Hi, this is Wayne again with a topic “DIY Hacks & How To’s: Emergency Power from a Land Line”.
What do you do if the power is out, but you need to charge your cell phone to make an emergency phone call? Don’T worry, there’s plenty of power sources all around you. One of them is the phone line. You may have noticed that corded phones don’t need to be plugged into an electrical outlet. That’S because they’re able to get the power that they need directly from the phone line itself when the phone is not in use. There’S a constant dc signal of about 50 to 60 volts in the phone line and when it is in use this drops to between 6 and 12 volts and when the phone rings it changes to a 20hz ac signal of about 90 volts, the phone lines generally.
Even have power during a blackout. This is because the phone companies maintain their own backup power system. Before you try and tap into the electricity in the phone line, you should check it with a multimeter to see what you’re working with at my house, i measured an open circuit voltage of about 52 volts dc. Then i took some measurements with different load resistances and after some calculating, i worked out that the base signal pretty closely resembles a 52 volt dc source with a 628 ohm internal resistance. Basically, this means that i could run a 12 volt circuit at 64 milliamps, a 9 volt circuit at 68 milliamps or a 5 volt circuit at 75 milliamps.
This isn’t a lot, but it’s enough to charge a cell phone in order to power a cell phone or other usb device. You need to use a voltage regulator to bring the output of the phone line down to 5 volts, i’m using an lm7805 5v regulator. If you need different voltages, other voltage regulators are available, including variable regulators, that let you set the voltage level using some external components to make a simple phone line. Adapter. All you need is a phone cord, a 5 volt voltage regulator and a usb connector cable start by cutting open the phone cord and the usb cable and separating out the internal wires connect the red wire from the phone line to the first lead of the regulator. Then connect the green wire from the phone line to the second lead, then take the black lead from the usb cable and also connect that, to the second lead of the regulator and connect the red wire from the usb cable to the third lead.
If you can’t solder the wires together, because the power is out just bend, the leads of the regulator away from each other and tightly wrap each wire around the leads, this should make a good enough connection. This simple regulator circuit is able to safely convert the base signal on the phone line into something that you can use to charge your cell phone. However, many voltage regulators aren’t able to handle the ac signal that you’d receive if the phone rang.
So if you’re worried that you might receive a call, while the regulator’s hooked up to the phone line, then you may want to add a diode to protect the circuit. Once all your wires are connected plug the phone cord into the nearest phone jack and then plug your phone and charging cable into the usb cable, your phone should begin to charge, and in a few minutes you should have enough power to make a phone call. Well, thanks for watching and check back next week for more fun projects, you .