastic case, which will not transfer heat as well as aluminum. It claims not to need fan cooling, which is being tested in lab conditions (I believe results release soon). Obviously the real test is to see it during the season. Be cautious about switching to a new controller with limited testing unless you can afford to replace the controllers. It is a bit larger than the Victor SP and Talon SRX. For the price it looks promising.


MS SD540 at $50 is a new low cost controller with some nice looking features.

The SD540 implements many of the same features that the REV Spark does, albeit in a different layout. There are some concerns about the design choices made for the SD540 that are detailed in another thread. Same overall story - low cost plastic body controller with PWM input and limit switch control build in. Untested.



Hope that helps. PM me for more detail (I glossed some of the nitty gritty details)

-matto-

Re: Motor Controllers
 

I wonder why they made that distinction. Is it too much of an advantage to have a drop-in replacement motor or controller ready to go?

I could see the first task for a student in the pit being to crimp some connectors onto a set of spare motors and controllers, ready to go.

In fact... *writes that down*

As for the poll, I voted for Talon SRX since it seems to offer quite a lot of potential advantages for the fairly minimal extra cost. Virtually every one of our robot failures last year, both on our practice field and unfortunately during our first regional, was some combination of our software addressing the incorrect PWM or DIO, the encoder wired incorrectly, read incorrectly, software values set/reset incorrectly, motors trying to run the forklift past the edge (e.g. we didn't have time to wire in a hard limit switch), etc. If we thought to use the limit switch and encoder functionality in the Talon SRX, and communicate over CAN instead of PWMs and DIOs, our code (and failure modes) could have been much simpler.

Re: Motor Controllers
 

simply because this is all of the current motor controllers, nothing as far as I know has been made to replace the jaguar.

Re: Motor Controllers
 

Though they don't have the same name (because they're made by different companies IIRC) the Talon SRX effectively replaces the Jaguar. It does the same PID control, limit switches, etc with better CAN support. I wouldn't buy Jaguars new even if they still were for sale.

Re: Motor Controllers
 

:( Jaguar is my least favorite, but I couldn't let that challenge pass. I came up with three reasons for Jag to be someone's favorite (I left out nostalgia and thinks like being the biggest, heaviest, and having the smallest continuous current capability, and having a nonstandard PWM response):

• Supply Voltage: works down to 5.5V and up to 30V, Tied for first best at both ends with SPARK.
• Aesthetics: The jaguar case is a work of art compared to the boxes with fans (Victor 884 and 888) and the boxes without fans (the others).
• You can control a Jaguar with RS-232. I can contrive of a few applications where this would be useful, like controlling from an old PC.

Edit:
Now I feel cheated; I've smelled and seen plenty of blue smoke, but never seen flames:( ;) .

Re: Motor Controllers
 

PWM from parallel port and they all can be controlled by an old PC ;)

I am waiting for the single IC speed control module. It is coming. Just a chip with bolts on the top like an IGBT and an electrically isolated metal plate on the bottom.

Re: Motor Controllers
 

I'd never heard of this, and a bit of web searches about the old centronics port leads me to think that the PC-side hardware was not made to support PWM; whether it would be possible to hack it with a tight loop that shut down the PC for any other purposes is probably hardware dependent. Has someone actually done this (using passive components, which was my meaning)?

Heat dissipation is a big issue here, unless you're talking about replacing the spike rather than a speed controller. The amount of electrical isolation demanded by FIRST is also a steep challenge. I expect brush-less motors and controllers to be FRC legal before single-chip brushed motor speed controllers. I'm not holding my breath on either one.

Re: Motor Controllers
 

Don't forget the fact that the flames that poured out of Jags were very entertaining for the kids!

Re: Motor Controllers
 

Ether did PWM 'bit banging' of the handshake wires on a serial port:

http://www.chiefdelphi.com/forums/sh...52&postcount=1

I used to play .mod MIDI files on a parallel port justing just a resistor ladder and a capacitor to couple still have that stuff somewhere and that was on a Intel 80386 DX 16MHz. That's complex analog audio at up to 15kHz. So yes I am sure if I sat there with some C code I could control several FRC PWM speed control on FreeDOS. I would not attempt this in on any Windows NT kernel because you need a kernel mode driver. It is likely possible on BSD/Linux.

DOS runs in real mode. You will not block the timer interrupts or other interrupts doing this. I used to run this silly trick even with EMM386 running and Windows 3.11.

HighTreason take it away old school...
https://youtu.be/4KUdBgg8Oe4

Then again....I still maintain Commodore 64 code I wrote....so I am pretty dusty.

The heat dissipation of any single part in an FRC robot is no where near the heat dissipation of the big IGBT we used to charge Navy submarine batteries with this big charger we built. The base of the integrated package is metal and you torque the package to the heatsink plate with either a coupling patch or compound. One of my cohorts left a databook on a board during a test...let's just say we will not read that databook again ;).

The issue is merely distributing the heat away from the parts that get hot. Either make them more efficient or make the removal of heat more efficient. Same reason we could fill power supplies up with canola oil....as long as you do not let the pressure build or reach the flash point it will not conduct but it will make the heat distribute around (do not try at home kids). That silly trick allowed almost double the wattage from a power supply. By the way - TDI in Hackettstown, NJ was selling a design like this actively before AstroDyne bought them.

There was a time when people argued no FRC speed control would last without a fan either. Power MOSFETs keep getting better and better. Lower the switching losses and on state resistance enough and the heat dissipation will follow. Just please do not do it with silver in the semiconductor die (let's just say it makes the power semiconductors go bad eventually and leave it there).

Re: Motor Controllers
 

I'll accept your word and Ether's.

I think you made my point better than I did.

Re: Motor Controllers
 

The actual problem is not actually the heat:
It is the whether doing that tight integration is financially workable given the market.

A massive power transistor has a much wider market than FRC and a much higher price point.

However with all the interest in drones and places like SuperDroidRobotics selling kits that are FRC size like for plows and snowblowers...the market is growing.

I suspect back in the day when audio receivers were individual power transistors many people also thought they would not be surpassed by integrated modules. Odds are if you tear down a retail home reciever you find modules in plenty of them.

Re: Motor Controllers
 

Well the new Talon SRX is best if you can take advantage of what it offers over the Victor SP which is control by CAN and direct sensor feedback (encoders). This is why it costs more. If you can't take advantage of that then the Victor SP is better because it is cheaper and offers the same size advantages as the SRX. Hope that helps.

Also, Jag - ewww - don't use that...

Re: Motor Controllers
 

Part of my own evaluation of the SPARK was having a look inside. While much of the case is plastic, the SPARK label in the center is covering a heavy c-channel shaped slug of aluminum with heat transfer pads to encourage cooling of the 4 MOSFETs and 3 electrolytic capacitors under it. My gut feel (with nothing but experience to back it up) tells me this device will survive a 2-minute pushing match just fine.

The footprint is close, but not identical to that of the Talon SR.

Re: Motor Controllers
 

Check these out.
We used these last season. They're toolless, and we've never had a problem with them falling off or breaking. They're designed for larger wires than the CAN wires, but they still work fine. They're a little bulky, but not big enough to cause problems.

Re: Motor Controllers
 

I don't have one to look at, but what I said is still true based on what you are describing. The internal aluminum heatsink will draw heat away from the components, which is helpful, but you need to look at the path the heat takes after that. In the case of the REV spark, this means conduction through a plastic case of some thickness then out to whatever the controller is mounted to. Compared with the aluminum body of the Victor/Talon that does not have this additional layer of restriction. Keep in mind that plastics have Thermal Conductivity of <1 W/mK compared with Aluminum that has Thermal Conductivity of 200 W/mK. While it is true the footprint sizes are different, my guess is that this will not have a large effect, especially if there is no thermal paste/pad between the aluminum heatsink and the plastic case.

For effective thermal management I like mounting the controllers to a hefty aluminum frame member or sheet metal belly pan of decent thickness. Wood or plastic or heavily pocketed aluminum belly pans limit the ability to conduct heat away from the mounting location.

Perhaps the REV will be fine for most situations, but what I said is still true - the Victor/Talon will be better because there is no plastic in the thermal conduction path. I believe REV is planning to release test data soon. Hopefully they will instrument down to the package level or heatsink right next to the MOSFET case and will provide ThetaJC values for the devices. The junction temperature is what is key for long term performance and reliability.

It really depends on current draw of the motors and efficiency of the controllers during matches as to how much heat you really need to dump. But keep in mind that in a Best-of-3 Finals match that you do not have as much time to cool off as during a normal match. It can be a problem.

TL DR: REV may be fine, but Victor/Talon will be better for dumping heat.

-matto-

Re: Motor Controllers
 

I'm not questioning any thing you've said, and I fully understand that the slug of aluminum only buys time, and in the end the vast majority of heat must be radiated to the environment through the 1.5-ish square inches of aluminum exposed to the air.

Having spent some time within the Talon SR and the Spark, it is my opinion that teams familiar with the Talon SR will see similar results from the Spark.