Wiring genius: 48v power + data CAN bus

You know how cars have huge wiring harnesses?

That's because each component needs its own set of wires, connected to the central ECUs, in order to function.

Every speaker, every switch, every sensor, every actuator, every button.

Tesla threw out that entire system for Cybertruck.

Instead, they're running gigabit ethernet cabling with a 48v power + data CAN bus to every component— all on the same cable.

Instead of running one wiring harness to the driver door speaker, and another to the driver's door window motor, they can daisy-chain them together on the same self-contained cable interface. Your computer could connect to your door handle using the *same* wire that's already been through your speaker, window, ambient lights, and steering wheel.

Each of those devices/components listen to the continuous stream of data for a command relevant to its operation.

By doing this,Tesla was able to reduce the total wiring in the Cybertruck by 77%, using 1/2 the copper.




cybertruckguy

Aptera are doing the same thing.

and still the price went up so much.

Marrero said:

and still the price went up so much.

Click to expand...

But not as much as it would have if the wiring was traditional.

But

Power and data signals travel on different circuits

Or is someone seriously suggesting eg the speakers are operated only by data packers

this seems misleading or confused

Yep.

The daisy chained bus architecture was actually more important at reducing wiring than the 48V upgrade.

This has been happening for a while in cars as microcontroller costs fall, it becomes more cost effective to distribute controllers in the vehicle rather than long cables, unlike the analog days.

There's still 12V on the vehicle, all the CPU/GPU, displays etc will need it, plus the USB-C PD outlets etc.

Can I get a reference for how this works?
I had to wire seperate gigabit cable to everything in my house - one for tv, one for every camera, repeater, computer needing wired connection..
I have at least 8 wires going, some are plugged through a switch because the router can only take 4 cables.

I would very much like to do chained connection in next cabling I need to run.

The reduced cabling was enabled by using 48v to reduce the needed cable thickness.
The can bus stuff was already done with the Model 3 & Y, and even partially the Model S/X.

Jason Cammisa does an excellent job describing the Tesla's 48 volt architecture at 10:14 in this Youtube review.

cvalue13 said:

But

Power and data signals travel on different circuits

Or is someone seriously suggesting eg the speakers are operated only by data packers

this seems misleading or confused

Click to expand...

It remains to be seen if audio is digital or analog (analogue?) but digital transmission would present timing issues; a few ms difference between speakers would cause some odd reverb effects. It would also mean that each speaker had a separate amp, which seems unlikely.

cvalue13 said:

But

Power and data signals travel on different circuits

Or is someone seriously suggesting eg the speakers are operated only by data packers

this seems misleading or confused

Click to expand...

48v power is supplied over the ethernet cable, apparently. For the 802.3bt passive power standard, up to 100 watts is available. That may be enough for the majority of the powered devices in the network, or perhaps Tesla is using a more capable design (heavier gauge conductors, for example), a more capable standard that I'm not aware of, or for the power hungry devices like the steering rack motors, separate power cables as you stated.

Speakers could easily be handled by sending the audio as digital data and including a DAC and power amp on each speaker. That type of distributed audio system design could revolutionize mobile audio systems; with the proper audio signal processing and speaker placement, every person in the vehicle would hear exactly the same audio soundstage, beamed directly at their head, with perfect multi-channel balance. That advance may already be underway. I'll have to check...

***** edit*****

I checked. Of course, that audio idea is being worked on already. You can add seating position specific active noise reduction to the list... Here's just one reference: https://toshiba.semicon-storage.com.../innovationcentre/whitepapers/TCM0562_ENG.pdf

Carmageddon said:

Can I get a reference for how this works?
I had to wire seperate gigabit cable to everything in my house - one for tv, one for every camera, repeater, computer needing wired connection..
I have at least 8 wires going, some are plugged through a switch because the router can only take 4 cables.

I would very much like to do chained connection in next cabling I need to run.

Click to expand...

A mesh wifi system solved that problem for me.

But if you want to keep everything hardwired, look up "Daisy chain ethernet" to see how it can be done and why you probably don't want to do it for a personal residence. It requires an ethernet switch at every daisy chain point. Here is one article: https://www.techrepublic.com/article/only-novices-daisy-chain-switches/

I would assume one downside of the daisy chain wiring is, that if you have a damaged wire, now everything downstream stops working not just one item.

cvalue13 said:

But

Power and data signals travel on different circuits

Or is someone seriously suggesting eg the speakers are operated only by data packers

this seems misleading or confused

Click to expand...

They are calling it 48V POE but it has nothing to do with the household/office/industrial Ethernet 802.3 POE standard. Standard POE can only do up to 100W max, which isn't enough to do much at all in a vehicle, except run sensors or window winder motors etc.

It could never handle the 5hp required for the SbW for example, or the AC compressor, cooling system etc.

First up it's 4 core round cable based and not 8 core, and it uses a "connectorless" connection system that just terminates a precisely cut cable end directly into a node without a plug. The cable is also considerably thicker than CAT5/6 LAN cable, so it can run higher power devices.

It's technically feasible that nodes can be added to an existing cable as well, by simply clamping a node over the cable, and that node then pierces the cable insulation to make contact with the 4 cores, establishing both power and data connectivity.

The way POE handles data and power on the same cable, is that power is delivered at a steady 48V DC between two pairs of cables each, and a data signal is modulated at a high frequency, like a radio broadcast down the same cable.

This is also how Ethernet over power adapters work, where you can use existing household wiring to connect LAN devices within the house.

The system will also likely include node based electronic fuses for loads and short protection, potentially PWM and DC converters to run small motors or LEDS etc. It will also be ring powered and use a CAN like bus, where each node on the cable ring bus, is connected in either direction along the ring. This means that even if you cut the ring cable in one spot on the ring, the nodes will still function and connect the other way through the cable ring for redundancy.

The critical thing to get it to work in a vehicle is noise immunity. In normal ICE vehicle, high voltage ignition systems don't play nice with data signals, but in EVs there are no spark ignition sources. But there are high powered fast switching inverters that like producing harmonics all over the spectrum without sufficient filtering. So it's critical to have a high bit rate connection with error correction, along with usual data integrity protection algorithms.

Overall it more closely resembles a nervous system, just without all of the self healing parts.

CyberGus said:

It remains to be seen if audio is digital or analog (analogue?) but digital transmission would present timing issues; a few ms difference between speakers would cause some odd reverb effects. It would also mean that each speaker had a separate amp, which seems unlikely.

Click to expand...

Nowadays DAC chips with Class D amps are a dime a dozen, and most come with I2S or SPI bus and even with ethernet stacks.

Timing is rarely an issue with high bandwidth digital multi channel systems capable of wave forming techniques, like the Starlink phased array, using DSP processing to create directional sound "beams", that can be focused in 3D space to each listener.

Have a look at the Yamaha YSP soundbar tange, they have been around for over a decade and run 42 speakers just like that to create 3D sound from one box, each speaker driven by its own amp, and perfectly synced to beam form. I have one.

Apparently the sphere in Las Vegas uses the same technology for their audio. Interesting stuff.