Rendered at 15:32:25 GMT+0000 (Coordinated Universal Time) with Cloudflare Workers.
ralferoo 3 hours ago [-]
Accepting 5V over the RJ-11 jack seems asking for trouble. Someone is going to plug it into a regular phone socket at some point, so it needs to be capable of surviving at least 60VAC. Even if a secondary pair is used, there are so many different wiring standards in use, it'll end up plugged into something live sooner or later.
alnwlsn 22 seconds ago [-]
Luckily telephone lines are very current limited. You'd be hard pressed to draw more than 100mA even with a dead short at ring voltages. One zener diode might be all you need.
Also not the most unusual thing I've seen over a RJ11, which includes keyboards, RS-232, other random digital IO and full USB with data. But these are normally on items that are not phones.
mikeweiss 3 hours ago [-]
Dunno about you but I don't know anyone with live RJ-11 jacks in their house anymore.
ssl-3 1 hours ago [-]
It's been a very long time since I had a cable modem that didn't have a pair of 4P4C (aka RJ11 or POTS) jacks on the back. These exist to make available the VOIP service that I haven't wanted for decades.
Others using this same enormous, American ISP probably have similarly-equipped gear.
But I must admit that it has also been a very long time since I connected anything there. I don't know if they supply 48v talk battery or not when the modem has a data-only configuration.
aftbit 23 minutes ago [-]
I've got them, powered by an Adit 600 in my basement.
ge96 15 minutes ago [-]
That would be funny you're at a club with this phone and doing phone calls
walrus01 4 hours ago [-]
For the 21700 cell if you want to do this without spending a lot on batteries, but also be sure that any misconfigured hardware can't drain the battery below a damage threshold, use a button top protected 21700 cell. Here's a good 'house brand' one that is popular with 21700 flashlights.
Mmmmmmmmmmhhh. Maybe better to damage
A battery than to have a drone fall out of the sky? Also most protected cells have modest current capabilities, and might not be enough for many drone applications.
By its nature, MUAVs tend to push batteries to their limits and lifecycles tend to be limited. A battery that does mission X must have a maximum weight and a minimum capacity, and a minimum current spec. If you increase the life cycles, you decrease the maximum performance (range, payload, etc).
When you get into bigger drones, more modest restrictions on mission capability give acceptable tradeoffs, but for MUAVs short cycle life is often seen as an acceptable cost.
Frequently , after a hundred (or often much less) cycles in a MUAV a battery is retired from stressful missions due to significant drops in capability. It’s still fine for other uses, but at 90% it’s no longer sufficient for frontier MUAV applications.
The best choice to keep drones from falling out of the sky is to make sure that your auto land is set to a reasonable battery level (calibration by height if you will be at altitude) and use cell cutoffs at or below the minimum safe voltage if at all. (They are usually set to a few tenths of a volt above the minimum safe, often as much as 500mV.) The final battery voltage should be managed manually and batteries tested if over-discharged.
At least, that’s what prevents the most hardware from falling out of the sky onto people’s heads, sometimes bursting into flame on impact. Usually that is seen as the least desirable outcomes of a battery stress situation.
walrus01 3 hours ago [-]
So I was referring specifically to this phone hardware project and to flashlights, which don't fly... But my thoughts on drones are also that it's very different if you're building consumer class things that are meant to be re-used or what's going on in ukraine right now. They're using high amp rate cylidrical 18650 and 21700 cells in 6S2P and 6S3P packs for one way trip munition drones where you don't particularly care if you damage the li ion cells for any future re-use. In which case in the last few minutes of flight you can abuse the hell out of them with high amperage draw down to 2.5V (but beware of extreme voltage sag at the bottom end) and never have to worry.
If we're talking about something that's designed to be re-used then a totally different set of design considerations, as you outline above, become applicable.
> Frequently , after a hundred (or often much less) cycles in a MUAV a battery is retired from stressful missions
Are you talking about lipo pouch cells or li-ion cylindrical? Because if we're talking about state of the art high amp draw rated li ion cylindrical cells, 100 cycles on something that isn't heavily abused for heat and doesn't go below 15% state of charge should not significantly affect its lifespan. But if the batteries are being abused or every last bit of margin on range/payload is needed that it calls for almost "factory fresh" cells, or there's just absurd amounts of DoD money to throw at buying new battery packs, sure, I guess.
K0balt 2 hours ago [-]
If you’re getting into bigger (kg+) drones, it starts to make sense to shoot for 100cycle+ (and for 10kg+, 1000 cycle-ish) lifespans. The economics and the physics work out. But for very tiny systems like the single cell drone featured, the equation starts to favor squeezing every last drop of energy reasonably possible, which means that you can easily get caught out downwind or “stayed to get a few too many pictures” and end up hitting the safety walls. (Partly because the risk of doing so is proportional to the size)
c22 3 minutes ago [-]
> ...like the single cell drone featured...
Featured where?
ssl-3 1 hours ago [-]
What are the chances of this telephone falling out of the sky due to battery failure?
aftbit 22 minutes ago [-]
Who mentioned drones? This is for a phone.
shrx 3 hours ago [-]
We have a similarly converted rotary phone at my local astronomy club's observatory, used to receive visitors. It's driven by an arduino if I remember correctly. The main issue is that the sound quality of its built-in speaker is quite poor, especially compared to modern cell phone speakers we're used to nowadays, with a narrow frequency window and frequent echoes.
alnwlsn 37 minutes ago [-]
In contrast, I've been messing around with some old analog phones and VOIP stuff recently, and I've been blown away with how good the quality is over what I was expecting. The audio bandwidth is low yes (it's G.711u, so 8 KHz), but the actual quality is great, with no hyper-compression artifacts or over-applied background noise filters. And yes this is on the original 60's carbon microphones.
The regular phone calls I normally make on my cell still all sound like they are underwater for some reason, except for those rare times when the better connection is actually working.
waltbosz 2 hours ago [-]
I've seen projects that swap out the rotary phone speaker with a speaker from a pair of on-ear headphones.
Interesting. I remember voice clarity being exceptional on old handsets and being really subpar on gsm and later. Only now we FaceTime voice and discord the quality seems to be coming back.
How can that be if the speakers in phones ubiquitously were so bad?
Someone 58 minutes ago [-]
Could be that it wasn’t bad but has gotten bad because of aging of the speaker, capacitors, resistors, etc.
bux93 2 hours ago [-]
Cool! But who remembers phone numbers anymore? Maybe a small screen that you can navigate by dialling 1 (down), 5 (up) and 0 (select) would be a cool add-on (after dialling 0 or 411 to reach the operator perhaps).
ssl-3 2 hours ago [-]
The next move is to go further back in user interfaces: To place a call, pick up the phone and dial 0 or turn the crank to ring the operator.
Have a bot do the rest, exactly like a telephone operator.
eggfriedrice 7 hours ago [-]
Lovely job, I like the "here's where I've got to so far" style. This gives people enough to work from and make a hand-wired version while he's waiting for boards to come back. Even if he runs out of time to do anything it's leaving a working design and firmware for folk to start from.
It's definitely too easy to put off publishing until it's "properly" done and then it never happens.
hi_hi 7 hours ago [-]
When I finally agree to cave in and buy a phone for my soon-to-be teenager, little does she know this is the phone I have in mind…
throawayonthe 7 hours ago [-]
i wouldn't want my child making unencrypted calls :p
walrus01 4 hours ago [-]
It's no more or less encrypted than any cellular phone making a call across your local 3GPP-whatever standard network.
boxed 7 hours ago [-]
Doesn't this project go straight into modern standard mobile phone systems? It'll be encrypted then.
fc417fc802 6 hours ago [-]
I think he might have been calling into question the wisdom of using the standard telephone network to directly place voice calls. Technically it's encrypted but your privacy is anything but guaranteed.
There's a lot of hardware out there that does 95% of what OP's does, though you'll pay a pretty penny for it (e.g. https://www.peplink.com/products/cellular-modems-adapters/po... ) though ther's been a flood of them from noname sellers on Aliexpress and eBay under the banner of "LTE Landline Converters"
Trace88 11 hours ago [-]
Love seeing old tech brought back to life like this. The tactile experience of dialing is just something else.
This project uses the same AG1171 SLIC module; it's just not enough by itself and still requires a microcontroller (or at least non trivial logic) even before you get to processing the audio streams.
Also not the most unusual thing I've seen over a RJ11, which includes keyboards, RS-232, other random digital IO and full USB with data. But these are normally on items that are not phones.
Others using this same enormous, American ISP probably have similarly-equipped gear.
But I must admit that it has also been a very long time since I connected anything there. I don't know if they supply 48v talk battery or not when the modem has a data-only configuration.
https://liionwholesale.com/collections/batteries/products/pr...
By its nature, MUAVs tend to push batteries to their limits and lifecycles tend to be limited. A battery that does mission X must have a maximum weight and a minimum capacity, and a minimum current spec. If you increase the life cycles, you decrease the maximum performance (range, payload, etc).
When you get into bigger drones, more modest restrictions on mission capability give acceptable tradeoffs, but for MUAVs short cycle life is often seen as an acceptable cost.
Frequently , after a hundred (or often much less) cycles in a MUAV a battery is retired from stressful missions due to significant drops in capability. It’s still fine for other uses, but at 90% it’s no longer sufficient for frontier MUAV applications.
The best choice to keep drones from falling out of the sky is to make sure that your auto land is set to a reasonable battery level (calibration by height if you will be at altitude) and use cell cutoffs at or below the minimum safe voltage if at all. (They are usually set to a few tenths of a volt above the minimum safe, often as much as 500mV.) The final battery voltage should be managed manually and batteries tested if over-discharged.
At least, that’s what prevents the most hardware from falling out of the sky onto people’s heads, sometimes bursting into flame on impact. Usually that is seen as the least desirable outcomes of a battery stress situation.
If we're talking about something that's designed to be re-used then a totally different set of design considerations, as you outline above, become applicable.
> Frequently , after a hundred (or often much less) cycles in a MUAV a battery is retired from stressful missions
Are you talking about lipo pouch cells or li-ion cylindrical? Because if we're talking about state of the art high amp draw rated li ion cylindrical cells, 100 cycles on something that isn't heavily abused for heat and doesn't go below 15% state of charge should not significantly affect its lifespan. But if the batteries are being abused or every last bit of margin on range/payload is needed that it calls for almost "factory fresh" cells, or there's just absurd amounts of DoD money to throw at buying new battery packs, sure, I guess.
Featured where?
The regular phone calls I normally make on my cell still all sound like they are underwater for some reason, except for those rare times when the better connection is actually working.
The Secret Life of Machines TV show has a fun demo of how the speakers in old telephones produce sound https://youtu.be/MCgCSMq5Xpo?si=CT5aOGttBpPk9tEM&t=458
How can that be if the speakers in phones ubiquitously were so bad?
Have a bot do the rest, exactly like a telephone operator.
It's definitely too easy to put off publishing until it's "properly" done and then it never happens.
https://youtu.be/nibV_idJjlg
https://www.ebay.com.au/itm/305557776577