7 ms·

Awesome work! It's really cool to see this from a high school team. While designing liquid rocket avionics [1] at Purdue Space Program, we went with a BotBlox s

Awesome work! It's really cool to see this from a high school team. While designing liquid rocket avionics [1] at Purdue Space Program, we went with a BotBlox switch that cost $80 apiece [2], which I thought was ridiculous. My proposal to in-house the Ethernet switch was vetoed because I was a filthy CS student (joke) and my co-lead (the electronics guy) said it wasn't worth our time designing and validating such a part. An Ethernet switch for $6.9 directly from JLCPCB is pretty incredible, thank you for making this product sector a tiny bit better :) [1] https://sagarpatil.me/projects/cms-avi-hw https://sagarpatil.me/projects/cms-avi-hw [2] https://botblox.io/products/micro-gigabit-ethernet-switch https://botblox.io/products/micro-gigabit-ethernet-switch

byran 2y ago
"making this product sector a tiny bit better" is exactly what MUREX is all about :). It's something we honestly believe in and will continue working on as long as we're around. Believe it or not, the Ethernet Switch was the least problematic piece of hardware in our tech stack! If you want to take a look, we have our other boards in the docs as well. Your rocket is so f*ing cool as well! I definitely want to do something similar in college.
- sr-latch 2y ago
  Ok this is sick, I love the philosophy of your team. I'll be strongly considering your CM4 carrier and ESC to integrate into future designs. Also thank you, I've loved working on the PSP rocket! Bi-propellant rocketry is a pretty rare to do as an undergraduate, and you should consider applying to these schools if that's something that motivates you: - Purdue: https://purdueseds.space/ https://purdueseds.space/ - Berkeley: https://www.berkeleyse.org/ https://www.berkeleyse.org/ - UCLA: https://www.rocketproject.seas.ucla.edu/ https://www.rocketproject.seas.ucla.edu/ - Georgia Tech: https://www.gtspaceprogram.com/ https://www.gtspaceprogram.com/ - ERAU: https://daytonabeach.erau.edu/about/labs/rocket-laboratory https://daytonabeach.erau.edu/about/labs/rocket-laboratory This is a non-exhaustive list of schools I know that have undergraduate-run liquid rocketry programs.
  - knappe 2y ago
    I'd add https://www.colorado.edu/studentgroups/cobra/ https://www.colorado.edu/studentgroups/cobra/
  - tejtm 2y ago
    and Portland State University! https://www.pdx.edu/psu-space#psas https://www.pdx.edu/psu-space#psas Undergrads, not catching on fire in space!
  - byran 2y ago
    Thanks everyone! Noted deeply in the heart. :)
minetest2048 2y ago
I think you should submit your project page [1] as another show HN, I found it to be interesting Some thoughts: - Agreed with not using I2C, I2C has been identified as a root cause in several cubesat mission failures: https://pure.tudelft.nl/ws/portalfiles/portal/10531886/art_3A10.1007_2Fs12567_016_0138_0.pdf https://pure.tudelft.nl/ws/portalfiles/portal/10531886/art_3... and https://webapps.unsworks.library.unsw.edu.au/fapi/datastream/unsworks:64091/bin2ba838a3-66f0-4790-8a76-2ab574d77723 https://webapps.unsworks.library.unsw.edu.au/fapi/datastream... (yes clock stretching is evil). I2C should be banned for multi board communication - Classic CAN have very small 8 byte MTU with frame preemption, which is actually useful for its intended purpose of time critical automotive data transfer. If that 4 byte brake packet is blocked by a 1500 byte packet then your car will crash and explode. But the tradeoff is that this makes it very slow for bulk data transfer
- RedShift1 2y ago
  Wtf, I2C in a satellite!? I am by no means an electrical engineer or know anything about doing stuff in space but it seems absolutely obvious to me if you require any sort of communication, that you use differential signaling. Even on earth you can have interference, in space with all its radiation it's guaranteed. I'm surprised anything worked at all with I2C.
  - semi-extrinsic 2y ago
    Yes, I2C is technically meant for intra-board use. But it works surprisingly well over large distances if you avoid daisy chaining and run one cable to each target. If you use multiple identical target chips you need to route everything individually to a central MUX anyways. As an example, the Nintendo Switch used I2C over a ~2m cable to communicate between the controller and nunchuck. Worked fine even in noisy household settings with wifi and microwaves and whatnot. At work we've used sensors for data logging that communicate using I2C over distances more than 20 meters, using plain Cat5 cable.
    - phero_cnstrcts 2y ago
      Do you mean the Wii?
znpy 2y ago
Worth noting though that the switch you linked claims to be a gigabit switch while the switch from murex is 100Mbpbs. Not sure if that justified the price difference
wal5hy 2y ago
Congratulations MUREX Robotics team, great job! There are products at different price points on the market, for example this 55x55mm switch from my company Brainboxes[1] is sub $50. We choose that size so that we could also produce a gigabit option with the exact same footprint. We opted for microMatch[2] style connectors as you can get board to board as well as board to cable options. Your co-leads decision to buy-in is quite common, as you can reduce time to market and also not have to manage the component lifecycle if you go with an off the shelf option. [1] https://www.brainboxes.com/product/pure-embedded/pe-505 https://www.brainboxes.com/product/pure-embedded/pe-505 [2] https://www.te.com/en/products/brands/micro-match.html?tab=pgp-story https://www.te.com/en/products/brands/micro-match.html?tab=p...
- byran 2y ago
  That's a sick board! If we had found that before we made it, maybe would have just used this board haha. What is "buy-in"? Is it meaning us using JLCPCB to buy and assemble the chips?
  - wal5hy 2y ago
    Thanks! Like yourselves we saw a clear niche for a ultra-reliable small embedded board suitable for robotics and other space constrained systems. I'd be very happy to send you one of our products to compare, i'll message your team email. By "buy-in" I was referring to the parent comment and how the electronics guy chose to buy-in a pre-made module rather than design their own.

byran 2y ago

"making this product sector a tiny bit better" is exactly what MUREX is all about :). It's something we honestly believe in and will continue working on as long as we're around. Believe it or not, the Ethernet Switch was the least problematic piece of hardware in our tech stack! If you want to take a look, we have our other boards in the docs as well. Your rocket is so f*ing cool as well! I definitely want to do something similar in college.

sr-latch 2y ago
Ok this is sick, I love the philosophy of your team. I'll be strongly considering your CM4 carrier and ESC to integrate into future designs. Also thank you, I've loved working on the PSP rocket! Bi-propellant rocketry is a pretty rare to do as an undergraduate, and you should consider applying to these schools if that's something that motivates you: - Purdue: https://purdueseds.space/ https://purdueseds.space/ - Berkeley: https://www.berkeleyse.org/ https://www.berkeleyse.org/ - UCLA: https://www.rocketproject.seas.ucla.edu/ https://www.rocketproject.seas.ucla.edu/ - Georgia Tech: https://www.gtspaceprogram.com/ https://www.gtspaceprogram.com/ - ERAU: https://daytonabeach.erau.edu/about/labs/rocket-laboratory https://daytonabeach.erau.edu/about/labs/rocket-laboratory This is a non-exhaustive list of schools I know that have undergraduate-run liquid rocketry programs.
- knappe 2y ago
  I'd add https://www.colorado.edu/studentgroups/cobra/ https://www.colorado.edu/studentgroups/cobra/
- tejtm 2y ago
  and Portland State University! https://www.pdx.edu/psu-space#psas https://www.pdx.edu/psu-space#psas Undergrads, not catching on fire in space!
- byran 2y ago
  Thanks everyone! Noted deeply in the heart. :)

minetest2048 2y ago

I think you should submit your project page [1] as another show HN, I found it to be interesting Some thoughts: - Agreed with not using I2C, I2C has been identified as a root cause in several cubesat mission failures: https://pure.tudelft.nl/ws/portalfiles/portal/10531886/art_3A10.1007_2Fs12567_016_0138_0.pdf https://pure.tudelft.nl/ws/portalfiles/portal/10531886/art_3... and https://webapps.unsworks.library.unsw.edu.au/fapi/datastream/unsworks:64091/bin2ba838a3-66f0-4790-8a76-2ab574d77723 https://webapps.unsworks.library.unsw.edu.au/fapi/datastream... (yes clock stretching is evil). I2C should be banned for multi board communication - Classic CAN have very small 8 byte MTU with frame preemption, which is actually useful for its intended purpose of time critical automotive data transfer. If that 4 byte brake packet is blocked by a 1500 byte packet then your car will crash and explode. But the tradeoff is that this makes it very slow for bulk data transfer

RedShift1 2y ago
Wtf, I2C in a satellite!? I am by no means an electrical engineer or know anything about doing stuff in space but it seems absolutely obvious to me if you require any sort of communication, that you use differential signaling. Even on earth you can have interference, in space with all its radiation it's guaranteed. I'm surprised anything worked at all with I2C.
- semi-extrinsic 2y ago
  Yes, I2C is technically meant for intra-board use. But it works surprisingly well over large distances if you avoid daisy chaining and run one cable to each target. If you use multiple identical target chips you need to route everything individually to a central MUX anyways. As an example, the Nintendo Switch used I2C over a ~2m cable to communicate between the controller and nunchuck. Worked fine even in noisy household settings with wifi and microwaves and whatnot. At work we've used sensors for data logging that communicate using I2C over distances more than 20 meters, using plain Cat5 cable.
  - phero_cnstrcts 2y ago
    Do you mean the Wii?

znpy 2y ago

Worth noting though that the switch you linked claims to be a gigabit switch while the switch from murex is 100Mbpbs. Not sure if that justified the price difference

wal5hy 2y ago

Congratulations MUREX Robotics team, great job! There are products at different price points on the market, for example this 55x55mm switch from my company Brainboxes[1] is sub $50. We choose that size so that we could also produce a gigabit option with the exact same footprint. We opted for microMatch[2] style connectors as you can get board to board as well as board to cable options. Your co-leads decision to buy-in is quite common, as you can reduce time to market and also not have to manage the component lifecycle if you go with an off the shelf option. [1] https://www.brainboxes.com/product/pure-embedded/pe-505 https://www.brainboxes.com/product/pure-embedded/pe-505 [2] https://www.te.com/en/products/brands/micro-match.html?tab=pgp-story https://www.te.com/en/products/brands/micro-match.html?tab=p...

byran 2y ago
That's a sick board! If we had found that before we made it, maybe would have just used this board haha. What is "buy-in"? Is it meaning us using JLCPCB to buy and assemble the chips?
- wal5hy 2y ago
  Thanks! Like yourselves we saw a clear niche for a ultra-reliable small embedded board suitable for robotics and other space constrained systems. I'd be very happy to send you one of our products to compare, i'll message your team email. By "buy-in" I was referring to the parent comment and how the electronics guy chose to buy-in a pre-made module rather than design their own.