- Joined
- Jan 28, 2018
If you go back in time enough the power was actually supplied by lead batteries to assure there was no humming on the line. Not so necessary in more modern networks. The advantage of such a self-reliant network is that even if power fails because of catastrophe but the network isn't damaged, you can power it through other sources and make sure the phones work. The network as it exists now in most countries doesn't have that feature built-in anymore.
I only skipped through it. Just whacking a 7805 on the line like this wouldn't work, for starters it isn't rated for that kind of voltage and it wouldn't create the "hook off" event safely enough to make sure the voltage drops into a safe area for the regulator reliably enough through resistance. Even if we assume we get to the part were we get the line pulled down immediately to a safe voltage (that could happen, but I would not bet on it) for the 7805 directly and to the point upstream thinks the hook is off, (but still doesn't disconnect automatically because it senses a fault condition) I don't even have to do the math (as I don't have the exact numbers anyways) but alright, let's just assume this somehow magically works and the usb charging IC doesn't even mind the 7805 is oscillating because whoever made the video didn't even bother to read a 7805 datasheet to do the bare minimum, you'd still not get the absolute minimum of 500 mA according to usb spec to even start the charging, guranteed. Frankly I think 500mA/5V isn't even enough for many modern mobile devices to effectively charge. (It actually might detect there's a few mA, but they'd probably not cover the "expenses" of the phone running) I think the most likely thing to happen in this scenario is the 7805 dying as soon as it closes the circuit, probably letting the full line voltage through and toasting the usb charging IC in the phone which usually at least should die quick enough to stop worse things from happening with the battery. I'm sorry that video is just absolute clickbait and a bad idea, don't do this.
If I wanted to do it old-school in a time where all this was relevant I'd take a variable regulator (e.g. TL-783) variable only alone for the fact that many of them can take voltages of over 100V and are relatively easy to get. I'd then adjust with a variable resistor to whatever value I measure on the line and throw a few capacitors in to make it nice and smooth. (Disclaimer: This is probably illegal wherever you live - don't do this - I also left out an important part for this to work reliably and deal with the whole hook off/ringing business, need a few more parts for that) If I'd do it nowadays I'd take a more modern switching mode regulator, because linear regulators are really inefficient and I'd want to make sure to get the most of what little is there. I wasn't saying it's entirely impossible to steal some mW from the phone line, it certainly is, it just is really, really pointless for the amount of juice you get, especially in the relation of the size of the crime. You can put some solar panels on your roof or buy one of these camping solar things and put it outside. More energy, perfectly legal. (If you buy a fancy camping one it might even be enough to operate a small ARM SBC most of the sunny times of year if you live in a sunny area, electricity from the socket would be cheaper though if you factor in cost of equipment)
If you're really gung ho about sticking it to the man and stealing electricity, there are USB outlets nowdays in many public places, you could go there with a powerbank and try to act inconspicuous. You'd have a hard time to get whatever the powerbank costed back tho. No such thing as a free meal. My uncle (may he RIP) drilled a hole behind his kitchen cabinet which lead to the stairwell of his apartment building and he wired his electricity to the power lines supplying the lamps in the stairwell. Nobody ever noticed, and electricity wasn't that expensive then anyways. Now that's effective power stealing. (I'd imagine in most places they'd notice nowadays)
I used to use my A2000 and a 7-port (?) serial card to run a BBS nobody ever called for a hot second in a slow summer. It was a brainfart of an idea and more expensive than I like to admit nowadays. I guess nowadays you'd automatically end up on 10000 lists for running your terroristic board with gamer words and the occasional gay joke. The nicest thing about the online stuff back then was that the powers-that-be didn't understand it and also didn't care. That gave you tons of freedom we'll never get back. Also less random schizos wandering in on their android phones and trying to warn you abrout hebrew jew lizards digitally tracking your cornflakes.
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