Show HN: We made a small and cheap network switch

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

[2] https://botblox.io/products/micro-gigabit-ethernet-switch

minetest2048 · 2 years 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_3... and 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 · 2 years 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.

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Hello9999901 · 2 years 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 · 2 years 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/

- Berkeley: https://www.berkeleyse.org/

- UCLA: https://www.rocketproject.seas.ucla.edu/

- Georgia Tech: https://www.gtspaceprogram.com/

- ERAU: 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.

wal5hy · 2 years 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

[2] https://www.te.com/en/products/brands/micro-match.html?tab=p...

Hello9999901 · 2 years 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?

znpy · 2 years 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

Nice project and good work.

The only thing is it doesn't address a new or existing market as-is because it competes with what already exists. For example, a TrendNet 10/100 compact switch (not a hub) goes for $7.31 including shipping on eBay and it comes with a case and a power supply. Decommodifying a product requires finding niches where there is demand like automotive, aerospace, military, or marine applications. Until roughly 2020, 2.88 MB 3.5" floppy drives were in-use primarily in industrial and turnkey commercial systems long after they disappeared from desktop computers. Dinosaur technologies can live on for a very long time, often in critical systems deemed too expensive to replace.

Keep pushing forward, learning, and getting better.

Btw, if someone made a:

- 48 port 10GBASE-T (802.3an-2006) POE++ (IEEE 802.3bt-2018) 960W-1600W+ (3422W would be the upper limit for type 4)

- L2 (at least) switch

- unmanaged to fully-managed (but no cloud features)

- 4 100GBASE QSFP28 uplinks (unpopulated)

- dual, hot-swappable PSUs

- 2 models: Ports facing either forward or reverse

- 19" 1U half rack depth, and wall mountable

- Most importantly: doesn't sound like a jet engine under full load by leveraging better engineering, such as using some industrial-rated parts, heatpipes, and moving hotter air but less volume

I'd throw down in the $6K price-point neighborhood.

Comparables:

$4800 FS S5860-48XMG-U is close but sounds like a jet engine with dual 1U screaming PSUs and 3 hot swap chassis fans, but only available in conventional top-of-rack forward facing, leading to longer, messier wire management unnecessarily.

numpad0 · 2 years ago

This isn't a desktop Ethernet switch. Lots of robotic parts like industrial cameras and fancy laser sensors use Ethernet for interfacing instead of USB or RS232C. Doing so solves cable length limitations and connection stability issues of those peripheral buses. There would be penalties and overheads of (mis?)using inter-node communication protocols like Ethernet (and TCP/IP), but those tradeoffs are completely acceptable.

What is not acceptable is full sized switches inside of a robot: they're way too bulky. You may be looking into installing a switch inside a humanoid upper arm or inside pelvis. Regular switches and hubs don't fit there.

This product solves that specific robotics packaging problem. Electrically it's a switch/hub, physically it's much smaller than that, that's the point.

globular-toast · 2 years ago

I wonder if you could do away with the switch and just daisy chain in many of those applications. It seems to be forgotten that ethernet supports this.

mike_d · 2 years ago

A Juniper EX4100 ticks all your boxes.

Adding a sound requirement is stupid and ridiculous. You're wanting to take the power supplies from 48 90W devices and put them all in one dense little box and then complaining that it needs to be cool.

If you have room for 48 PoE devices, you have room for a properly cooled and sound isoloated IDF.

userbinator · 2 years ago

For example, a TrendNet 10/100 compact switch (not a hub) goes for $7.31 including shipping on eBay and it comes with a case and a power supply

A 1G switch from Ali with a case, power supply, and the RJ45 connectors is also under $10.

gertrunde · 2 years ago

I suspect the combination of being able to dissipate 3.4kW of power, and the requested size and noise constraints may put this combination of features firmly beyond reasonable, even before considering cost.

But there is always room to hope. :)

crote · 2 years ago

A PoE-supplying switch doesn't need to dissipate that power. Assuming a power supply efficiency of 85%, supplying 3400W to downstream devices means having to dissipate 600W of heat.

Keep in mind that you'd be supplying 71W to every single downstream port. That's an insane amount of power. Something like a Cisco Catalyst 9136I Access Point only comes up to 47W, and that's assuming 16 radios, double 5Gbit uplinks, and a USB device drawing 9W.

Looks so cool! Just one question: IIUC, linear voltage regulators works by wasting voltage delta until target voltage is attained, instead of switching output current as buck converters do, so at 12V input it dissipates heat of up to (12-3.3)[V] * 0.8[A] = 6.96[W] onto the board depending on downstream current draw(of an FE switch, so I imagine would be tiny fractions of 0.8A realistically). Do board feel cool enough to touch as is?(please use back of hand/finger if unsure)

Hello, yes. Unfortunately it is hot to the touch. The board doesn’t draw 800mA, but it does get to like 60C. Max, the main designer for V2, said a heatsink is recommended. Our thermal via solution keeps it within somewhat safe temps. We wanted to keep the cost low, so we opted for the LDO. In our robot we do direct 3.3V with a buck that does 3.3 for our entire system. That’s Max’s power board.

quailfarmer · 2 years ago

Don’t be afraid to implement a basic buck converter! Something like the MPQ4572 isn’t too hard to get right (right enough for hobby projects at least).

tgtweak · 2 years ago

I would think the majority of people would be running this of of 3.7-4.2V lithium batteries or 5v USB so the step down Delta would be minimal, but yeah probably good advice to incorporate a more efficient buck step down for those running traditional 12v systems which usually operate at 14.4v.

wildzzz · 2 years ago

It may be beneficial to have an additional system power rail. Adding 5V produced by an efficient buck converter would allow for more efficient LDOs on the small boards.

Thanks - yeah 60C(140F) sounds somewhat warm, glad you're already planning for a DC-DC upstream. Feeding it 5V could make sense too(3.3V out + 1.2V dropout = 4.5V < 5V), but anyway this project feels like scratching an itch for many. Congratulations to you and your team!

LDOs are much smaller and don't produce noise like switch mode power supplies. It's true you will waste some power but that can be minimized by making the dropout voltage as small as possible.

banish-m4 · 2 years ago

bruce511 · 2 years ago

Well done.

For those of us not generally in the hardware world (and thus not 100% familiar with the terminology) could you post more pics?

Especially of the enclosure? I'm not really sure if you are just exposing headers, or if there are regular Ethernet plugs on the board?

Thank you so much! We're so happy you like it. It means a lot to us. We will be adding more pictures right now!

We're exposing 1.25mm pitch Molex Picoblade connectors to make the board as small as possible. The built-in magnetics allow it to be connected to any Ethernet device just from spicing into an RJ45 connector.

rgovostes · 2 years ago

The comparable BotBlox SwitchBlox Nano is 25.50 x 25.50 mm, albeit with two fewer ports. This is 44.90 x 42.11 mm. How do you justify the claim of being the world's smallest?

xamuil · 2 years ago

Hi, I'm Max, the lead designer of this V2 revision. You're absolutely correct! My team and I were not aware of BotBlox's 3-port switch, so a more specific description would be the world's smallest 5-port unmanaged switch. The smallest commercial alternative we found was also BotBlox's 5-port unmanaged switch [1], which we beat in both size and cost.

Once again, our mission is to create open-source, cost-effective, and accessible electronics for as many people as possible -- I think our board is much more attractive in that respect and a win in my book :)

[1] https://botblox.io/products/small-ethernet-switch

Since you have thrown ISO/IEC 8877 out the window, which is referenced by 100BASE-TX, you surely can't call it an "ethernet switch."

moffkalast · 2 years ago

> It is only 6.9 dollars

> probably for $10+shipping

You could honestly sell it for $30-40 and it would still be a pretty good deal. Meanwhile Blue Robotics be like "that'll be $175 plus $50 shipping and customs fees as a percentage of that $175 fam"

https://bluerobotics.com/store/comm-control-power/tether-int...

God, everything they sell is overpriced to the point of insanity. They could really use some proper competition.

Low volume hardware pricing always look infuriatingly high, but they also start looking hopelessly low once you've dipped toes into it and tried multiplying your spent development man-hours with McDonalds wages or tolerable unit price by expected sales volume.

I've never heard of Blue Robotics, but I doubt that $175 product ships 1k units/year, and even if they did, that's $170k revenue, or 2x entry level engineers salary worth of raw recovered cash before factoring in any expenditure whatsoever, let alone taxes and HR. It probably hardly feeds one, and that's based on an optimistic hypotheticals that they ship a thousand of that product every year.

Large scale multinational corporations ship in orders of million units. That makes it way easier to amortize non-recurring engineering and ship small products virtually at cost.

I mean sure, I understand that. But that doesn't mean I have to like it. BR are really well known to anyone dealing with ROVs or AUVs, but that's not exactly the average person.

Commercial consumer hardware R&D is mostly a fool's errand these days, since if it's something that's worth producing and sells there will be clones that work just as well available almost immediately. I'm not sure how say, Adafruit, sells anything at all to be honest, anything they make gets perfectly cloned and sold on Aliexpress for a tenth of the price. I guess going extremely niche and overpriced is one way to work around it.

marcogarces · 2 years ago

I'm super impressed and have a lot of respect for group of teenagers.

I have a question: do you have any idea what your parents did right to get you into electronics and hacking like this? I'm looking into getting my 3 kids into CS and EE, and it's something i do for a living, but i have no clue on how to make this for them. My parents never did anything except buying me all the books i asked for; I was just obsessed with knowing more cool stuff.

Thank you for sharing such a cool project with the world, your future will be very bright, keep it up!

Blammar · 2 years ago

Nice work indeed. However, was there a reason you didn't support gigabit ethernet? I haven't used 100mbit ethernet for more than a decade...

aunver · 2 years ago

Hi! I'm Altan, another member of Murex. Many of the design decisions behind the switch were driven by the requirements of our underwater robot. In our case, the communication speed was capped by the transfer speed achieved over our tether (we use galvanically isolated OFDM to inject data over our powerlines). Since size and cost were our primary goals, 100mbit was more suitable than gigabit ethernet. While it would have been cooler to have a gigabit switch, it would also increase the size and cost.

nativeit · 2 years ago

I’m not sure what your background is, but 100Mb Ethernet is still rather common in embedded devices and applications where the network protocol is primarily intended to facilitate UART serial communication. Just as a general note for context, I will defer to their more specific answer for this particular application.

Neat project!

procarch2019 · 2 years ago

Agreed. Due to the long lifecycle of manufacturing equipment we still see a lot of 100mb out there, and it’s not even embedded.

I would note that all new products seem to be gbe or better.

jmb99 · 2 years ago

As much as modern Ethernet standards are much nicer (my house is wired for and running 10Gb everywhere, with 40Gb Infiniband to a couple locations too), 100Mbps still has its place. Specifically, anything embedded, slow, and/or cheap. No reason to spend the extra money on 4 more wires and pins and trace routing if your microcontroller only sends a few packets/second.

liotier · 2 years ago

At that price point, the cost of the RJ-45 port is probably more than the cost of the 802.3 chip and I wonder if the cost of supporting that old chip on a contemporary device doesn't surpass the cost of the components for a nowadays standard 1 GB/s.

jtriangle · 2 years ago

If you're doing tethered ROV stuff, the weight of the teather is a big big deal, so adding 4 additional wires is a non starter. For the stuff that goes extremely deep, they use fiber because it's much lighter. It presents significant cost increases of course, which, you'd want to avoid if you can.

teruakohatu · 2 years ago

You can get neutrally buoyant cables:

https://bluerobotics.com/store/cables-connectors/cables/fath...

toast0 · 2 years ago

GigE needs twice the pin count. IMHO, there's not much room on the board for any more i/o. Certainly gigabit is nice, but there's plenty of applications where 100M is more than plenty.