i just moved into a new house and there was a payphone in the house.it was broken when i moved in.but the landlord gave me the key to the phone box to fix. i fixed it but nobody uses the phone box.

so what i was think was that there is 50V DC and 50mA coming out of the line into the house.if i could make a step down transformer to step the voltage down 4V and that would step up the amps to over 500mA. this is what comes out of phone charger in to a mobile phone.
so i would be able to charge a mobile phone for free.
does anyone see any problems that i might in counter

the only problem is if someone calls on the phone line 80V to 70V AC signal is sent down the line to make the ring sound and the telephone so that might affect my transformer.

can anyone give me any advice

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Blades the deadly killer

 

i forgot, i won`t have the telephone connected at all to the line.all i won`t the line for is to charge anyones mobile

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Blades the deadly killer

 

firstly i would like to tell you that there is no such thing as a DC transformer. you cant step up or step down DC voltages with a transformer. you basically need a changing flux for transformer action which DC cant do. instead of a transformer, we use a DC-DC converter for stepping up or stepping down DC voltages.

and yes the high AC for the ringing will effect any DC-DC converter. i would say this is a bad idea. even if somehow the phone line proves to be okay for this purpose building a charger for a mobile phone needs alot of design considerations.

 

It's not going to work. The amount of power you can take from an on-hook phone line is severely limited (by law and by electronics at the exchange) ans soon as you start to get into tens of milliamps (I can't remember the exact figure) the line switches to off-hook mode, and the voltage drops to about 12 volts. Also, you might want to do the calculations to work out how much money you'll be saving. If you phone charger puts out 4V at 500mA, then assumming it's 100% efficient (which it won't be of course) then that's 2 Watts. A 1KWHr unit of electricity is about what? 10p - 15p? So you can charge your phone for about 3 weeks for 15p. 5p a week. Thats charging your phone for 24 hrs a day 7 days a week for 3 weeks. For 15p. You cheapskate.
Also, I would like to point out to you that telephone companies rarely make a loss which is subsidized by the fat-cat chief executives. If you steal electricity from your telephone exchange, all the other customers are subsidizing your cheapskate behaviour.

 

What about the called ID's with no battery and no external power, using 50ma from the line.?

If I have 3 in the house, than I'm a criminal because stealing 150ma from the Telco !!

Steve

 

I had an idea of this sometime ago, free electricity provided by the phone company sounds like a very good idea.

how exactly would they know about it, why would it be illegal anyway???

some phones use more power than other phones whats wrong with utilising the extra power that isn't used??

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www.winpicprog.co.uk - Great PIC language tutorials.

 

But it's only tiny amounts, not worth bothering with!.

In the past in the UK there was no specific law about phone tapping (I don't know if there is now?), so the police prosecuted you for 'stealing the electricity from the phone company'.

Also in the UK, you could be heavily (unlimited!) fined for connecting non-approved apparatus to the phone line - this effectively bans any homemade telephone projects!. Any such item has to be sent away and tested for approval, a process with costs tens of thousands!.

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thanks for pointing out how much i would save. 15p does not sound like alot. i just thought it might be a good idea for free electricity.. the cost of buying the DC converter would not making it a cost saving idea but thanks for everyone help.

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Blades the deadly killer

 

csaba911 (weird name) wrote:
If your called ID's take 50ma from the line in on-hook state, then there's something wrong with them.

pike wrote:

You demonstrate an ignorance that is breathtaking. If you don't watch out, you could end up becoming president of the USA.
P.S. Sorry, pike, I take it all back, I've just noticed that your from Australia.