DTMF signal through an electricity 220V 50Hz

Discussion in 'The Projects Forum' started by kirill2008, Sep 22, 2008.

  1. kirill2008

    Thread Starter New Member

    Sep 16, 2008
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    Hello!
    I apply to you to help with the following working out of the electronic device. I am going to design the device for DTMF remote control by ON/OFF of home electrodevices.
    I already have a scheme for this device, all necessary electronic details are bought and I need to collect it only. But starting to design and collect all scheme, I have many questions on which I can not find on them answers in any way, therefore has dared to address to your professional opinion and very much I ask you to me in it to help.:)
    The first some questions concern the scheme, namely:
    1. Whether are the right resistors on the INPUT of microcircuit КТ3170 and why their such nominal values?
    *** R3 =22K, R4=22K.
    *** R2 = 220 Ω :confused: Could I pick up the 600Ω ?:confused:
    2.Whether are necessity to choose higher than these values on the scheme are correctly picked up?
    3.Whether the microchip KT3170 will not burn/break down when the ring signal of a call from automatic telephone exchange will come?
    3.3 Could I really connect Line R to the Ground ?
    *** In our country for telephone line : Voltage -50V DC, Ring signal voltage 90 V RMS, *** SO important : minimum for load 600Om >>>>
    4.Why the athor just picked up 2N2222 transistors and their resistors 100Ω?
    4.4 Is it really necessary to protect the whole circuit ? If Yes it is, so How is it ? ;-))

    5.What is such *10KHz OSC* and how probably most simply and quickly it to design? Whether the sinusoid is necessary?
    ***Whether it is possible to design a meander generated by timer 555NE? Whether meander signal will prevent scheme КТ3170 for decoding coming DTMF signal?
    *** Whether to destroy this OSC when it will be connected to the scheme during a call? How could protect it ?
    6. How it is possible to control by remote caller or any GOOD IDEAs about it, that the home electrodevice has really TURNed ON after sending DTMF signal?
    6.* How could I know that the elctrodevice is not yet connected or was connected, may be for this moment I`ll disconect it after sending DTMF desired signal for it???:confused: could I add in cirsuit any extra chip for this purpose ?
    7. How it is possible to add the timer for this scheme that after two minutes, for example, will automaticly disconnect it from a telephone line?
    8. Whether it is necessary to build in the diod bridge on the INPUT of the circuit? If yes, it is necessary to take advantage of what diodes (whether will good the 1N4007?)
    9. How can I calculate the consumed power of the circuit and what is the enough AMPERage for power unit 5v for it ???
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    And now the important questions:
    A. How probably to transmit a signal to switch on the electrodevice or it to switch off?
    *** certainly it is possible to stretch a cable or many wires at the house, but this way is absolutely not convenient and is not aesthetic!
    I suggest it to transfer on already existing electroconducting infrastrucure in the house
    ***(220 V RMS 50 Hz, 3 contacts).
    Thus it is possible to take advantage of transfer of the same retranslated DTMF signal, but already on electroconducting infrastructure in the house. My question in the following: whether it is possible to transfer a shortest DTMF signal and whether it is forbidden it is the law, or there are what that restrictions agree to standards for house electroconducting and a current proceeding in it?
    *** and how it probably to carry out and what it is necessary to design for achievement of this signal to the certain electric socket in the house? Whether probably this signal to transfer in electrical infrastructure and whether will affect it serviceable work of others elctrodevices (as for example the TV, a stereosystem etc...)
    Whether Will stir the electric current counter in the house?
    B. Where can I find the info about it ?

    Excuse me, please for my English. Very much I ask you to help.
    In advance I thank :)
    With Best Regards.
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I can't help you much, but it is a neat idea. When you have it finished you might think about putting it in the Projects Collection, where the completed projects are put.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
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    632
    I only attempted to answer the questions I thought I could answer.

    3.3 Could I really connect Line R to the Ground ?
    *** In our country for telephone line : Voltage -50V DC, Ring signal voltage
    90 V RMS, *** SO important : minimum for load 600Om >>>>


    ==> No, don't ground it. Let the phone company take care of the grounding.

    4.Why the athor just picked up 2N2222 transistors and their resistors 100Ω?

    ==> The 2N2222 is probably fine for driving the relay. I question whether the 100 Ohm resistor is appropriate - it may be increasing the dissipation on the D latches unnecessarily. Make sure you have enough base drive, then some margin (I use 2:1), but no more.

    6. How it is possible to control by remote caller or any GOOD IDEAs about it, that the home electrodevice has really TURNed ON after sending DTMF signal?

    ==> You would have to add feedback to the caller, such as a tone to indicate that the task was completed.

    6.* How could I know that the elctrodevice is not yet connected or was connected, may be for this moment I`ll disconect it after sending DTMF desired signal for it???:confused: could I add in cirsuit any extra chip for this purpose ?
    ==> That is something else you can invent.

    7. How it is possible to add the timer for this scheme that after two minutes, for example, will automaticly disconnect it from a telephone line?

    ==> It may be that IC2 automatically disconnects the telephone line after receiving the command. Check the circuit logic.


    8. Whether it is necessary to build in the diod bridge on the INPUT of the circuit? If yes, it is necessary to take advantage of what diodes (whether will good the 1N4007?)

    ==> What would you use the output of the diode bridge for? Diode bridges are used in telephone line connected devices that are powered from the telephone lines so that in case the wires are reversed, the circuit will still work.

    9. How can I calculate the consumed power of the circuit and what is the enough AMPERage for power unit 5v for it ???

    ==> Basically, divide the power supply voltage by the parallel resistance of the most relays that will be on at one time. It is unlikely that the rest of the circuit draws much power.

    ||||||||||||||||||| You will have to come up with a well isolated (floating) 6 volt power supply for this project since you should not ground the telephone line. Be careful of leakage that would put hum on the line and cause the telephone company technician to come around looking for the source of the hum!
    |||||||||||||||||||
     
  4. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    Thank you, I`ll do it:)
    With best regards,
    Kirill
     
    Last edited: Sep 22, 2008
  5. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    Thank You so much for your help.
    With best regards,
    Kirill
     
  6. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    All the same, Could I connect the "ground" or Colud I design anything else for prevent the HUM ?
    How do You think about it ?:)
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I assume (without knowing) the KT3170 is a DTMF decoder chip. I am not familiar with it in the slightest.

    600 ohms is the telephone standard. Again, I assume the 220 ohm resistor is the pick up value. Since this isn't a telephone line you're connecting to you can change some of the assumetions though.

    You'll need to look at the specs for the KT chip to see if it needs to be a sine wave or not, I'm betting it's not critical since this is fundamentally a digital circuit.

    I'm not too clear on several points though, are you wanting to use the power lines as the transmission medium? Or turn on/off appliences using the telephone line?

    If you do need a sine wave turning a stable 10Khz square wave into a sine wave really isn't that hard, so (assuming the 555 is stable enough) you can start with a 555 circuit, or go with a sine wave oscillator.
     
  8. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    1. KT3170 - clone of MT8870 (the same characteristics)
    2. 10 KHZ OSC just gives audible warning to a remote caller that the device ( I mean the decoder MT8870/KT3170) is switched ON and it is ready to recieve the DTMF signal.
    If I assume 10KHz SQUARE wave, IS NOT INTERFERING signal for proper/correct recieving of DTMF signals by MT8870/KT3170 ??? Or I have to use just SINE wave ??
    3. Yes, I mean to transmit secondary DTMF signals after decoding by the circut over power lines (220V). Secondary DTMF signals could be good control signals to switch ON/OFF electric appliance.
    But my question is it permitted/admitted by the law and Will not this transmission of the signals destroy other electric appliences?
    4. The project is based on TWO transmission mediums :
    First medium - telephone lines - for remote caller and for the decoding circuit
    Second medium - power lines - for desired electric appliences

    with best regads,
    Kirill
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    OK, let's keep it simple for now.

    Using power lines for data transmission is not new, I've bought remote phone jacks that use the local house wireing for connection. I didn't see any provision for that on your setup. I'm not familiar with the laws in other countries, but in any case even if it is legal you need to proceed with extreme caution, as telephone circuitry and high voltages do not mix well. I suspect a transformer/cap will do a good job of coupling.

    Their are several options on the 50Hz hum, my first impression is a high Q active notch filter, but there are other ways, such as special hybrid transformers. Other people may have better ideas.

    Your relays are going to be the big draws. Add the current they will all use, then add another 100ma for the solid state electronics, and you'll have an approximation of your current requirements.
     
  10. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    Thank for your help!
     
  11. DickCappels

    Moderator

    Aug 21, 2008
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    The telephone companies do not expect subscriber equipment to ground their lines. There are safety concerns for both the telephone company equipment and personnel, as well as more mundane functional and line quality conerns. I think the best policy is to look as much like a telephone as possible so it does not disturb their world.

    Remember, telephone employees will be occasionally touching your line with their bare hands, expecting to only be grabbing 48 volts (unless its ringing, of course!:eek:). You have a strict responsibility when you connect equipment to the telephone lines to make sure that it conforms to the relevant standards.

    In the United States, the relevant standard is Title 47, Part 68 of the Code of Federal Regulations. You should be able to read through it on the web.

    PART 68—CONNECTION OF TERMINAL EQUIPMENT TO THE TELEPHONE NETWORK

    http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/cfr/1999/47cfr68.pdf

    It may look like dry reading, but it has schematics and block diagrams, and for somebody interested in telephone circuits, its heady stuff.:)

    BTW, with respect to Bill_Marsden's post, from my experience in the days of relay switching offices (before the SSS officers were introduce), 220 Ohms was an excellent value for a pickup resistor. I doubt that has changed.
     
    Last edited: Sep 23, 2008
  12. kirill2008

    Thread Starter New Member

    Sep 16, 2008
    7
    0
    I am very grateful to you for the given information ;-)))
    With beset regards,
    Kirill
     
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