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#31
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Re: Standard Motor Driver Schematic for FRC
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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. Last edited by philso : 17-03-2016 at 00:16. |
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#32
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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. |
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#33
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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. Last edited by ProfessorAlekM : 17-03-2016 at 10:13. |
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#34
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Re: Standard Motor Driver Schematic for FRC
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Last edited by Oblarg : 17-03-2016 at 10:12. |
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#35
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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. |
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#36
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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. |
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#37
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Re: Standard Motor Driver Schematic for FRC
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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... Quote:
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. Last edited by Andrew Schreiber : 17-03-2016 at 10:53. |
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#38
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Re: Standard Motor Driver Schematic for FRC
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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. |
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#39
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Re: Standard Motor Driver Schematic for FRC
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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. Last edited by Ryan Dognaux : 17-03-2016 at 10:53. |
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#40
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Re: Standard Motor Driver Schematic for FRC
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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. |
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#41
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Re: Standard Motor Driver Schematic for FRC
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#42
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Re: Standard Motor Driver Schematic for FRC
A good friend of mine, Bill French has some musings on building his own motor controller:
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#43
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Re: Standard Motor Driver Schematic for FRC
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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? |
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#44
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Re: Standard Motor Driver Schematic for FRC
Absolutely. See Phil's reply.
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