SD540 Motor Controller
 

The SD540 Motor Controller is now shipping! A seemingly weightless, low cost solution with great functionality is now here and ready to order.

We had great feedback at the recent FRC workshop in Richmond, VA. Many local teams got a chance to experience using the SD540 Motor Controller first hand and witness its amazing control.

Product page

Specs

Performance Testing

Re: SD540 Motor Controller
 

Do you have a CAD model of the controllers? I looked around the website but didn't find them, I'd like to add them to our CAD library.

Why are the dip switches on the bottom of the unit, seems like it would make it difficult to adjust once they are on the robot.

Re: SD540 Motor Controller
 

Go to the product page, and click on the download tab on the left hand side of the page.

Re: SD540 Motor Controller
 

My 2 seem fine, thanks!

Re: SD540 Motor Controller
 

Thanks, I thought I looked there but I guess I missed it.

SD540 Motor Controller Comparison
 

See how the SD540 Motor Controller compares with the other FRC controllers available:


The majority of the information on this chart has been taken from the comparison chart form REV Robotics.
See their chart here:
http://www.revrobotics.com/wp-conten...6132225162.jpg

Similar charts can also be found in Talon SRX, Victor SP, Victor 888, Talon SR, and Jaguar documentation.

Re: SD540 Motor Controller
 

Quick question, does having a higher output frequency cause any sort of performance difference?

Re: SD540 Motor Controller Comparison
 

Not to be a buzz kill but did you guys just copy the data complied by REV for the Spark? Even the disclaimer is the same.

Re: SD540 Motor Controller Comparison
 

I would compare this to the Spark or Victor SP. In terms of weight it beats both, is only $5 more expensive than the Spark, has a limit switch input, and has a thinner form factor than the Spark (although not as flat as the others). The output frequency is also higher, although I'm not sure what effect that has.
The banking option looks handy to slightly lower the cost and use less mounting hardware.
Looks pretty neat, overall! We would buy them if not for the twenty Talons we already own. :P

Re: SD540 Motor Controller
 

Higher switching frequency will make thing more efficient, and power delivery will be continues rather than discrete. In other words better linearity and smooth operation.

Re: SD540 Motor Controller
 

What does "multi-bank" mean? I see nothing on the web pages that gives me even a hint of a clue. The price sounds pretty good, but perhaps if I understood what "multi-bank" means it would actually be worth buying.

Re: SD540 Motor Controller
 

I'd like to know how the upgradable firmware works. Can you shed any light on that?

Re: SD540 Motor Controller
 

Packaged as single, dual, or quad
Examples:
http://www.mindsensors.com/frc/139-m...-frc-bank-of-4
http://www.mindsensors.com/frc/138-m...-frc-bank-of-2

Re: SD540 Motor Controller
 

If you scroll down the the bottom of the webpage, you'll see there's a "pod" of 4 motor controllers referred to as the "Quad-Bank Model" and a subsequent Dual Bank Model. It's essentially a block of motor controllers.

Re: SD540 Motor Controller
 

At the workshop they said you could replace one of the controllers on the bank without having to replace the entire bank. Not entirely sure how that works in relation with the rules though.

Re: SD540 Motor Controller
 

For the 7 people who say they "do not like this product" could I ask why? Seems like a perfectly competitive option. What is there to not like?

Re: SD540 Motor Controller
 

Have you tested the higher switching frequency for interactions with the locking pins in the window motors?

Re: SD540 Motor Controller
 

It could be that it's new. It might also be kids who have no idea what they are talking about. I really think it's the fact that some folks just like to be snarky when a poll is anonymous.

Re: SD540 Motor Controller
 

I like both the sd540 and spark for the same reason-cost. The Spark currently wins this albeit only slightly. The size difference isn't enough for me to really care and the low weight scares me for use with higher power motors (whether that fear is justified has yet to be seen-if it doesn't matter then it's definitely a nice boon).

Of those two my favorite is the one that's more reliable, available and has better customer support.

Re: SD540 Motor Controller
 

There's also no "I'm ambivalent about these features" option. "I do not like it, Sam-I-Am" becomes the default option, since the others are super positive about the product.

From my chair, none of the features of the SD540 stand above my primary criteria for selection of a speed-controller, which is "Reliable, as verified by real FRC teams using real hardware on a real robot".

Not to imply that the product isn't reliable, just that being burned to the tune of a set of speed controllers during build/competition season is enough disincentive to keep me preferring more tried-and-true offerings.

Re: SD540 Motor Controller
 

I like the idea that the output has a higher signal frequency. Plus if it is more efficient at transferring power, it won't get as hot. Time will tell if these differences are significant.

Big plus in either case is now we have smaller, lighter and more chip resistant motor controllers! This is a big change from just a few years ago.

Dave

Re: SD540 Motor Controller
 

I haven't seen anything that states whether or not it is FRC legal for 2016. If it isn't, then why are we wasting time on it?

Re: SD540 Motor Controller
 

http://www.chiefdelphi.com/forums/sh...88&postcount=1

Cough cough.

Re: SD540 Motor Controller
 

http://archive.usfirst.org/roboticsp...or-controllers

So yeah, it's legal.

Re: SD540 Motor Controller
 

Since this controller is currently only a PWM device, we will release a device to perform the firmware upgrade. All you have to do is connect it and change it to bootloader mode with the dip switches. More information will be available once the device it released.

Re: SD540 Motor Controller Comparison
 

Credit has now been given below the chart.

Re: SD540 Motor Controller
 

What motor rating are you worried about?

Re: SD540 Motor Controller
 

Emphasis added... are there plans to enable other communication methods line CAN? Possibilities or plans to interface this with encoders in the future?

Re: SD540 Motor Controller
 

I think you'll find the rating most teams will care about is, "has been run by many other teams on many different robots without failure".

for 90% of FRC teams, all the other specs are meaningless. They just want something to make the motor spin without failure.

Re: SD540 Motor Controller
 

I was just worried about overheating problems in heavy duty applications like drivetrain. At around 60% the weight of other controllers there is substantially less thermal mass. I'm worried about it but it may be a non issue (especially if it's more efficient). I'll wait for teams to use them before I make final judgement.

Within reason, cost and reliability > all other factors for a speed controller IMHO.

Re: SD540 Motor Controller
 

We are planning on implementing CAN on future models. Possibly as a single board swap out kit. The firmware upgrader will actually use I2C that is already implemented for bootloading the device.

Re: SD540 Motor Controller
 

Have you seen the results of our performance tests? Check it out at the link below.

http://www.mindsensors.com/content/7...haracteristics

Re: SD540 Motor Controller
 

It seems to be getting quite hot; I'm not sure I would consider these for my drivetrain.

Re: SD540 Motor Controller
 

This graph doesn't mean anything to most teams.

They need to see it run by a bunch of teams in a bunch of different applications w/o failure before they believe in it.

Re: SD540 Motor Controller
 

Those results show a 50 amp load with the motor mechanically stalled. Even then, after two minutes the controller is under 100 degrees Celsius.

If you typically stall your motors for 5 minutes at 50 amps, then temperature might be of concern.

Re: SD540 Motor Controller
 

The stalling doesn't matter as much as the current; IIRC the heat generated is proportional to current.
I would be worried about getting a burn or burning something at that temperature. Plus, CIMs often run at high currents for the duration of the match; it's certainly possible to average 40-50 amps for a match.

Re: SD540 Motor Controller
 

There's definitely inertia in teams adopting any new item, whether part of the control system, an actuator, or a mechanical system. Our overwhelmingly positive experiences with the Talon SR and Spike (and negative experiences with Victors and even worse with Jaguars) led us to use these two motor controllers/switches exclusively last year. This year, especially as the Talon SR has been discontinued, we do plan some experimentation with the Talon SRX, and some of the new less expensive motor controllers (SPARK and SD540). Over the years as an occasional purchaser for the government, I've learned to take vendors' tests with a big grain of salt. It's rather harsh to say this, but one failure under conditions where we cannot produce calculations that would lead us to expect failure or which may be beyond our reasonable control can put a motor controller on our black list, along with the Jags and Victors. At this point, we keep Vics and Jags around just to give the freshmen a sense of how much things have improved even in recent years; we haven't put either on so much as an off-season project in over two years.

In the interest of total disclosure, I am personally quite harsh on vendors who seriously disappoint me. For example, I haven't had a McDonalds hamburger since my sophomore year in high school (can't you dress a hamburger without including that awful special sauce?), and I haven't bought anything but a few batteries and tires (and those under otherwise desperate situations) from Wal-Mart in over ten years. The traffic from selling groceries drove me 90+% away circa 2003; the way they abandoned New Orleans after Katrina in contradiction of all of their advertising about helping communities after disasters sealed the deal.

This is competing with the spark but, the spark has the advantage of being from a more experienced company, and looking pretty. It looks decent and we will buy one to test but for us staying with talon SRX'es and Sparks or Victor Sp's for this year make sense.

Next year we will see how people feel about these guys and it they work we will use them.

Re: SD540 Motor Controller
 

Honestly I don't have many feelings one way or another about this speed controller (our team uses CAN).
That said, a few things did stick out for me...

• It requires me to have 6-32 screws, and have them at a specific length to mount to anything (Imo, through holes are better, and allow you to avoid hunting for "that one screw").
• The signal input connector seems like an odd choice, and it looks like the kind of thing that PWM cables could fall out of easily, and then, due to lack of labeling, get reconnected incorrectly.
• If you have a bank of controllers, and one of them dies, do you have to replace the whole bank?
• Would be nice if brake/coast could be changed on the fly (we used to do this with victors by connecting a PWM cable where the jumper would go).

Might get one of these to play around with it, but generally we avoid new, un-FRC-proven components the first year they're out (unless there are no alternatives like in 2014).

Re: SD540 Motor Controller
 

To answer your questions:
The mounting screws are included when you purchase the SD540. Also, our case is 3D printed so there are multiple options in the works that do not call for a complete redesign. We plan to release casing options with different mounting options and through holes.

The connector is not only for PWM. Currently it allows for firmware updates, and in the future CAN, encoder connection, and possible I2C. Labels are on the bottom.

If a unit dies on one of the multi-bank options, you only need to replace that unit. A kit will be offered for just such a situation.

Brake/coast can be changed on the fly. There is a dip switch on the bottom that just needs to be flipped. You can also change direction.

Re: SD540 Motor Controller
 

oops. double post.

Re: SD540 Motor Controller
 

It would be best if Mindsensors can present time/temperature charts that show the temperature stabilizing. It would be even better if you can present such charts with different (continuous) loads (10%, 20%, 40%, 60%, 80%, 100%). In FRC, it is rare that a motor controller would be run for the duration of the match at the same current level but these extra load lines can give the users some indication of what kinds of temperatures they can expect by estimating their average current over a short time period. The time/temperature charts will also give some indication of what the short term thermal capacity of the motor controller is; i.e. it may withstand an 80A load for 1 second better than it can withstand a 50A load for 2 minutes or longer). Your chart ends at just past 4 1/2 minutes which is much longer than a standard FRC match. In practice sessions, we have often run our robots continuously for much longer than 4 1/2 minutes, often repeating the most stressful actions. Considering how quickly the temperature is still rising at 270 seconds, I would be concerned that the transistors hit thermal-runaway and self destruct.

It is also of concern to me that your time/temperature chart is reaching almost 100 degrees at 150 seconds and about 125 degrees at 270 seconds, with your initial temperature of 25 degrees. It appears from your photo that these temperatures are measured on the top of the heatsink. If this is true, your transistor junction temperatures (taking into account the thermal impedance through the base plate of the your heatsink and the junction-to-case thermal impedance) will be much higher, possibly leaving you with very little (or no) margin from the maximum operating temperature of your transistors, depending on your device type. These high junction temperatures will lead to reduced life of the transistors. Have you done extended life testing on your motor controllers? Batch-to-batch variations in the transistor characteristics can have a large effect on your temperature performance so a test result showing little or no thermal margin raises red flags in my mind.

Lastly, the high heatsink temperatures are a concern, as Asid has also pointed out. Various safety standards specify different "maximum touch temperatures" but they will all be well below 100 degrees C (UL/IEC 60950-1 specifies a maximum of 75 C). With the thermal mass of your heatsink, temperatures at 100 degrees and above will most likely cause serious burns to anyone touching the heatsink. America has far too many lawyers. Some of them have children on FRC teams. I would not want to see Mindsensors dragged into court and many students be deprived of a great resource.

I am sorry if I am being hard on Mindsensors. They have a pretty good history in educational and hobby robotics where the power levels are low (NXT/EV3, Raspberry Pi, Arduino) and the energy sources have limited capacity (AA's or equivalent). They have now entered an arena where the energy levels are much higher and the hazards and consequences are much more serious. My comments and warnings are based on my experience developing power electronics products for mass production over the last 20+ years.


The heat generated has two components; the switching loss in the output transistors and the conduction loss of the output transistors. The switching loss is roughly proportional to the switching frequency (output frequency) of the controller. The conduction loss is calculated by multiplying the on-resistance of the output MOSFET (at the instantaneous operating current) with the square of the instantaneous output current (P = R x I^2).

I have not seen actual efficiency numbers for any of the motor controllers currently in use or for the new ones from Rev and Mindsensors so it is not clear how people in this thread are saying that the new controllers are more efficient.

Re: SD540 Motor Controller
 

Is there a polarizing feature on this connector? Connectors of this type, with 16 pins generally don't fall out on their own but changing to one with latches would give added security.

How many mating cycles is the connector rated for? It looks like a tin plated type in the photo. One major manufacturer of such connectors, Tyco Electronics, considers 50 cycles a "large number" for their tin plated connectors. This means they will not guarantee "stable electrical contact" after 50 mating cycles.

http://www.te.com/documentation/whit...f/sncomrep.pdf

Re: SD540 Motor Controller
 

This product looks like something that was developed by someone with limited FRC experience. The features being touted as benefits are actually detractors in my mind:

- Lightweight (The difference is negligible in my mind. If we get to the point where we need to save a fraction of a pound, we get out the big drill or hole saw. I also question what was skimped to get the weight loss.)
- Low Cost (REV Spark is $5 cheaper and has fewer issues that I can see. Honestly this controller would have to be under $40 for me to consider buying over the REV.)
- Multi Bank Option (Sure we need a bank of controllers for the drive train, but sometimes they need to be placed creatively to get the rest of the bot to work. I can mount them touching each other just fine by myself without the need for the bank. Also there is no air gap between controllers. I like a small air gap, especially if these are the drive train motors that will producing a good deal of heat.)

Things I like:

1) Well labeled (colored) inputs and outputs

2) Robust screw terminals for a ring type connector or bare wire

Things I dislike:

1) Single 16 pin male connector with no cable retention. It is very easy to plug the PWM into the limit switch pins or vice versa. Do I use a standard PWM connector (3x1) and two 2 pin limit switches connectors? Or do I make my own 16 pin custom connectors? How do these stay in during the season (please no more hot glue)? How do I keep the exposed male pins safe (especially from student hands when they are rooting around in the belly pan)? Also I am not sure why connectors are mounted parallel to the mounting face instead on normal to it (this will increase the part footprint quite a bit when it is used).

2) Brake/Coast & Cal under the mounting face. To me this is inexcusable. If I want to change/control the mode or re-cal a controller I have to demount these (by unscrewing them from the bottom - see #3)?! Why not use the spare 8 pins on the connector for these features?

3) Lack of thru hole mounting. I can't zip tie these down to something temporarily. Grrrrr.

4) Heatsinking. The test data shows a test at 50A continuous and does not reach steady state in the data provided. Not sure why you used 50A and not 60A (since the specs say 60A continuous). We want a controller we can practice with for long sessions, not just one FRC match. Based on your test data it looks like you will hit a steady state temp of 140-150C on the heatsink, curious what junction temp you will hit on active devices. If you are relying on a thermal pad or thermal grease to keep your ICs cool, what happens over a period of time as these degrade? We want to keep these controllers for a few years! Your test needs to be repeated many times at different loading profiles to convince me you have a proper passive thermal cooling design (and at 60A continuous like the spec sheet says). If you can truly run the controller at 60A continuous (and are not just copying the IC's specs) then show multiple 15-20 minute tests of a single controller at 60A.

5) 3D printed case. Other plastic manufacturing methods would make more consistent parts for cheaper and with better properties (at the right manufacturing quantities).

6) No CAN. I don't expect this in a low cost controller, but would love to have it.

As others have noted, these concerns lead me to believe there will be reliability problems when using this controller during FRC season. It is a great prototype, but needs some major packaging rework.

-matto-

Re: SD540 Motor Controller
 

It would be good if Mindsensors could provide temperature test data covering the 2-bank and 4-bank configurations with all inverters in the bank loaded the same way. Because the individual inverters are right next to each other and the heatsinks rely on convection cooling, the heat coming off one heatsink WILL cause the temperature on the adjacent heat sinks to be higher than if there were "ample space" around individual heatsinks. A simple test of this would be to monitor the heatsink temperature of all 4 heatsinks of a 4-bank controller where only one of the middle ones is loaded and the other 3 are not loaded. The two heatsinks on either side of the loaded inverter will be hotter than ambient.

Temperature test data with the controllers mounted in different orientations would also be helpful to the potential users.


Solid wire would be acceptable under the screw head but no one should be using solid wire on a robot. Stranded wire would be risky since it could slip out. Mindsensors can add a clamp plate under the screw head for just pennies to make this safe with bare, stranded wire.



Locating the 16-pin connector and the Brake/Coast & Cal DIP switch to the top surface would increase the footprint of the product. While they are at it, they may as well move the LED's to the top surface so they would not be obscured by the wiring.


The blind, threaded mounting holes on the bottom may be a very bad idea. What happens when a screw that is too long is screwed in till it bottoms out and is continued to be driven in? Will it damage the circuit board? Will it cause a short circuit and possibly a fire? Will it push the heatsink off the top?

Making it mandatory to have access to the back side of the mounting surface severely restricts where these can be mounted and remain serviceable. The mounting holes will have to be drilled pretty accurately or nothing will line up. The low-resource teams who are likely to be attracted to this controller will likely find it hard to do this. Mounting ears that one can match-drill from the front side would have been much better.


If this product does gain wide acceptance, will Mindsensors be able to manufacture them fast enough? The build period for FRC is very short and not receiving their motor controllers in a timely manner would be (near) fatal for any team.


Mindsensors may want to consider dropping the switching frequency to half of what they are using now. It would cut the switching losses in the transistors in half and should reduce the heatsink temperatures very significantly. It is not clear what benefit the 32kHz switching frequency gives. It may also be beneficial to attach a fan like those used to cool the CPU's in a desktop computer. A modest amount of air flow will increase the heat removal capacity of the heatsink by several times.

As it is, the high heatsink temperatures would make me question the service life of the product. Any electrolytic capacitors used in the controller would live a very short life since they are typically rated for operation in an 85 degrees C environment with some available that are rated for 105 (but they are more expensive and probably physically larger). Mindsensors may also want to check the temperature rating of the plastic they are using for the casing since many are only rated for around 90 degrees C.

Re: SD540 Motor Controller
 

I was more referring to changing the Brake/Coast state while the robot is in operation using a signal input.

Is there actually an associated connector that goes with the speed controller? Just looking at it, it looks like you're expected to just connect the 3-pin PWM and 2-pin limit switch cables directly into the port at their associated pins (like the front panel button/LED pinouts on a PC motherboard).

Re: SD540 Motor Controller
 

The 16-pin connector is normally used with something like the one in the link below.

https://wwws.samtec.com/technical-sp...iesMaster=HCSD


I looked more closely at the drawing showing the pinout of the connector.

http://www.mindsensors.com/content/7...tor-controller

It does look like one would plug a standard 3-pin connector onto 3 of the 16 pins then plug a 2-pin connector onto 2 of the other pins for limit switches. This is a somewhat dangerous way to do it since if the PWM cable is plugged onto the wrong pins, either the motor controller, the robot controller or both may be damaged. Now I know what aldaeron was referring to when he wrote "It is very easy to plug the PWM into the limit switch pins or vice versa."

Re: SD540 Motor Controller
 

I agree. If we get these, we shall also get a bunch of 2x8 housings and clearly label one long edge with red and the other with green (or something similar) to clearly communicate "this side up" to the wiring team. We might even notch it some way and put our own tabs in place to prevent an incorrect insertion.

Re: SD540 Motor Controller
 

You could also get some 1 x 4 and 1 x 5 housings, insert some female pins and plug them onto the unused pins to block them off. This would allow you to use the standard 1 x 3 and 1 x 2 connectors that you are probably already using. Hansen Hobbies has the needed parts.

Re: SD540 Motor Controller
 

Check out this video of the SD540 in action!!

Re: SD540 Motor Controller
 

Now do the same thing on a 2014 style 6 CIM traction 6 wheel drive that belongs to another team so they can independently beat them up.

Re: SD540 Motor Controller
 

Presuming 6 CIMs are legal in the drive train this year :rolleyes:

::ducks and covers::

Re: SD540 Motor Controller
 

I want to see it on a 2 (1 per side) CIM pushybot with good traction being abused for 3+ minutes with a temperature measurement at the end. I think that's about as "worst case scenario" you can reasonably get for that speed controller.

Re: SD540 Motor Controller
 

That's my point though, the average team that uses PWMs is not going to go out and buy a bunch of these 16 pin connectors (which also adds to the cost of each controller), strip apart the ribbon cables, and splice each one with a 3-pin and 2 2-pin PWM cables, they're going to just plug a standard PWM cable into it, which seems like a terrible idea with this connector.

What's with that shaking/noise in the bot at the beginning of the video? It goes away at about the 14 second mark, and then comes back again at ~24 seconds.

Re: SD540 Motor Controller
 

I would like to hope any terrible rattling you hear is a mechanical problem with their test bot. Though it wouldn't speak well to their quality of building robots (and therefore robot parts), I don't think it should affect your opinion on the motor controller itself. Although, we did have one Jaguar that squeaked at us......

Re: SD540 Motor Controller
 

The test program switches the direction at full speed every 200ms for a given amount of times, then runs for a few seconds and switches direction at full speed again..

This tests the responsiveness of the controller as well as the peak currents on the floating motors. This test was run for 15 minutes without failure.

Re: SD540 Motor Controller
 

Those connectors can be purchased for under $2 each but it would be another part to buy and keep in stock. They take some finesse and knowledge to assemble correctly. It can be pretty easy to short out adjacent wires or get the ribbon cable swapped like the ones for the DIO's a couple of years ago. As the person responsible for teaching the electrical skills on our team, I would not want to have to teach yet another fiddly skill and to have to do QC on it.

Plugging a PWM cable into the 16-pin connector can be dangerous because there is nothing on the case of the controller indicating which pin the Pin 1 of the cable should plug onto. One would have to refer to drawings or manuals which are not always available. It would be best if the cable connection had some sore of key to prevent a reverse connection or at least the product is self-documenting in a way that is clearly visible. The connector being on the side makes it very difficult to use any sort of alignment marks that may be on the enclosure.


There have to be some objective test criteria for any test to be meaningful. What were the heat sink temperatures at the end of the 15 minutes? What were the peak and average currents during this test? Do the currents approach the maximum rated current (or current limit level, if there is such a feature)? What happens if the motors are run at "full power" for 1 or 2 seconds at a time for the full 15 minutes. The momentum of the robot will really come into play making it a more realistic test. How many drivers can switch directions 5 times in one second?

If the temperatures get as high as your published data shows, the service life of some of the parts in your product will drop from years to months or even weeks, most likely leading to failure of the controller. In our practice sessions our drivers will run until the batteries are noticeably weak (typically half an hour, depending on the total number of motors) then they will do a quick swap of the battery (1-2 minutes) and start practicing again. Some of the motors/controllers could be running at full load, essentially continuously, for a couple of hours at a time. I would not doubt that many other teams practice in the same way. Time is precious in this competition. No one can afford to wait for parts to cool down before continuing to practice.

Re: SD540 Motor Controller
 

Can they be purchased without the 3d printed parts in a sort of "Kit"?

Re: SD540 Motor Controller
 

Do you have a particular drive train like that in mind?
If you do I have 2 of these speed controls and a lot of spare parts.
Depending on what you have in mind I may have everything required.

Re: SD540 Motor Controller
 

How many FRC teams have these been beta tested with?

Agreeing with Adam...that's usually what most of us care about.

What is your current inventory like? Supply limitations are usually a big turn-off.

Re: SD540 Motor Controller
 

full FRC weight (154lbs with bumpers and battery) plaction (or similar) wheels at around 10fps. That's about the worse I've seen at a competition. A test both with and without fans would also be interesting if you don't mind.

Re: SD540 Motor Controller
 

That sounds more realistic.

Do you have a way to monitor or measure the temperature of the heatsinks?

Re: SD540 Motor Controller
 

Do you have a protocol for this?

Re: SD540 Motor Controller
 

Does it really matter if it has bumpers if it is the proper weight?

I have 4", 6" and 8" AndyMark plaction wheels: I assume 4"?
I'll likely stick with the keyed shafts as I only have a limited amount of hex shaft and bearings.
What distance between the wheels (frame dimension)?
What configuration of the wheels: center drop with 6 wheels all driven with chain?

Fans are no problem I have fans and a CFM meter somewhere.

I have a lot of ways I can measure and log temperature.
What sort of resolution are you after?

Anyone care if a cRIO is used as the control system for this test?
I'll use the FRC approved master breaker and the FRC PDB that came with the cRIO if I do that.

Re: SD540 Motor Controller
 

He was just saying that 154lbs is the actual max FRC Robot weight. Some people might think they should test at 120lbs since that is the weight limit but they would be forgetting the 34lbs from bumpers and battery.

Re: SD540 Motor Controller
 

I've got plenty of exercise weights I can toss on there.

Re: SD540 Motor Controller
 

Most safety standards state that parts that can be touched (i.e. the heatsink) should remain below 65 to 75 degrees C. With approximately a 25 degree C ambient temperature, those numbers will also leave plenty of thermal margin for most electronic parts such that their lifetime is acceptable (in the range of years).

One would want to see the temperature stabilize for some reasonable period of time. Considering the small thermal mass of the heatsink on this controller, a 2-3 degree range over 5 minutes seems reasonable. It certainly should not still be showing an upward trend as in the data published by Mindsensors. In our lab at work, we stop the tests after there is less than 1 degree C of variation over an hour but that is not realistic here with a robot that is constantly in motion and a load that is not held constant.

Re: SD540 Motor Controller
 

Is there any data on all this floating around somewhere for existing motor controllers? Obviously, we know that the existing victors and talons work fine, but it would be interesting to see the data from the new controllers compared to an existing one rather than seeing numbers thrown out without any intuitive scale.

Re: SD540 Motor Controller
 

Single stage and single CIM AndyMark Stackerbox with a 3.57:1 ratio feeding a 12 tooth double sprocket which is #35 chain driving a 26 tooth sprocket on the AndyMark 4" plaction tires. Arranged as a 6 wheel center drop with the gear box on one end and the other end driving 1:1 off the center axle. Sounds like that's just over 10.1fps to me but I am pretty tired right now.

That meet your expectations?

I've got the double sprockets and the #35 chain with link kits.
I've got 10 single stage Stackerboxes.
I -may- have some 26 tooth sprockets on some used tires if not I'll need to order those.
I've got some sprocket spacers for the AndyMark tires.

Re: SD540 Motor Controller
 

If you really want to go overboard on these controllers go 4 wheel, your choice. Otherwise looks absolutely fine to me. Realistically there will be more variance in "aggressive" driving than from any individual design choice.

Re: SD540 Motor Controller
 

To be clear, since I described one side of a potential drive train, when you proposed going even further with 4 wheel you would end up with a robot with 8 wheels total. 4 on the floor at any one time and 2 elevated at each end.

I agree that the driving style is very important and I only have 3 pairs of 4" AndyMark plaction tires, 12 bearings of the 20 I have on hand, and need to order sprockets because I only have 4x 24 tooth sprockets on my 8" used mechanum wheels.

So there's going to be a short blocking delay while I wait for the few little parts I need to do this with just 6 4" wheels total. I am not entirely blocked because I can still start putting things together.

Frame dimensions or wheel spacing?

Re: SD540 Motor Controller
 

I meant 4wd total (2 per side-more turning scrub=more motor work). Honestly the number of wheels isn't that important. Just use whatever you have on hand.

Re: SD540 Motor Controller
 

I will emulate an AndyMark wheel spacing and frame. Thinking about ways to rig the frame so it can drive on 4 or 6.

Aside from that: 8 wheel with 4 down has as much scrub as 4 wheels plus additional chains and losses but I agree it is just a bit more than necessary to test this.

Re: SD540 Motor Controller
 

Consecutive posts because of the time between them:

Orders for the few missing pieces have been placed.
I will start some assembly this weekend.

Re: SD540 Motor Controller (**VIDEO**)
 

In Talon 540's workshop, we shot a short video of our robot running with SD540's, which you can view here: http://youtu.be/9lq6U3EpyTg

There are a total of six SD540 motor controllers on this robot: four for the mecanum wheels, one for the lift, and one for the pneumatic pump.


They worked like a charm! Our team highly suggests you switch to SD540's for the 2016 season competition and onward! The manufacturer, mindsensors, has their main web page at: http://www.mindsensors.com/

Re: SD540 Motor Controller (**VIDEO**)
 

Since you have these on a robot already.
Also since I will be travelling to Toronto next week till the weekend.
Additionally I will be judging NJ FLL this weekend.

Would you mind measuring the heat sink temperature during operation if you can find the necessary tools?

I'll keep working on slapping my parts together as I need to do that anyway for something else.
So far I've welded up dead axles and wired up a control system.

Re: SD540 Motor Controller (**VIDEO**)
 

It would be good to monitor the (average) motor currents at the same time.

Re: SD540 Motor Controller (**VIDEO**)
 

While I do have the RoboRIO PDP laying around I don't have a RoboRio yet to connect to it. I haven't tried to do CAN with the PDP to the cRIO 4 slot or 8 slot that I do currently have and have been assembling.

So when I get this assembled I'll have to do that some other way unless the RoboRIO arrives by the time I get that far.

It looks vaguely like that Talon540 robot had a RoboRIO on it. So perhaps they could grab that data.

Re: SD540 Motor Controller (**VIDEO**)
 

Just out of curiosity, are you affiliated with mindsensors.com in any way?

If you are affiliated with mindsensors, it seems slightly disingenuous to refer to yourself/your team as a third party without a stake in the game. This is especially true when it comes to endorsement of a new product that serves a critical role and has no competition heritage.

I am in no way accusing you of not doing due diligence or appropriate testing, or questioning your results, but I think it's important for teams to know whether testimony they are basing their purchasing decisions on is coming from an end user or essentially from the inventor(s)/vendor.

Re: SD540 Motor Controller (**VIDEO**)
 

Their team helped to design them and from that seems like they help build them as well.

Re: SD540 Motor Controller (**VIDEO**)
 

Just to share - I have nothing to do with MindSensors or their team.
I merely like the idea of competition for the pricing of FRC motor controls.
It's easy to go back through my post history to show that I have built other controls in the past and expressed public interest in the matter on this forum.

To be fair I also bought 2 Sparks as well.
This is not a Team 11 thing either.
It's just little old me being curious.
I have my own parts to build FRC robots so I don't have to impact Team 11 or 193 operations to do this.
I also have my own machine tools.

At the moment I am planning on doing the temperature and current measurements with an Arduino based data logger but I have more development boards than I care to discuss so I could do this with something more powerful. I will likely use a Dallas 18B20 for the temperature measurement with it installed in a steel cartridge in direct contact with the ESC heatsink and a either a TI or Maxim chip for the current measurement using a current sense resistor of a value I will disclose. It's likely the current sense resistor will be less than 1mOhm right now. I need to disclose that because it has a slight impact on the motor circuit.

Re: SD540 Motor Controller (**VIDEO**)
 

Is it too much to ask if one of the Talon SRX's or Victor SP's to act as a point of reference?

As long as the temperature data is measured at the same output current, the value of the current sense resistor does not matter. The losses in the controller are related to the characteristics of the switch devices used (MOSFETS?), how they are driven by the circuitry in the controller, the switching frequency and the output current. As a user, one would only have control over the output current.

Re: SD540 Motor Controller (**VIDEO**)
 

I don't have either to use as a reference currently.
AndyMark is sold out of the Victor SP.
I can get it here:
http://www.robotmarketplace.com/prod...-VICTORSP.html

At some point I have to point out that the more parts I have to accumulate on short notice the higher the unplanned cost to me of this exercise. I don't really need these chassis until well after build season outside of this. However I will entertain this because I probably will buy at least 2 of the Victor SP sooner or later. I do have the older gray Jaguar, black Jaguar, Victor 888 , Victor 884 and Talon SR (not the SRX).

Here are the constraints of doing this with a proper Arduino and the hardware I have planned:

1. The DS18B20 has variable bit resolution measurement. The more resolution the longer the readings take. I intend to run it at the fastest of 9bit resolution at 0.5C resolution. This means I need to wait likely more than 75ms to get a temperature from it. After issuing the request it can be configured to be non-blocking so I can go off and do other things then check back for the reading.

2. I will likely use either the A/D of the Arduino which for the Mega2560 is 16 channel analog muxed 10bit or something like the MCP3008/MCP3208 like that found on the Propeller ASC+ from Parallax. With the current sense resistors as I plan them this should give me something around a 0.1A resolution for the current. I would figure these are not super high-end A/D so some error is to be expected but most of the error I hope will cancel by being consistent across all measurements. The current sense resistors are high enough wattage that a complete stall shouldn't cause them to fail but likely will rail the current reading. I am going to assume we won't be trying to run the motors consistently at 95A or more.

3. The AdaFruit Data Logging shield provides a DS1307 RTC and access to SD card storage. I can also go down the route of this: https://www.parallax.com/product/27937

Since the current PDP model can only report current as fast as 25ms over the CAN bus connection to the RoboRIO, the only part of this I think is a bit slow is the DS18B20. No matter how fast my CPU/MCU that 75ms is pretty slow but thermally the heatsink mass is not so small that I think we need to be all that fast reading temperature.

4. My initial thought is to store the 2 temperatures and the 2 currents packed.
9 bits (temp) + 9 bits (temp) + 10 bits (current) + 10 bits (current) = 38 bits
Stored as 4 bytes and some bytes for any time stamps.
A trivial amount of code can unpack that and dump it into Excel.

Re: SD540 Motor Controller
 

Let's say someone wanted to test these new controllers. I have access to something that will read the temp. My question is how do I get the current readings off the PDB through the CAN bus? is it as simple as accessing the web based monitor?

Re: SD540 Motor Controller
 

Can you read the heatsink temperature(s) with the RoboRIO with whatever you have (does it have an analog, I2C, SPI output)? If you can you should be able to get the current and the temperature together and log or display it with some coding.

If I had the RoboRIO laying around on a robot with the necessary accessory this would be a fine way to do it.

In Java:
http://wpilib.screenstepslive.com/s/...ribution-panel

In C++:
http://wpilib.screenstepslive.com/s/...ribution-panel

In LabView (see GetPDPCurrents):
http://www.fightingpi.org/Resources/.../LabVIEW.shtml

For the cRIO in general there's some information on National's site about using the DS18B20.
For I2C temperature measurement one might use this: https://www.sparkfun.com/products/11931
Never tested any of this temperature reading stuff on the RoboRIO.

This will help with writing the data you collect out:
http://www.chiefdelphi.com/forums/sh....php?p=1437880

If you do manage to test this please do post the results because the scope of work for me to do: it seems to be growing :).

Re: SD540 Motor Controller (**VIDEO**)
 

A Talon SR would be a good reference too.

Re: SD540 Motor Controller (**VIDEO**)
 

LOL if you had written that about an hour ago ;)
2 Victor SP are on the way to me.

Re: SD540 Motor Controller (**VIDEO**)
 

With all the facilities and parts you have mentioned in your previous posts, I go a serious case of "shop envy". It is now a bit worse :o

Re: SD540 Motor Controller (**VIDEO**)
 

At the rate of accumulation I have 8 Lowes 12 gallon plastic totes filled to the very top in storage. It got to the point I couldn't remember my inventory so I have an inventory spreadsheet. It's not quite as expensive as one might imagine: as I have been accumulating parts for years and only accelerated in recent months. I cleaned out quite a few MicroCenters nationwide after giving everyone several months and a ChiefDelphi thread to beat me to it. MicroCenter discounted most of the AndyMark parts down to 75% off. I routinely hit AndyMark's Tuesday deals. I'm also often the reason a few of you aren't winning your eBay auctions the last few months ;) and at least in a recent case that means I sponsored a team or so indirectly.

It's not just for me, at least I hope not, I am working towards setting up a MakerSpace with FRC resources available. Hence my growing portable MaxNC toolset with the T2 lathe and 10 mill. I am also doing modifications and repairs on them such that if someone breaks them I can fix them cheap and easy.

This is why I was going to build some robots anyway. I will be using smaller final robot dimensions when I get there. I want mine to fit in the largest TSA approved hardshell suit cases so I can take the robots and my portable CNC tools safely more places. This is more an educational exercise out of my pocket than a competitive exercise. It's just not practical for the most dedicated students to learn CNC and programming in 6-10 weeks and the high cost of CNC entry is daunting just to get to a point you realize you don't know G-Code from Rhino VBA ;). (For anyone that points out the MaxNC machines are glorified Sherline/Taig machines: cutting wax for someone that knows no better is just as good on 1/3HP as it is on 10HP. Sure the feeds change and that just goes to reinforce the critical nature of that change.)

If this doesn't work out I will have to open a new web based FRC retailer :D

Re: SD540 Motor Controller (temperature specs)
 

If you are wondering how the SD540's heat up over time, mindsensors and Talon 540 performed a few tests on one of our old robots.

http://www.team540.com/sd540/

Re: SD540 Motor Controller (temperature specs)
 

That's great! Can we get the drivetrain information that produced those temperatures? Wheels, ratios and motor configurations please. There seems to be a section of your website for it, but that information does not seem to be there.

Re: SD540 Motor Controller (temperature specs)
 

Do you have any thing to show the test conditions such as ambient temperature, motor current. These have a significant effect on the measured value. Test results are meaningless without knowing the test conditions.

Re: SD540 Motor Controller
 

I just realized... I need more caffeine! Apologies for an earlier post, but our robot does NOT use an SD540 for our pneumatics. It was for our lift mechanism.

Man, that's embarrassing. I'll drink some Redbull and be quiet now.

Re: SD540 Motor Controller
 

Will a firmware upgrade be released to remove the "safety feature" that cuts motor output if the input voltage drops below 9.5 volts? The "feature" is a deal breaker for me, as that is a surprisingly easy condition to reach on an FRC robot.

Also, the spec sheet claims the speed controller operates at voltages as low as 6 volts, but this "safety feature" kicks in long before that, so the spec sheet is wrong.

Re: SD540 Motor Controller
 

Since you guys seem to be SD540 experts in this thread, I was wondering if you could comment on the very high output resistance of the SD540 that was measured by CTR in their tests (surely you've seen the results). The voltage drop (power lost) in the motor controller is drastically worse than the competition? Did you guys make a design choice or tradeoff that resulted in this? Or is it possible that CTR just got a bad (or damaged) SD540?

And I'll also echo Chris's question regarding a FW update to modify the 9.5V brownout feature. Could you make this voltage threshold user adjustable in the future so that users could control which motor controllers shut off first? Would it be possible to add a throttling feature to reduce output to 50% when a certain voltage threshold is reached?

http://www.ctr-electronics.com/downl...er-Testing.pdf

Re: SD540 Motor Controller
 

And claiming it's a safety feature makes little sense to me. I can run Victors off a 2S Lipo (7.2-8.4V) and be fine. No safety issue, just the robot only operates at those voltages (say for smaller than FRC robots) but this "feature" makes SD540's worthless in these applications. Despite them appearing to be a better fit because of lower cost. (Performance isn't as critical in this application, cost is more a factor)

Re: SD540 Motor Controller
 

If you are letting down your battery 9.5 V your are basically killing your battery( actually 10.8V that is 1.8V per cell).
Lead-Acid battery will quickly built lead sulfide layers on plates ( no matter what is battery technology and what manufacturer claims)
you are basically screwing up battery and now it will have much high internal resistance so the you will start seeing voltage drop when you try to take out good amount of current.

Re: SD540 Motor Controller
 

Don't think I've seen a robot get through a match without dipping that low in their battery voltage.

Re: SD540 Motor Controller
 

Pretty sure I've seen that on a non aggressively geared kitbot that only weighed 80 pounds... Unless the 9.5V limit only kicks in after a period of time in which case I'd like to see that in the documentation (and still complain because my use case for low cost controllers involves lower voltages anyway)

Re: SD540 Motor Controller
 

I guess a robot that doesn't move would probably keep a pretty high voltage too.