Standard Motor Driver Schematic for FRC
 

Hello!

Recently I've been calculating the cost of our robot, and it is waaay overpriced. Part of the problem is that the rules force you to buy motor drivers from specific companies like VEX, who charge way more that they should. I get that the company has to make a profit, as well as pay for the cost of design, but $60 for a victorSP?!?! It would only cost $5-$25 to make a motor controller with the same functionality.

I hear that the reason why they don't want people making their own motor drivers is because they don't want people making circuits that could break, or build a motor driver that may keep driving even after it stops receiving power from the roboRIO.

My proposed idea:
Create a set of standard and FRC approved schematics so low budget teams can make many more motor drivers for their bot with much less money.

Re: Standard Motor Driver Schematic for FRC
 

The Talon SRX is only slightly more expensive than the Victor SP and has many nice things under the hood including full software control over the CAN bus and the built-in ability to interface with encoders, limit switches, and do PID control.

From a value proposition - and taking into account the typical skill level of high school students - this is hard to beat.

While you are correct that, at heart, a basic FRC motor controller could just be a PWM-controlled H-Bridge, I think there's a lot to like about buying a COTS part versus making our own. The fact that it's COTS, already, gives a lot of advantages when playing by FRC rules in terms of being able to swap them out easily for repair, replacement, or upgrade. I would hate to be in a competition situation, with 15 minutes until our next match, combing over a half dozen custom-made motor control circuits trying to figure out why our robot doesn't move. Plus they're sealed, packaged robustly and compactly, made to interface with standard components and connectors, and offer quick easy tools for changing brake/coast modes, recalibrating, etc.

And to top it off, they can be free for FRC teams through the rookie kit and through yearly product donation vouchers such as FIRST Choice. My team ordered four Victor 888 controllers through FIRST Choice and had the choice of either 2 Talon SRX's or 3 Victor SP's from the PDV, all "free". In addition, we got another two Victor SP's in our rookie kit. That's plenty for a robot drivetrain and mechanisms.

FRC is an expensive competition, but motor controllers are not where I'd peg most of the cost.

Re: Standard Motor Driver Schematic for FRC
 

I'll just leave this here: http://www.amazon.com/REV-Robotics-S...tor+controller

Comes with spare screws and a PWM cable for $45 shipped.

Re: Standard Motor Driver Schematic for FRC
 

Yeah, the VictorSP is the "premium" product in FRC. You pay more for the compact size, conformal coated board, the aluminum heatsink body, etc. If you're looking for a better price/performace ratio, look at the REV controllers.

Re: Standard Motor Driver Schematic for FRC
 

All of the motor controllers from the various FRC approved vendors are priced very, very well for what you get.

Re: Standard Motor Driver Schematic for FRC
 

How would you suggest making this inspectable? The inspectors are not all electrical engineers, and looking over each circuit to make sure it was both correct and safe, even from someone with applicable experience, would take some time, and I've heard complaints on CD before about inspections taking too long as it is. And when one doesn't work, most teams don't have the expertise to properly debug a circuit like that, and finding the expertise to help at an event may be difficult.

Re: Standard Motor Driver Schematic for FRC
 

Since the Talon SRX were part of the KOP as a voucher from Vex, you do not need to account on the CAW for your robot.

Re: Standard Motor Driver Schematic for FRC
 

I don't think too many teams have the resources/skills to make motor drivers for less than the cost of something like the Spark given only schematics.

Even though you might be able to buy all the components for real cheap on Digikey, you don't have a circuit board. Some weird parts like gate drivers might only come in surface mount packages sometimes. Even if you did find all the parts in through hole packages, you need to worry about all sorts of electrical interference issues - the FRC controllers don't have isolated logic and power, so you'd need to be clever with how you laid out your board to prevent transients from messing with the microcontroller.

Then, you'd have to figure out how to program the microcontroller. I have yet to find a through hole microcontroller that supports a direct USB connection, so you'd need to buy some sort of programming board or get really good a surface mount soldering.

Re: Standard Motor Driver Schematic for FRC
 

Unless you started mass producing it would actually be very expensive to too make a motor controller even like the old talons or victors, there is a lot of engineering that goes into them first off. PCBs are very expensive in small quantities, and components are very expensive in small quantities. These PCB's are not necessarily something a home gamer could produce either, you need via's in the board to connect top and bottom traces, as well as plated through holes for that parts to handle the current and connect top and bottom traces. I know this because I work in a circuit board shop.

Re: Standard Motor Driver Schematic for FRC
 

The expected audience for this particular scenario seems very small: a team with a low budget that does not want, or cannot afford, to buy motor controllers, but can buy the discrete components, with the students having access to PCB manufacturing equipment, and who are (will become) skilled in circuit design, component layout, soldering, testing, etc.

If this describes your students, then a home-made motor controller might be an excellent off-season project to develop an intimate familiarity with how they work. I daresay that after the experience they will also gain an appreciation of how much work goes into a motor controller and how much value you get for the $40-60.

When I learned to do woodworking one of my first projects was an Adirondack chair. I found plans online, purchased pine boards, and started marking, measuring, cutting, shaping, sanding, routing, drilling, assembling, gluing, clamping, more sanding, staining, more sanding, etc. I probably spent $100+ in raw materials, and dozens of hours of my time. Then one day I walked into Costco and they had Adirondack chairs for $49 each... :(

Re: Standard Motor Driver Schematic for FRC
 

You would be surprised would students can do. It's really not hard to make motor controllers, I've made them myself before and I'm only in 9th grade.

Although it doesn't seem like it, the point I'm trying to argue is that FRC would be much cheaper if they would give students the ability to create and buy their own motor controllers. When you calculate it, our team has spent hundreds of the dollars on motor controllers.

Just because something is in the kit, doesn't mean it's free.

Re: Standard Motor Driver Schematic for FRC
 

Even if someone were to do the board layout, and get the PCBs fabricated and sold at cost, I would not trust a high school student populating the boards.

Troubleshooting even some of the simplest circuits can take a very long time, and without the right equipment (something a low budget team likely does not have) nearly impossible.

Also, having a 17 amp hour battery connected to a bad solder job is a fire hazard...

Re: Standard Motor Driver Schematic for FRC
 

I applaud your motivation. However, as someone who started making motor controllers more than 30 years ago, I should advise you that making them inexpensive and reliable (at the same time) requires significant attention to details that you have not had time or experience to learn yet.

The lead designers at CTRE and REV watch CD and contribute regularly. They are very smart, experienced people. And they are competing with each other. Good, competitive designs are driving motor controller costs down, and performance up. Maybe you can help one of the competitors do that even better, very soon.

Re: Standard Motor Driver Schematic for FRC
 

I'm not saying I don't think students can do it. But I am saying students of your skill level, especially at your age, are not common. And as others have said, there's so much potential for error and frustration and even danger that I can see why they don't allow it.

When I was in grade 9 I took out a sheet of paper and sketched a schematic for a simple computer featuring a Z80 CPU (with EEPROM, RAM, basic I/O, etc.) Sadly I never got to build it. I applaud your ability and the opportunities you have already taken advantage of.

Well, sure. But there's a lot of things that we spend money on. The entire RoboRio control system, especially with the PDP, is quite pricey. Gearboxes are expensive. Wheels, once you add the hubs, are pricey. And did you see how much the boulders cost this year?! Turns out the motors themselves are actually some of the cheapest components in the robot!

Re: Standard Motor Driver Schematic for FRC
 

Ah, to be a teenager and know everything again. :rolleyes:

It's not hard to make a motor controller.

It's hard to design one that interfaces with standard hobby servo signals, provides sustained performance at 40 amps and occasional transients approaching 200 amps, is proven to perform as advertised so the robot can be certified as following the rules, is rugged enough to withstand the abuse it will take on an FRC robot, doesn't pose shock or fire hazards to its users, etc. It's hard to build one to those specifications without having resources, skills, and experience.

If you're expecting to be able to save "hundreds of the dollars" by building your own motor speed controllers, I suspect you're failing to consider a lot of details.

Re: Standard Motor Driver Schematic for FRC
 

When I was a 9th grader most electronics in the home (radio,television,HiFi) were tube based. Even the sound system in our neighbor's car had vacuum tubes (you had to wait several seconds after turning the car radio on for the tubes to warm up before you could hear any sound).

When your TV or radio got flaky, you'd pull all the tubes out and take them to the corner drug store and test them in the tube-tester kiosk.

For my 13th birthday my parents bought me the RCA Tube Manual. I memorized large portions of it. I designed and built my own audio power amp using push-pull 6L6GC tubes. Almost electrocuted myself when I went to re-heat a bad solder joint and forgot about those 400V filter capacitors in the 5Y3 power supply.

It was a different world back then...

Re: Standard Motor Driver Schematic for FRC
 

What sort of continuous output current was your motor controller capable of? How efficient is it? How durable was it, especially when abused? How long has it lasted? How does it behave during fault conditions (does it fault in a safe and benign way)?

A schematic is only a starting point for a successful piece of equipment. A schematic for a good motor controller will look a lot like the schematic for a bad motor controller. You still need an enclosure to keep the circuit board from shorting to adjacent pieces of metal and to keep the metal shavings out. You will need to have a suitable heatsink. Do you know how to select a heatsink that performs adequately yet is not too big and expensive? The higher the current in the circuit and the higher the edge rate of the switching, the more critical the track layout on the PCB is. The layout of the circuit board suitable for FRC motor controllers will not be trivial. A poorly done layout will have high inductance paths, leading to high surge voltages and possibly destruction of the switching devices. A common cure for high surge voltages is to slow the edge rate of the switching but this causes higher losses and heating and lower efficiency and possibly destruction of the switching devices.

There is already a student designed motor controller out on the market. Test results published on this forum show that it is less efficient than other motor controllers. I have been told that it uses twice as many MOSFETs as other controllers indicating that the devices are not being operated in an efficient manner. It is quite likely that the board layout was not done in an optimum way (see above).


What is your team's time worth? Are you going to propose building your own controller too (because the processors are under $10) instead of purchasing a RoboRio ($435). This is a robot competition, not a motor controller competition.

It is likely that providing just a schematic will lead many teams to disaster. Not all of them will be able to obtain the proper parts and substitute a part that "looks close enough" (yes there is a difference between two parts with the same nominal rating). Most of the parts that will be suitable are "surface mount" types. Most people I have met (including engineers working in the field) do not have the skills needed to successfully hand solder surface mount components correctly.

There is at least one other individual who has posted in this thread who has indicated that they have to professional experience in this field to comment in an authoritative and credible way and they are all saying that there is a lot more to have a successful power electronic circuit than just having a schematic. My background is doing the design and development for motor controllers ranging from 5hp to 1200hp over the last 20+ years. I use many of the same design techniques necessary to make a successful FRC motor controller and it took me (and the others posting here) much longer to learn these techniques than a high school student would have. A few years ago, I visited a startup company that had a microprocessor guru/consultant who sold them on the idea that he could design a complete motor controller for them because he got hold of a generic schematic. I saw their prototypes (as well as the scorch marks on their equipment) and it was pretty easy to see what they were doing wrong. That start up closed down pretty soon afterward.

Re: Standard Motor Driver Schematic for FRC
 

There is a time and a place for saving money. DIY is sometimes the way to do that, but sometimes it is not.

2706 is a new team. We started from scratch last fall so we have had to buy everything new including all our tools, all the stuff on our robot and all the extra stuff we needed for prototyping and testing. Believe me we understand wanting to save money. There were many things we did ourselves in the interest of saving team money. Among them was judicious shopping for parts we could have bought from one popular supplier but found cheaper elsewhere. Motor controllers fall in this category, I think, especially with new controller options on the market now. You can even buy them from Amazon!

Re: Standard Motor Driver Schematic for FRC
 

It takes more time to make custom motor controllers then finding a sponsor or two that will give you enough money to buy them. Its a cool learning experience but a waste of time in a 6 week season.

Re: Standard Motor Driver Schematic for FRC
 

This is a very good point. In one Saturday of concerted effort our team can execute a community bottle drive that raises about $800-1000. You might be able to get even more by pounding the pavement and talking to shops and businesses in the area.

Re: Standard Motor Driver Schematic for FRC
 

I applaud my students who want to learn how to make custom circuits or custom anything. While our team doesn't do it much yet, my understanding is the RoboRio allows for this a lot more than past controllers (I may be wrong, programming/controls is my weak spot)
That being said, these are the things that control a 120 pound robot going fast enough to hurt someone. They also control a huge amount of amperage. I trust my students a lot, but not when it could be something where a mistake could greatly injure someone else.
Further, out of all of our costs, motor controllers are pretty small. Yes, we did dump about $2k into the Talon SRX's when they came out, and I do understand thats a lot of money, but you can easily get away with a couple hundred and still have the Talon SRX and not a cheaper option like the REV one if the options the SRX delivers are important to you
One big thing you're missing too is these are reusable. That was largely a one time cost compared to motors/gearboxes/framing/etc which far exceeds 2k a year.

It would be great to save money in FIRST, but I dont think this is where to look. If money is an issue with a team, look at the structural components as a way to save money. Reusing simple small things like hex clamps, sprockets, or bearings adds up to far more than a few speed controllers.

Re: Standard Motor Driver Schematic for FRC
 

Thank you for bringing this point into the discussion. FRC approved motor controllers are durable.

This year we are running several Talon SRs that we've used in two previous seasons. We also have the same number of new SPARKs, which are on our practice robot. After those have proved reliability we intend to re-use them on future robots. To date we have had no failures of Talon SRs (which are obsolete) or of SPARKs.

Re: Standard Motor Driver Schematic for FRC
 

I think that most people in this thread have summarized the reasons why letting teams make their own motor controllers is not a practical idea, as there are so many things that can happen when hand assembling something to handle this amount of power. Even if 99% of the motor controllers were done properly the 1% of them that fail can cause fire, robots not responding in a controlled fashion, and a bunch of other issues.


Some people might not have realized this, but we have published the schematic for the SPARK at the back of our user guide. We believe that people should be able to learn from the product itself and not just the use of the product. Here is the direct link (PDF) http://www.revrobotics.com/wp-conten...1200-UM-00.pdf

If any student wants to create their own "homebrew" version of the SPARK we encourage you to try, because reproducing is a great way of learning. For a low cost way to make your own PCB's, my friends own Dirtypcbs.com (and regardless of their name make good quality cheap boards)

Re: Standard Motor Driver Schematic for FRC
 

Greg, I didn't know this and I'm actually really happy. It'll at least help me figure out whether it's worth the effort to put together a custom ESC for a project that falls nicely in that gap between what a VexController 29 can drive (which is actually quite a bit more than you'd think) and where I'd use a Spark (I'm cheap, like REALLY cheap) There exist a handful of brushed ESCs from China in that range but, frankly, their english documentation and my knowledge of the Chinese language seem to share the property of being bad/nonexistent.

Re: Standard Motor Driver Schematic for FRC
 

I'm curios but those diacs on the motor out put, are those to protect the motor controller from ESD or from power backfeeding from the motor? Or am I way wrong?

Thanks

Re: Standard Motor Driver Schematic for FRC
 

I highly commend you for this.

Re: Standard Motor Driver Schematic for FRC
 

I'm sure that most of these teams when given the schematic will just arbitrarily place components onto the board layout and hit autoroute. :rolleyes:

There's a reason for everything!

Re: Standard Motor Driver Schematic for FRC
 

Also, the Victor SP was part of that voucher and part of FIRST choice, both of which make it exempt from the CAW.

Re: Standard Motor Driver Schematic for FRC
 

I'm somehow having difficulty picturing a young Ether. The only image that ever comes to mind is the one in the profile.

Re: Standard Motor Driver Schematic for FRC
 

How many of those issues are particular to high current designs? Does something sitting in the 15A constant 30A burst range have to worry quite as much about these issues?

Re: Standard Motor Driver Schematic for FRC
 

It is the interaction of the circuit inductance AND the rate of change of the current that provokes issues (dV = L * dI/dt). Higher currents typically lead to higher values of dI/dT.

At work, I am working on improving a switching power supply where the peak primary current is less than 1 Amp. The person who originally did the PCB layout clearly didn't know how to do it properly. Neither did the person who designed the transformer. The circuit sprays copious amounts of electrical noise.

If one does not have a thorough understanding of how to control the parasitic inductances inherent in the physical construction of a fast-switching circuit, one WILL have trouble with issues such as noise and over/under-shoot. The parasitic elements are not indicated on a typical schematic since they are dependent on exactly how a circuit is physically implemented. It is up to the designer to determine where in the circuit the parasitic elements will be significant and how they can be mitigated. It is not black magic but it takes many years of hands-on experience to be able to do this effectively. Reading a book, attending a class and being smart are not enough.

Re: Standard Motor Driver Schematic for FRC
 

I never said that I intended on magically designing high-powered motor controllers that could survive a nuclear blast with the power of Cadsoft Eagle auto route feature and my amazing newbie mosfet skills.

Instead I'm asking for some sort of a motor driver standard,

There where several situations during the build when we needed a plain on/off type motor controller, so I hooked up a relay board that cost ~$10 (I had it from an earlier build).

But I couldn't use it because of the amount of FRC rules in place.

And knowing Vex, if a motor controller board costs $60, it probably only costs $30-$40 in parts. Of course they still have to pay for labor, shipping, and the design process, but I'm sure the community could create just as good of a motor board as them.

It's a bit of an Apple vs Linux situation. You can buy an expensive Apple computer that 'just works', and the software is completely closed off and protected, so you never have to worry about it. Or you can use Linux, which is free and works efficiently, you would just have to assemble the software yourself, which is slightly more time consuming.

To be fair, I would prefer to use vex motor driver boards, but money isn't free flowing, and the design process is expensive.

Re: Standard Motor Driver Schematic for FRC
 

There is also a monopoly in FRC, where everything promotes VEX and AndyMark. It would be better to start including products from a larger variety of companies, since they can't even keep their own products in stock despite the fact that they know what parts people are probably going to need for competition before the kickoff.

Vex and AndyMark produce parts and then get library support for their specific part. Since they are certified FRC suppliers, they then sell parts for more than their worth because people trust them more.

Re: Standard Motor Driver Schematic for FRC
 

Should anyone doubt this, I'd suggest they direct their attention to the (now thankfully defunct) Jaguar motor controllers, which were made by a professional company who (ostensibly) knew what they were doing and still suffered from all sorts of reliability issues.

Monopoly - a commodity or service in the exclusive control of a company of group.

You just named two companies that's your first issue.

Next you do know Andymark doesn't make any motor controllers they just sell them.

These companies have to make a profit off a small market. You can not expect to have more then a few suppliers for 3,000 teams.

Right now you have a lot of options for motor controllers

Jaguar Motor Controller (Part #s: MDL-BDC, MDL-BDC24, & 217-3367)Talon Motor Controller (Part #s: CTRE_Talon, CTRE_Talon_SR, & am-2195)Talon SRX Motor Controller (Part #: 217-8080 & am-2854)Victor 884 Motor Controller (Part #: VICTOR-884-12/12)Victor 888 Motor Controller (Part #: 217-2769)Victor SP Motor Controller (Part #: 217-9090)

Along with
The mindsensors sd540
And the Rev sparks

That's 8 options for motor controllers which imo is an oversaturated market already.

Re: Standard Motor Driver Schematic for FRC
 

I was looking up the encoders on AndyMark. The encoders they sell are only $20 each when you buy them in bulk (50), and they sell them for less if buy more (it says I have to ask for a quote if more then 50), but they sell them for $40 each.

And I'm sure shipping +$5-10 in profit is not $20.

They also sold every team a base kit that can't even clear any of the obstacles, so that you would then have to buy another base kit or upgrades (Making them more money).

On top of that they knew what this years competition was, and they couldn't even keep Rhino Treads in stock during build. Some supply and demand could be going on.

I know that I'm getting off-track on my own thread, but I'm trying to conserve money for our school.

Re: Standard Motor Driver Schematic for FRC
 

Let's ignore for a moment that BOTH the Talon and Victor are in stock currently.

Let's ignore for a moment that there are at least 2 other companies actively selling ESCs that are legal for FRC applications.

Let's ignore for a moment that there's a handful of grandfathered ESCs that are also legal for FRC applications.

I'm just going to address the fact that you are complaining about the cost of ESCs... Prior to a few years ago our ESCs were stupid expensive. I seem to recall paying $120 a pop for a Victor that was much larger, not conformally coated and not as linear. And you know what? They were still worth it then. I have never had a properly connected [1] Victor die on me. 12 years of robots, many years with practice bots, numerous test beds and demo robots... Never. I've used probably 200 Victors in the last 12 years and NEVER had a failure. I'm sure you could find something that claims to have the same specs as a Victor for about $40 on HobbyKing today, but to me the extra $20 I pay to order a product that has that kind of track record is worth it.

And if you don't care about that track record [2], there's $45 SHIPPED ESC that's legal and you're not going to find an off the shelf ESC for much less anywhere. [3]

But, for fun, let's do a thought experiment on if they were legal. I would NEVER pick a team that used custom built ESCs for their drive system. Honestly, I have qualms about picking a team that uses SD540s or Sparks in their drive system this year.[4] The average FRC team can't reliably build bumpers. An ESC is at least an order of magnitude more complicated, I have no faith in their ability to do that reliably either.




Ok, now we can bring back the 3 other points...Would building an ESC be a cool summer project? Sure. Would it be worthwhile? Absolutely. Can you do better than commercial companies? Maybe, maybe not. Is there some conspiracy by VP and AM to increase profits by gouging prices on ESCs? If you really believe this, who is your tin foil hat supplier?

Seriously though, you wanna build your own ESC? Cool, do it. But don't whine about how the only reason you're not allowed to run it in competition is so AM and VP can make more profit. [5]



-s


Edit: Addressing follow on post...

1: That's par for the course for electronics. Larger orders are cheaper. You also have to take into account that stocking and inventorying parts isn't actually cheap. I'd also bet AM has much better support for if you order 3 encoders and one of them comes DOA. A lot of companies will sell you small quantities but they don't care you exist unless you order 10000 units a year.

2: You're right, the KoP frame didn't cross the obstacles. To which I have two responses - this is a freaking engineering competition, try doing some engineering and don't expect half of the game to be solved for you out of the box. And second, yes. I think it's been discussed numerous times that AM didn't know the game until the kitbot had already entered manufacturing and it was too late to change things.

3: VexPro ran out of gears... GEARS. Which do you think is easier to manufacture and stock, a complicated high cost assembly with limited use or a freaking 54T .5" hex bore gear? Go ahead, while you think that one through I'll wait. ... back? Good, so yeah, see again, inventorying is expensive and expecting AM to keep 1000 Rhino drive kits in stock on the off chance teams would want it is messed up and would actually only drive prices up more. Furthermore, they were a new product so production probably was still ramping up and had issues [6].

And furthermore, on 2 and 3, have you MET Andy Baker? Dude ain't trying to profit off of the backs of teams.


[1] I had 2 fail at one point, because I hooked the output of one into the input of another due to mis labeled wires in the depth of a robot.

[2] Though, honestly, I trust Greg not to put out a shoddy product, I'm CAN bus this year or I'd probably have used a few Sparks outside of my drive system.

[3] I've looked, extensively.

[4] Seriously, nothing against those products, but I've lost too many matches due to partners sitting dead on the field, I want that record of reliability. This may change next year or w/ more testing.

[5] And AM/VP would be a duopoly... And I guess since there's at least 3 manufacturers it'd be a.. triopoly?Idk, I don't think that's a word, I think they just call that a competitive marketplace.

[6] Like stress issues on the pulleys... which they fixed.

Re: Standard Motor Driver Schematic for FRC
 

I'm going to correct you on just this one point, since there will be plenty of people better able to address your concerns about motor controllers specifically. This year was the first time that FIRST revealed elements of the game to certain suppliers prior to kickoff. The only thing that Andymark or VEX knew prior to kickoff was that there would be obstacles for the robots to traverse and (I think) that it was a ball game. Nothing was disclosed of the size, type, or nature of the obstacles or balls. Accordingly, Andymark adjusted the Kit of Parts chassis to include 6 inch wheels rather than the 4 inch versions that have been provided for the previous two years. They did not know enough to guarantee that they would be able to move a sizable stock of Rhino modules, pneumatic wheels, etc. The same thing applies to VEX and West Coast Products.

The FRC suppliers have done an excellent job of handling supply shortages for the past few years. We recently purchased a set of hex shaft collars from Andymark and received a set of VEX collars - still in vex packaging - in the Andymark shipment. These companies do everything they can to help make sure your robot gets completed in time and I have nothing but good things to say about them.

Re: Standard Motor Driver Schematic for FRC
 

LOL. You don't know how good we have it now in FRC. If you were around back in the early 2000's and compared what we have now with what we had then, you'd personally thank every single supplier that makes this competition more accessible to teams around the world. They've changed FIRST in a great way. The majority of teams don't have the skillset nor do they want to waste time building their own motor controllers (mine included.)

Instead of complaining on Chief Delphi about how much stuff costs, you could be spending time actively fundraising so that your team can afford more. Get your teammates to do it too. Little donations all add up. It's no secret that it costs money to compete. Work on fundraising so your team can purchase a few things.

Re: Standard Motor Driver Schematic for FRC
 

Andymark doesn't get specific game information ahead of time any more than any team does. I believe Andy said they were told there would be obstacles in this game or something like that, which inspired the rhino tracks. Makes it hard to design for specific obstacles. It also makes it hard to pre-buy enough stock to satisfy the demand of 3000 teams. It's obvious after kickoff that there will be a run on pneumatic tires, or banebot wheels, or whatever the hot item is. It's never obvious before kickoff.

On the cable, I suspect you didn't actually specify the encoder correctly on US-Digital. When you specify one spacer and centering tool per encoder, the price per 50 is $28. And then you add a $5 cable on top. Andymark and Vex don't have a huge markup. They can't because if they did, they couldn't compete with other suppliers like Robot Marketplace, Robotshop, Mouser, Digikey, various industrial supply houses, or any random Joe that sets up an EBay or Amazon shop. It's called capitalism.


Honestly, the best way to save money for your school is to not break things so you can save what's salvageable from year-to-year. After about 3-4 years of not exploding motor controllers or melting motors, you'll have plenty for whatever robot you're going to build. A few more years and you'll have plenty for two robots. The best way to save money in a particular season is to CAD and actually design your robot so you can minimize buying the wrong thing or express shipping something you need in 2 days before competition or bag.

Re: Standard Motor Driver Schematic for FRC
 

Oh my gosh, but 1998 - early 2000s. I don't remember when we could finally buy stuff from somewhere other than Small Parts, but it was amazing. I mean, if you want to talk about a monopoly, THERE was a monopoly....

Re: Standard Motor Driver Schematic for FRC
 

A good friend of mine, Bill French has some musings on building his own motor controller:

Just as an addendum, the reason he had to take a sawzall to it was one of the Mosfets on it had failed in the closed condition resulting in a motor stuck spinning at full throttle forward.... better be quick with the e stop. The sawzall was to cut the burnt up mosfet off the board in an expedient fashion in order to get back on the track more quickly.

Re: Standard Motor Driver Schematic for FRC
 

This is not a bad analogy.

If you were doing a mission critical presentation, say to the CEO of some big company, which would you rather use?

I would rather have something that "just works". I would like to know that when I boot up my laptop and start my presentation, it will work. That my laptop won't fail on me because, oops, apparently I didn't do that DIY upgrade correctly and I accidentally broke it. That if I do have a failure, I can say "oops, oh well, can I borrow someone else's laptop?"

And even if you say "I'm smart and I can guarantee mine wouldn't fail like that", then put yourself in different shoes. You're running a conference with hundreds of attendees. Which would you rather each of them be using? Can you trust everyone else to be as smart as you?

Re: Standard Motor Driver Schematic for FRC
 

Absolutely. See Phil's reply.