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Talon SRX Breakout Boards by: marshall
This is a whitepaper written by Teams 5190 and 900 about the creation of a Talon SRX Breakout Board.
This paper documents our first attempt at a collaborative approach to PCB design and manufacture between two North Carolina FRC Teams. Our aims were to educate students about working with PCB layout and design software and of course to create a Talon SRX breakout board that we felt had all of the features we wanted.
If anyone has questions then let us know. I want to personally thank Team 5190 for reaching out about this project and getting it started. You folks are amazing and we’re thrilled to be working with you.
Wonderful! The overview of the design process was very helpful. I didn’t know such a handy software came in the virtual KOP.
What made you go with an op-amp circuit for the 5c to 3.3v conversion over something like a mosfet? I’m unfamiliar with industrial electronics so it seems odd to me.
We thoroughly enjoyed working with the folks from 900.
What started out with a quick email question turned into a collaborative effort that embodies many of the fundamental tenets of FIRST. What a great experience for me and our students to get to know and learn from a great group of people who are right down the road.
One thing that helped us is that I use Altium in my day job, so the learning curve for a (very) powerful tool was a little less steep for the students to climb. They took to it rather well and were quite enthusiastic to learn.
Having a buffer with a high resistance divider input reduces the load on the analog circuit being measured and provides a strong signal for the ADC input of the controller. A voltage divider could be used without any buffer circuit, but then the analog input of the motor controller would have to handle the load. This mainly is an issue with ADC acquisition time when you are measuring a circuit with high resistance that is changing at a high rate.
Honestly it’s not a problem we’ve run into at all. You can set it via code so the button is nice but we just don’t need it. We didn’t use these boards this year because we didn’t have any encoders that we felt we needed to use them for but 5190 did and they worked great (though I suspect a Rev 2 will be coming!). We’d like to see them made available to the larger FRC community but we need a supplier for them.
Awesome, I hope people continue to make custom circuit boards in the future. I have been a little afraid to design my boards with Altium since you never know if they’re going to give donations in following years. I guess I should have the same worry about SolidWorks, so perhaps it’s a little unfounded worry.
I released a board prior to build season for an AS5040 sensor that didn’t have grounded vias so you didn’t have to worry about isolation. IIRC, I changed the mounting dimensions to something that made sense as well.
It’s true but if you get them from the part manufacturer or supplier then they tend to be good.
I’d love to create an altium library with common FRC parts but I don’t have the time to invest in it. I hope that part mining becomes easier down the road though and EDA packages start to integrate search in collaboration with shops like Mouser and Digikey… would be nice to troll for parts and be able to import them too.
Regarding the library models, what I typically found is that the component I was using wasn’t in the library.
I’ve used a lot of DC-DC converters,circular connectors, fiber transmitters and receivers; things that aren’t mainstream, but are needed.
I also found that I could solder 1206 SMT patterns if I made my own pattern with longer pads. I am sure the off the shelf libraries work fine for the professional machines - I was working low quantity prototypes.
Thanks for the google pointer … I will probably have more questions.
I looked into a number of Altium related items; honestly, their library capabilities appear to be a brick wall (perhaps a rock wall!). Most of the library information I can find is targeted at Altium version 10 or below. Their present distribution is at 16. Is anybody really using this package???
I am concentrating on free software versions. The first I ran into was geda. Gnu based and primarily intended for use on Linux systems. I am still working on getting up to speed on both! I think this has the highest payoff if I can make the Windows to Linux transition.
What I have been the most productive with is KiCAD. Free … windows based … able to create library entries, able to associate footprints with components. KiCAD is definitely clunky to use, although working through one design gets the user up to speed pretty fast.
I was able to do this in 3 or 4 evenings having never used the package, but with several years of CAD experience … several years ago!
QFT. You can also upload the native Eagle .brd files to Oshpark for ordering PCBs, allowing you to skip making CAM files. This lets me upload 8 or 9 times per design, as it shows you a preview of what it will look like and lets you catch errors or sketchy situations easily.
That being said, making custom parts in Eagle can be arduous if you’re not used to it. There are no convenient dimensioning tools like Solidworks’ Smart Dimension. You either have to go by the dimension grid, or type in coordinates for each part manually.