Newbie needs help with schematic

Discussion in 'The Projects Forum' started by BobS0327, May 21, 2013.

  1. BobS0327

    Thread Starter New Member

    May 20, 2013
    3
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    I want to build this http://blog.makezine.com/projects/make-34/the-dryer-messenger/ project.

    But I don't understand the schematic in the posted link. Specifically, I don't understand the 3.5 mm stereo jack connection. It's labeled as X1 but there are three connections labeled 1, 2 and 3. I have a female 3.5 mm connector attached to my Seed Current Transformer. This female connector has three wires. One of which is bare and is obviously the ground wire. The other two are red and black. I have my Seeed CT plugged into the female connection and I wish to wire the female connection into the circuit shown in the link.

    Any assistance would be greatly appreciated.
     
  2. edwardholmes91

    Member

    Feb 25, 2013
    181
    18
    I'm afraid I personally can't help you there, but I would like to see how you get along with this project because it looks really interesting! :) I have seen people do similar things that send them a message and let them know when the post has arrived!
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,088
    3,027
    Here is the schematic in question:
    [​IMG]
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,088
    3,027
    So you want to map bare, red and black conductors from your sensor to 1, 2 and 3 on jack X1?

    I think we need to know more about your sensor and how those conductors connect to it at the sensor end of the cable. It looks like pin 2 is meant to supply filtered low voltage to the sensor and the signal comes back to pin 1. As drawn it looks like the shield is going to pin 1, but I think that would be odd.
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    If the attached is the current sensor you have, then the schematic posted is correct. Notice on the attachment that the tip and the sleeve of the "stereo" pin are used, but the ring is not.
     
    Last edited: May 22, 2013
  6. BobS0327

    Thread Starter New Member

    May 20, 2013
    3
    0
    Ok, That makes sense. The tip is the input and the sleeve is the ground. Now I have to figure out which wire (the red or the black) on my female 3.5 mm connector is "connected" to the tip of the male 3.5 mm connector.

    I apologize if my question is very elementary but I'm a total electronics newbie.

    But any help would be greatly appreciated.

    Thanx
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Based on the drawings, I don't think polarity matters. Notice on the sensor drawing that both the tip and the sleeve are labeled "output," and on the schematic, that neither connection goes directly to ground. One goes to an input on the μC and the other is connected through a capacitor to ground, which provides DC isolation.

    Bear in mind that I have never worked with either an Arduino or the sensor, so as one of our members here says, "I could be wrong."
     
  8. upand_at_them

    Active Member

    May 15, 2010
    246
    29
    The jack has pins 1, 2, and 3 because it's a STEREO jack. Take a look at a stereo plug, it has three sections. This circuit just uses the tip and the sleeve.
     
  9. BobS0327

    Thread Starter New Member

    May 20, 2013
    3
    0
    Thanx. I finally figured the tip and sleeve connections by using a cable with 3.5 mm male connectors at both ends. I plugged one end into the female 3.5 mm connector and attached a 5 VDC source to wired end of the female connectors. By process of elimination, using a voltmeter to test the output of the tip and sleeve on the other male end, I was able to identify the wires assigned to tip and sleeve.

    Well, my next question would be whether or not a burden resistor would be needed in the circuit illustrated above. I was doing some internet searching and came across this http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface link which indicates that a burden resistor would be needed for the CT being used in the project since the current output has to be converted to a voltage output.
     
  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The burden resistor is a means of reducing the voltage from the CT to a range that is within the input limits of the Arduino. If you are using the circuit to measure the current through the mains circuit, a burden resistor is required. However, if you are simply using the CT to determine if a current is flowing through the mains circuit, no burden resistor is required.

    Don't forget that everything I post is just my opinion; I'm no expert.
     
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