power supply from phone line

[kovic]

hi;

i have ring indicator circuit but i want to get the power from the phone line. i use a 5 volt battery for the supply. does anybody knows can i get the power from phone line.

i need 50mA 5V dc.

thanks for your consideration.

 

[flatulent]

power from phone line

This may not be legal in your country. You should check with the laws. The other problem is that your current may trip the off hook condition and you will not get any incoming calls.

 

[kovic]

power supply from phone line

it is not a problem. we have a small switchboard and we can dedicate an extra line just for it. if you have circuitry about it can you please help me. iwant to use the ring indicator with a relay and to control the doors or whatever you want.

 

[batdin]

phoneline power supply

A short-circuited phone line(at least where I live) gives about 40mA.It means you can't deliver 50mA using a conventional regulator.But if you use a pulse mode regulator(let's say using MC34063),I think it may be possible to do it.The only problem I can see may be an eventual oscillation because of the inherent negative load resistance of the switch-mode power supply and the relatively high resistance of the phone line.But it's easy to put this to test.

 

[Externet]

phone line power

Hi.
The maximum power that the telephone line can supply depends on the distance to the central office substation.

You can find out with a volt meter and a current meter, and a 500Ω variable resistor.

Set the potentiometer across the wires to get 5 V, check if the current reaches 50mA.

If yes, you must observe polarity. Insertion of a polarity streering bridge would decrease the voltage.

Miguel

 

[aylak]

how to get power from telephone line

maybe it is useful for you

 

[pool_77]

getting power from your phone line

maximum allowed power is 300mW

pool

 

[kovic]

use phone line power

thank you for your consideration. but your circuit is aprofessional one, i think. i am trying to solve it without ICs.
thanks again.

 

[skydiverc]

power supply using telephone line

This may not be legal in your country. You should check with the laws. The other problem is that your current may trip the off hook condition and you will not get any incoming calls.

If you pull over 10ma you will trip the off hook sensor at the phone company.
I dont know the actual minimum to detect that without researching.
When this happens if you dial the # your circuit is on you will get a busy signal and your circuit will not see a ring to detect.
That is your problem in a nutshell.
You must not trip the off hook condition at the switchboard while powering your circuit.

The only way I can see this working is if you use one phone line strictly as a power supply and a different phone line for ring detection.

Wouldn't it be easier to just use a 9v battery with a low current led indicator for battery ok.

 

[platonas]

power supply from telephone line

You may use a superCap and charge it by limitting the current to 5 ma. Then this could supply your cct.
Only for some small time the charging proccess will absorb current from the tel line.

 

[papyaki]

5v telephone line power

Hi,

Maxim has a good schematic

h**p://www.maxim-ic.com/appnotes.cfm/appnote_number/427

Replace * by t

 

[platonas]

do phone lines have power supplies

Maxim has a good schematic

h**p://www.maxim-ic.com/appnotes.cfm/appnote_number/427

But this circuit does not serve the purpose, it only operates when you pick-up the handset. In the on-hook position is off. And it does not convert 48V to 5V but the off-hook voltage (arround 9V-12v) to 5V.

 

[nikhilele]

phone line resistance

i tried to short the phone lines with 4.7kohm resistor and when i called to that number the phone company says phone busy and ring is not detected at my home.

how to get continuous power from the phone line.

MY CALLER ID is doing it nicely it shows time round the clock and when somebodys calls up it shows it number on backlighted lcd. So how my caller id is managing power. it doesnot have any adapter.

 

[servicemann]

get power from a telephone line

Your caller takes just VERY small current.
Probably less then 1mA. For LCD it is enough.

 

[nikhilele]

how to check phone line power

caller id consists of many other things, as it is showing date and time. it must me having dtmf decoder, microcontroller probably RTC. and back lighting lcd needs power.

 

[haerifar]

power from off-hook phone line

if you use tel line , your phone will not work because the company's swith found your phone was online and waiting for your contact and after some second you did not any contact and your phone line going to Emergency mode .. (in my country maybe the same as your company ) anyway please inform us .

 

[artem]

power supply from off-hook phone line

I so this kind of circuit while ago which was operated from telephone line without disturbing it at all .
TO start with that you have to figure out requirement of leackage current for telephone line when line is OFF and necessary power on output side . If input (drawn from line) and output converted to supply your load do not much (take care about conversion loss estimation as well) - that will be impossible to do (from law point of view).

The first should be based on domestic or international standards . Convertor itself was something like transformator based dc -dc converter operating directly from 48 V.
What you have to design is miropower dc-dc converter.

Just little add - 5 V 50 mA is about 250 mW, i remember leackege current for some of the countries were limited to 100 uA, so power possible to drawn from line is 4 mW . quite low indeed and seems it is impossible to make such circuit (5 mA current from 48 V is not real for off line).

 

[sihuijian]

I think first your circuits quiscent supply need not exceed 5mA(or phone line is busy),second your circuits can accept 100V input( when the ringtone arrives it will reach 100V),last our country standard phone device quiscent supply must not exceed 0.5mA(if telephone it must not exceed 50uA).