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    Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Hi
    I want to transmit data over copper telephone line by using two ADSL modems up to 1Km distance. The first ADSL modems must be connet to a DC motor driver that support ethernet protocol and another ADSL modem connect to my PC by ethernet cable. Is it possible to do it?

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    Point to point LAN extension

    Hi
    I want to build an underwater videometry robot and i want to connect two ADSL modem back to back(by twisted wire or telephone line wire) to transmit data.Is it possible two connect two ADSL modems or two cable modems together and create a point to point Lan extension?
    Thanks.



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    Re: Point to point LAN extension

    It almost certainly won't work. ADSL works in a master-slave relationship with equipment at the telco so joining two back to back would leave both with no master clock to synchronize them.

    You CAN do it with older analog modems (the ones that audibly warble) but the speeds probably wont exceed 2400 bauds which may be too slow for your needs. If you want to try, I suggest you add a line attenuator between them, a 300 Ohm resistor across each modem's line connection and also 300 Ohms in each leg of the wires between them otherwise you may overload their input stages.

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    Re: Point to point LAN extension

    Thanks Brian, I found in the web that I can do this by SDSL modem, but thay are very expensive. Do you have any suggestion for me to transmit data by high baud rate up to 1 Km? I need to transmit several sensor information and TCP/IP camera video.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Hi,

    high baud rate
    "High" is no specification. Give a value.

    Klaus
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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Google for "DSL modem leased line" and review available commercial products.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Before looking further, when you say "over copper telephone line" do you mean a normal line as you would have at home or is this an independent wiring installation that only joint the two ends without going through other equipment?

    If you simply want to transfer data over long distances, RS422 or RS423 would be a better and cheaper solution and they can easily work at high speeds (>100Kb) over more than 1Km but they normally use twisted wire pairs. I'm not sure you can rely on telephone wires being good enough though over such long distances. I normally use CAT5 or CAT6 cables and RS422 for long full-duplex high speed links.

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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Thanks Klaus. In my robot i has these equipment:
    1. TCP/IP camera with meduim resolution of 0.4MP (720×576).
    2.Gyroscope sensor.
    3.Sonar sensor.
    4. Incremental encoder for distance measurment.
    5. lasser Sensor.
    I need to see TCP/IP camera video online with 30 frames per second and another sensor need to refresh each one second in the operator side. Do you have any suggestion to transmit these data up to 300 meters?



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Hi,

    Thanks Klaus. In my robot i has these equipment:
    1. TCP/IP camera with meduim resolution of 0.4MP (720×576).
    2.Gyroscope sensor.
    3.Sonar sensor.
    4. Incremental encoder for distance measurment.
    5. lasser Sensor.
    I need to see TCP/IP camera video online with 30 frames per second and another sensor need to refresh each one second in the operator side. Do you have any suggestion to transmit these data up to 300 meters?
    ...you don´t expect me to calculate the data rate?

    Klaus
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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Thanks Brian.
    I work on a sewer inspection robot. In the first step it’s satisfying to transmit data up to 300 meters. I need videometery and some another data collection. Traditionally in the sewer inspection robot used coaxial cable for CCD analog camera video transmitting and RS485 for other sensors data. The sewer inspection robot cable is very expensive and it just suitable for CCD analog camera. also, these cables need big space to collect them. I want to use digital camera for better resolution. I thought that I can use ADSL technology to used two wire twisted cable for video and data transmitting. Can i use RS423 and RS422 for video and data transmitting? if not, suggest me a good solution.
    Thanks.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    If the camera uses TCP/IP you would be foolish to convert it back to some other format and then back again. Your optimum solution is to convert all your data to ethernet protocols, if it isn't already, so it matches the camera data format then use a fiber optic converter at each end. That will give you more bandwidth than you need and a much longer cable length limit. Your alternative is to use CAT5 or CAT6 cable and add a hub every 100m but you would also have to carry power to them along a second cable. There is a limit to how far you can extend using hubs before the packet delays accumulate to the point where a response can't be received before a timeout but it should be considerably longer than 300m.

    Brian.

    Afterthought:
    If you buy a cheap Raspberry Pi and camera, you can add the other sensors as peripherals and make it talk down a single CAT5 cable. The standard camera is 8M pixels so far higher resolution than your present one and the whole thing is so small it can easily be fitted in a small watertight box. I use them as cheap security cameras, the Pi and camera costs a lot less than a normal commercial device.
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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    My robot work in harsh environment, one solution is fiber technology but they are Fragile. Can i implement ADSL technology in my own board in a master-slave relationship?

    - - - Updated - - -

    Thanks, fvM, DSL leased line modem need fiber. my robot must work in harsh environment and the cable must Wrap round the reel. The fiber is very fragile.

    - - - Updated - - -

    your suggestions are very nice, is it possible to wrap fiber round the reel?

    - - - Updated - - -
    Last edited by H2M; 15th June 2018 at 10:23.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    DSL leased line modem need fiber
    No. By definition of term, DSL uses telephone lines. I just noticed, that some products are advertized, didn't check about prices and availability.

    Regarding previous discussions about data rates over telephone lines. Modems trade signal dynamic against data rate by using complex modulation methods. You need something like DSL to achieve multiple MBit data rates over 1000 m twisted pair.

    A possible technical platform to build the link could be also a power line modem chip set.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Thanks Brian, I promise this will be my last question! In my sewer inspection robot i have to use a power Cable for Power Circuits in my robot. the good solution is to use power line modem networking and transmit power, TCP/IP camera video and sensors data over it. you said that ADSL technology need telco for synchronization. is it possible to use power line modem in offline configuration? i mean this is necessary connection to internet for synchronization.



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    There was a discussion in another forum recently, with some links to modems that can operate "stand alone".
    I can't find the thread, unfortunately, but it was devices like this: https://www.netsys-direct.com/produc...-nv-202rpcekit
    A keyword for hardware search might be "Ethernet extender"
    https://www.blackbox.com/en-us/produ...king/extenders



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    is it possible to use power line modem in offline configuration?
    Maybe, but it would depend on the exact model. To use TCP/IP in a simple network there has to be one controller in the network that can allocate IP addresses (a DHCP server) so you would have to find one with that facility AND a second one that can have the facility disabled. You can't have two DHCP servers in the same network or they will both try to allocate addresses and both will fail. If you have a manged hub or router with DHCP you might be able to use it at the monitor end and use a power line adapter at the other.

    As the environment is harsh, you can still try for flexible optical cable, it is plastic with several layers of sheathing and quite tough, or you could use 'outdoor' grade CAT6 cable (that's what I use) which is normal CAT6 twisted pairs but with an additional heavy grade outer layer. It's a real pain to connect to because it is thicker than normal CAT6 and you have to remove the outer sheath some way back before fitting a plug but it can be coiled tightly. In fact I buy it in 300m coils and achieve 1Gb/s throughput over >100m distances. Being Al/Cu wires, it will eventually work harden and break but it is inexpensive and should last for many work cycles. This is the stuff I buy:
    https://www.amazon.co.uk/Outdoor-wat...s=outdoor+cat6

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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    Thanks Brian, I bought a pair of power line modem and now i can control the robot over my home power circuitry in offline configuration. Since the robot must work in the sewer pipe wich is a humid and wet environment, I should reduce AC power from 220 to under 100 volts. Is 100 volts AC power dangerous for human?
    I have three methods to make 100 volts AC signal:
    1-Use transformer
    2-Use AC/AC inverter
    3-Use DC/AC inverter
    Which of these solutions has less risk for human?



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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    1. is the only really safe way. The other methods might work but they have drawbacks, mostly to do with how clean their output voltage is. Inverters work by rapidly chopping the input voltage so it's frequency is higher, that allows the use of smaller and cheaper transformers but without knowledge of the interior circuits, it is quite possible for them to have no isolation between input an output sides at all. Also, they tend to produce noise (spikes in the AC waveform) which are likely to jam the data you are sending along the same wires.

    100V is more than enough to kill someone but there is an old saying: "it's volts that jolts and mils that kills", meaning that any voltage high enough to push current through you is dangerous. Even 12V can give a kick if your skin is wet and therefore more conductive. I've survived (obviously) 25KV+ shocks but with dry skin so the current couldn't easily flow, if I had been more conductive I would have had an instant cremation!

    One 'gotcha' to be aware of, the power line modems superimpose a high frequency data stream across the AC wires so you don't want to do anything that would short out or reduce that stream. It is possible, depending on the exact type, that a transformer to drop the voltage would also partially absorb some of the data amplitude. If you follow the transformer suggestion, I would suggest you buy four small wire chokes with a value of say 500uH and wire one choke in series with the AC wires at each end with the modems 'inside' the chokes. In other words the modems are connected across each other via the AC wires but there is a choke between the wires and the transformers. It will help to isolate the data level from being pulled down.

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    Re: Transmit data by Connect two ADSL modems over copper telephone line up to 1KM

    The electrical safety problem is beyond the original thread topic and also not fitting the digital communication section. You better start a new thread.

    A short comment though. Limit value for safe low voltage circuits is 42 VAC in normal (dry) environment, but it's not applicable in the said situation. You need to deal with the fact that even lower voltage is a hazardous contact voltage and watch out for additional safety means, e.g. RCD.



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