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Prop/RJ 45 question — Parallax Forums

Prop/RJ 45 question

CameronMCameronM Posts: 57
edited 2010-06-16 22:56 in Propeller 1
·Is it possible to use a RJ 45 jack with an ethernet cable to send a signal from the prop to lite up an LED on the other side of the cable? Would any additional hardware be required or can I just·do·this directly from the prop?

Thank you,

CameronM

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-16 13:31
    Yes, it's possible. An ethernet cable is just a bunch of wires. If you want to use a really long ethernet cable, there'll be significant resistive losses in the cable and you'll have to account for that. Remember that, although the Propeller is a pretty robust chip, it can be destroyed in an instant if connected to the wrong voltage and you will have a bare I/O pin "hanging out there" at the end of a cable that looks like lots of other cables. It's usually better to have some cheap, easily replaceable device like a switching transistor between the Propeller I/O pin and the outside world.
  • CameronMCameronM Posts: 57
    edited 2010-06-16 17:26
    ·Thank you for the quick response. That's what I figured but was not 100% sure. Why I asked was because I had recently purchased the RJ 45 Ethernet magjack from sparkfun with the breakout board, but when I go to send out a signal nothing happens, its almost as if the signal is not even being transmitted. Could this be because of the transformer in the RJ 45 Ethernet magjack?

    Here is the·link to the RJ 45 Ethernet magjack.


    http://www.sparkfun.com/commerce/product_info.php?products_id=8534


    Thank you,

    CameronM
  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-16 17:31
    An RJ45 magjack is not the same as an RJ45 jack. The magjack has a bit of other stuff in it. In particular, there's an isolation transformer to prevent DC or low frequency AC current from flowing through it. Look at the datasheet for the magjack and find the internal schematic for it. You'll see.
  • schillschill Posts: 741
    edited 2010-06-16 17:33
    You will need a jack that doesn't have the transformer (etc.) in it. Something like one of these from sparkfun:

    http://www.sparkfun.com/commerce/product_info.php?products_id=643
  • Timothy D. SwieterTimothy D. Swieter Posts: 1,613
    edited 2010-06-16 22:56
    Just a regular RJ45 jack with nothing fancy. Just plastic and pins is what you will need. Just like Schill posted.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Timothy D. Swieter, P.E.
    www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" 16:9 LCD Composite video display, eProto for SunSPOT, PropNET, PolkaDOT-51
    www.tdswieter.com
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