Step 3: Construct a Simple Voltage Regulator Circuit

We know that the phone needs 5 volts in order to charge. But we don't know how much current it draws or it's equivalent load resistance. So we can't charge the cellphone directly from the phone line. We need to use a voltage regulator to bring the output of the phone line down to 5 volts and keep it there. A LM7805 5 volt regulator should work fine. 

To make this simple phone line adapter you will need the phone cord that we have been working with, the 5V voltage regulator and a USB connector cable with a female end. Just connect the red wire from the phone line to the first lead on the regulator and connect the green wire from the phone line to the second lead. Then connect the black wire from the USB cable to the second lead on the regulator and connect the red wire from the USB cable to the third lead on the regulator. If you can't solder the wires together (because the power is out), you can just wrap the wires around each lead. If you do this, you should bend the leads of the regulator away from each other. This will help you avoid accidentally crossing the wires.

This simple regulator circuit is able to safely convert the base phone signal into something that can be used to charge your phone. However, many voltage regulators are not able to handle the AC signal that they would receive if the phone rang. So if you are worried that you might receive a call while your regulator is hooked up to the phone line , then you may wish to add a diode between the red wire from the phone line and the first pin on the voltage regulator. This will protect your circuit from problems that may be caused by reverse polarity.

1) If the phone line is powered, you can make the emergency call on it.<br> &nbsp;&nbsp;&nbsp;&nbsp; ( As several other people have said.)<br> <br> 2) This is dangerous. Fifty volts is where volts have already started getting dangerous.<br> <br> 3) I am an electronic technician, and I would never do this.<br> <br> 4) You can keep a spare charged phone battery to use when the first is flat. (As I do.)<br> <br> 5) You can have a second phone charger in my car. (As I do.)<br> <br> 6) You can have a USB cable to charge your phone from your laptop. (As I do.)<br> <br> 7) What happens if your phone hack prevents some of your neighbours from making emergency calls on their landlines ?&nbsp;&nbsp;&nbsp; Do you want to be responsible for someone's death, just because you are too mean and selfish to take reasonable sensible LEGAL precautions for power cuts like everyone else does ?<br> <br> 8) DO NOT encourage people to do dangerous illegal things.&nbsp;&nbsp; If they do, and they suffer for it, you share the responsibility.&nbsp;&nbsp; (But I'm sure you will deny everything.)
<p>i too am a electronic tech...... and as my rule of thumb, 30 volts or above is dangerous</p>
<p>Electric fences run thousands of volts. Static electric shocks can be around 20,000 volts. Stun guns can produce upwards of 100,000 volts. It's not the voltage that kills you, it's the amperage. The voltage just determines whether or not the shock can make it through your skin. You would be vary hard pressed to electrocute yourself on a POTS line, absent some extraordinary occurrence like lightening strike. </p>
<p>I agree. A lot of so called &quot;electronic techs&quot; on here that don't know much. The voltage is far less important then the amperage. </p>
<p> You disply ignorance your self. The available current and the available current are of equal importance. Lethal current can't flow unless the voltage is high enough to overcome the resistance. There are two excellent videos on YouTube that illustrate how inane and dangerous the &quot;its the amps that kill ,not the voltage&quot; chant is. I suggest people look for them. I would list them here, but my bookmarks crashed and I yet to have to restore them all.</p>
<p>Do not trust the great &quot;University of Youtube&quot;. Careful your ignorance is showing.</p>
<p>Hold one wire in each hand and have someone call your line. </p><p>I dare you. Post back and let us know how it went.</p><p>You <strong><em>probably</em></strong> won't die, but I guarantee that you <strong>will</strong> be really glad there is a pause between rings so you can let go of the wires.</p>
<p>You can let go of the wires either way. You aren't sticking your foot on the third rail of a subway or grabbing the 240 in your breaker box. What is it about this thread that so fascinates people that have obviously never worked on a telephone line? The ringing voltage is irritating at most. The feeling is comparable to one of those hand buzzers people used for practical jokes in the eighties. If it was lethal there wouldn't be any telco techs alive today. </p>
<p>&quot;</p><p>7) What happens if your phone hack prevents some of your neighbours from<br> making emergency calls on their landlines ? Do you want to be <br>responsible for someone's death, just because you are too mean and <br>selfish to take reasonable sensible LEGAL precautions for power cuts <br>like everyone else does ?&quot;</p><p>If it really worked this way a dead short which is not all that uncommon occurrence, on an individual line would knock out other lines since the short draws 100% of available power to the shorted line. Fortunately, it doesn't work this way. The only possible problem would be on a &quot;party&quot; line and I don't know anyone who has had one of those since the early eighties. </p>
<p>As a friend of mine just pointed out - when the power is out, the phone company lines are running on batteries. So this suggestion is to use someone else's batteries because you were too cheap or too stupid to buy your own in advance. Plus, you are then draining the phone company's back-up batteries. Which means, yes it can effect your neighbor's ability to make an emergency call.</p>
I kept a land line on the theory that the phone co. batteries would still be working in an emergency. When when the big hurricaine came and knocked out the power for days they were down too. Get a generator, preferably one that runs on natural gas if you have service.
<p>The reason I retain the land line it's the cell phone circuits that will be overloaded first. I'm sure the cellular system has back up power as well.</p>
I liked what you said thus i just paraphrased you.
Oh stop it. <br>If I do this, which I will, it's not going to make a damn difference to my neighbors.
<p>Yes, in a way it is. You are tying up a &quot;dialing unit&quot; and a phone line. There are only a limited number of these valuable resources - there is not one for ever line.</p><p>In an emergency, you may be preventing someone from making an emergency call, or contacting loved ones.</p>
<p>2) No, 48V telephone battery is not dangerous. Up to 60VDC is rated as Safety Extra Low Voltage (SELV) and is safe to touch. See UL60950 for definition.</p><p>3) Your choice.</p><p>7) This is no different to going Off Hook with a regular phone. So you won't block anyone else's calls. If you don't make a call after 5 mins or so the phone company cuts off the power anyway.</p><p>8) It's not dangerous but it is illegal to use telephone company power for any purpose other than making a call. See Code of Federal Regulations CFR Title 47 Part 68.</p>
It is not dangerous. There is 48-52 volts, but very little amps.
I just bought 80 surplus car batteries (yep--they're the 12VDC kind)--they're down in my basement and I've connected them in series right beside the point of demarcation for the phone line. In about 10 years we can take the clothes dryer offline for one load--and Ma Bell will be footing the bill. Life is Sweet!
<p>So you now have a 960 Volt battery, capable of about maybe 200 Amps, in your basement ? I guarantee this will explosively destroy any domestic appliance you connect it to ! You are sitting on a bomb !</p><p>Please tell me I misunderstood you !</p>
<p>Do you know what &quot;in series&quot; means?</p>
<p>Hahaha no way!!! 80!?! </p><p>That would be AWESOME if you really did this. But 80 batteries!?!</p>
<p>Firstly, I'm inclined to agree with many of the <strong>negative </strong>comments being made as one cannot guarantee exactly what voltage is coming down the line at any given time (e.g., an incoming ring signal), and that an average Voltage Regulator is not properly equipped to deal with higher voltages.</p><p>Secondly, while such a hack may <em>work </em>in an emergency, you may find that your cell phone is still useless because the power outage could have affected your local towers and you won't have a signal anyway.</p><p>I agree that if the landline is functional, have a standby &quot;emergency&quot; handset connected. In modern times, even if the line is officially &quot;disconnected&quot; it's still able to access &quot;999&quot;, &quot;000&quot;, &quot;911&quot;, &quot;0118 999 881 999 119 7253++&quot; or whatever the emergency number is in your country.</p><p>++ https://www.youtube.com/watch?v=HWc3WY3fuZU</p>
power outages effect less then 2% of cell phones towers a year<br>they run off generators <br>mr
<p>Living in a country where the idea of &quot;sharing&quot; towers is totally anti-corporate and having had zero service for a contiuous period exceeding 48 hours, I would still recommend having a cheap handset connected to the landline socket for emergency situations.</p>
<p>Maybe, but maybe you didn't know that a cell tower cannot handle more than 7 DS0 communication line simultaneous. So when everyone call, they drop the extra. Soo, basically, once 7 people are one the line, you'll get a busy signal from that cell tower.</p>
<p> The lead photo shows a cell phone being charged. Depending on the emergency public safety agencies will get priority use of the cell phone system. When the genera public gets access it will be for time slots that could be short, plan ahead accordingly. Could be that POTS will be the system you will be able to use to get through to who it is you need to speak to</p>
<p>This is illigal in most state accros the US and Canada. It is covered by the Computer Act.</p>
<p>While that may be true in some States, I don't care. Say the power goes out and all my backups failed for whatever reason (including me not keeping batteries charged or new batteries that discharged due to sitting a long time) and a family member needs help and doing this hack gets me help, to save them, well screw the law. I'll deal with that when it happens. I seriously doubt you would be charged, and if so, then so be it.</p><p>Are you telling me you would let a family member or for that matter, ANY human die, because it is illegal where you live? If so, I guess you will have to answer to a higher power, if you believe in such things. I use simple common sense on these things, by weighing cost/reward. Here the cost is probably zero, to a fine of some sort. The reward is saving a life. Hmmm, which do I choose? I know my answer! What's your answer Sarah? </p><p>Have a wonderful day Sarah.</p>
<p>Assuming the same problem that took out the power didn't take out the telco lines that run on the same poles, probably all you are going to do is fry your phone the first time a call rings in. It's a lot less tolerant of that AC ringing voltage than you are. That's on top of all the other issues mentioned. If you can manage to have on hand what you need to do this so it actually works you can have on hand the right charging equipment for your phone if the power goes out. A car charger is obvious if you have a car. A 12 volt battery and small inverter is pretty easy too. If all that fails, maintain landline service and plug an actual landline phone into the telephone line since that's what it's supposed to work with in the first place. Basically if you are desperately searching for the stuff you need to do this hack without destroying your phone in the process, it's because you are already totally unprepared. </p>
<p>Even in most rural areas the phone lines are underground, and are well protected. Except for the occasional freack lighting strike that will find a path to under grounf cables In the event if the switching equipment see this as an off hook condition it will place a higher voltage dial tone signal on the line, no need to wait for someone to call that number</p>
OK, I got your point, but if it's help you need, don't you think a simple wired telephone should be able to get the job done.<br><br>Don't get me wrong here, I knew a thing or two about survival and preparedness and one thing I know for sure is that if power fail because of an earthquake or even a high atmosphere nuke detonation, the power coming out of those line would be out too since the machine supplying it would probably get destroyed.<br><br>Don't believe that Los Angeles movie, in that scenario, most building are on the verge of collapsing, soo the wire are mostly cut.
<p>Corded phones with backlights, speaker capabilities and other functions are powered by the phone line so I think some of your admonishments are specious.</p>
<p>Most corded phones without separate power supply are pretty bare bones. Most of the corded phones that have those things have a separate power supply just like an answering machine or a cordless phone base unit. Especially those with speaker phone. </p>
<p>I would suggest a change from &quot;Most&quot; to &quot;Many&quot; phones need external supplies but I had to look no further than our line-powered backup corded phone (we have little cellular coverage and frequent land-line outages) a Northwestern Bell 20600 for a speakerphone, and there are a number offered online, some with backlighted displays &amp; caller Id requiring AAs but no AC. </p><p>I have never bothered to measure current drawn for speakerphone usage but drawing 0.5 watts for that would provide adequate power for the small speaker used without causing problems for the service provider.</p>
<p>Americans are not very intelligent and their spelling is really poor!</p>
<p>This trick is as old as the hills, and has always presented an danger to all those that have tried it.</p><p>Is it worth your health &amp; bank account, when you get caught?</p><p>good luck</p>
This is a neat hack and hacks are exactly that - often a bit shady, reusing things in ways they shouldn't be used. I hadn't thought of this but it may serve me well in te zombie apocalypse, or after Isis invades, and we need emergency power and ethics and safety are out the window. I'm in favor of sharing ideas, period!
<p>It may have changed over the years but the 50V (~48V from batteries) was fused at 75 mA so going beyond that would once cause a fuse to pop in the switching facility servicing your phone line necessitating a call to the service provider to restore the circuit.</p>
One thing.. if you need to charge a cell phone for an &quot;emergency call&quot;, and you are going to use a phone line that is in service to charge your phone, shouldnt you just use the landline instead of waiting the 12 hours of charging to get your smartphone on?
<p>I'm surprised nobody else has noticed, but the &quot;phone&quot; pictured above in this instructable is NOT a landline phone-- it's a Cisco IP phone, which is a VOIP (voice over IP) phone. I mention this for clarity, since if you have one of these, if your power goes out, so does your service. In fact, if your internet connection goes down (even if the power is still on), you also lose your service. And since VOIP is usually powered via POE (power over Ethernet), it's a completely different spec than described for this instructable.</p><p>I personally wouldn't try this for a large number of reasons, as there are many more (and safer) ways to charge your phone during a power outage.</p>
<p>I'm surprised nobody else has noticed, but the &quot;phone&quot; pictured above in this instructable is NOT a landline phone-- it's a Cisco IP phone, which is a VOIP (voice over IP) phone. I mention this for clarity, since if you have one of these, if your power goes out, so does your service. In fact, if your internet connection goes down (even if the power is still on), you also lose your service. And since VOIP is usually powered via POE (power over Ethernet), it's a completely different spec than described for this instructable.</p><p>I personally wouldn't try this for a large number of reasons, as there are many more (and safer) ways to charge your phone during a power outage.</p>
<p>If you have a phone line, why not plug a landline into it?</p><p>It's illegal (in many countries) to interfere with the power supply on a telephone - the reason you get a power supply provided is for use in emergency situations when there is no power.</p>
What's a land line??? ??
The telephone power is not for emergencies, it is for normal operation. Early phones had carbon microphones that needed the DC voltage to work and newer phones use the voltage to run the electronics. BTW, if newer land line phones run touch tone and auto dial off of the line power without being knocked out by a ring or a surge, it can't be that complicated.
<p>A real phones circuitry - and it can't draw much power - doesn't have to deal with ring voltages. As soon as the exchange detects the phone go off-hook, the line voltage drops, and it will not ring. </p><p>This is very important. There are specs for how quickly the off-hook detection/transition must occur. Some phones ring out the earpiece. Imagine answering one of these, putting the handset to your ear and getting one more ring... Right into your ear - ouch!</p>

About This Instructable




Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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