Hacker News new | past | comments | ask | show | jobs | submit login

I totally agree with the writer, I have dedicated the last ten years to specify and implement a new single wire communication protocol for IOT and home automation applications called PJDL (Padded Jittering Data Link): https://github.com/gioblu/PJON/blob/master/src/strategies/So...

It performs much better than wireless alternatives.

16kbps over 2km, wow! How sensitive is the system to the quality of connection?

If I hide enamel coated filament just beneath my lawn is that going to be good for a one wire bus to work? Does it even need to be insulated?

It works even if you use the human body or water as a conductor, as I showcase in this demonstration (sorry for my strong italian accent): https://www.youtube.com/watch?v=GWlhKD5lz5w

This is the implementation: https://github.com/gioblu/PJON/tree/master/src/strategies/So...

This is the source code: https://github.com/gioblu/PJON/blob/master/src/strategies/So...

It is extremely rugged, it works much better than any alternative I have ever tried. Ah, it is free and open-source ;)

Looking at the interest my comment generated I decided to create a post here on HN about PJDL, please if you liked up it: https://news.ycombinator.com/item?id=23591953

The Italian accent made me think of Marconi, also your accent isnt heavy at all, just adds a little bit of color.

That is really a good compliment :)

The awesome thing with wireless IoT is that it can be set up without any additional cabling, which can be extremely painful process in most homes.

In case of wireless all you need is ESP32, relay and a power supply. And all of that together will cost less than 10$.

Can you easily (cheaply) use the already existing power cables for PJDL? I know there are network repeaters that use power cables to transfer data, but I have no idea how much it would cost in IoT scenario. Do you have some examples?

Yes many users have squatted old phone wiring, here in italy in most houses it is embedded in walls, and it is present in most rooms. Being unused and obsolete it can be used for home automation with PJON :)

As a software person who doesn't know much about this sort of thing: how does this work electrically? Presumably there's no current flowing as it's an open circuit? Is it akin to a voltmeter using the ground as a point of reference? Why don't other wire-based protocols use the single-wire approach?

Does it have anything in common with 'single-wire earth return', in power-distribution?

The protocol is really simple +5v is 1, 0v is 0. The circuit is just a single conductor and a common ground pin. If you connect a LED between the bus and ground you can visually see packets in form of light pulses.

Here's why it's a good idea to insulate underground cables or use optical fiber: https://youtu.be/Ev0PL892zSE?t=357 (TLDW: the salient point is at 7:20: https://youtu.be/Ev0PL892zSE?t=440).

Though, I don't know if insulation helps in the case of lightning. Apparently with Ethernet, special grounding thingies help.

Yes, in production it is suggested to use current-limiting resistors, pull-down resistors, a fuse, a zener diode or a TVS or a varistor. Using all the suggested protective circuitry in the worst case the fuse should be the only component to fry in case of direct lightning strike.

Lightning crosses several hundred meters of air at the very minimum- what makes you think it won't arc over a few millimeters more, if that's the path of least impedance?

In general even the most rugged lightning/surge protection only decrease the likelihood of protected equipment being vaporized.

I agree that in some cases there is nothing to do and damage will be done by the strike and there could be no protection able to prevent it, specially if the equipment is directly hit. I would have corrected my previous statement but it cannot be edited.

have you worked with VDSL modems and lines?

it can be a nightmare.

Looks cool. Why single wire and not a simple twisted pair? Are you using a voltage relative to earth for your logic states? Just not sure how it could work otherwise.

A twisted pair seems nice to me because you can use differential signaling and not have to ground your devices e.g. 2 wire RS485.

Yes the voltage is relative to ground for the logic state, the differential signaling requires a source of negative voltage and a more complex front-end, being relative to ground you just need a digital IO operating at 5v or 3.3v and a ground pin, no additional hardware (although current-limiting and pull-down resistors are suggested), as a result it can be fully and easily bit-banged. The twisted pair (where one wire is the bus and the other the ground) is one of the suggested approaches that helps to reduce the interference induced on the wire.

Radio systems have an antenna that radiate energy into the atmosphere. Other antennas resonate in harmony.

What if you just connect the antenna wires of all the devices together?

That's what a single wire protocol does.

I'm not really knowledgeable so excuse me if I have a misunderstanding as I try to reason about this from a different perspective.

When you have an object with static electricity and put it in contact with a different object, there will be a transient current, even if the circuit is not closed. The objects basically work as poor-man's capacitors.

Even though the name is "static electricity", when the objects come into contact, it's actually more dynamic than normal, because there is no current between two objects of fixed and different voltage. The more current that flows, the lesser the voltage difference becomes, in an exponential fashion.

This kind of single wire protocol operates solely based on these kind of transient currents. Because the frequency is so high, very little current flows during one period of the waveform, so the receiver will maintain constant potential, as if it was grounded.

That it isn't actually grounded means the signal becomes high-pass filtered. In particular, the DC-component must be completely blocked as it would lead to charge buildup with nowhere to go.

Applications are open for YC Winter 2023

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact