Using a sensor to sense the presence of copper wire.



  • Newbie here, attempting to create a fixture that will use a sensor, that will signal when there is the presence of copper wire.

    The wire inserted into the area of the sensor will vary from:

    36 ga. - 5 ga. Magnet wire
    24 ga. - 10 ga. Stranded wire with the insulation removed.

    Any idea which direction I should go for a sensor?

    Thank you, Jay


  • Mod

    @moparjay Does it have to detect copper wire only, or just the presence of any wire/thing?



  • It can detect anything, but the only thing that will be inserted into the area will be bare copper. Some of it, very small.


  • Mod

    What are you trying to build?



  • It's an enclosure with a hole where the wire will be inserted into. The wire will be detected by a sensor, signal making it's way to a solenoid that will activate a pneumatic cylinder that will extend and clamp the wire in place....making contact.


  • Mod

    If you need a precise measurement you could use a laser diode and its sensor, the when the wire is inserted at a certain length it will block the laser and you know something is there to be grabbed. Otherwise some magnetic sensor that detect a change in magnetic field, but it is all down to the accuracy you need



  • Other than the accuracy of being able to detect the wide range of wire, this can be rather crude. No accuracy needed with the depth of the wire being inserted through the hole in the enclosure.


  • Mod

    @gohan copper isn't magnetic 😉


  • Admin

    Bare copper should reflect light. What about sending off ir light (with some dampening material on opposite the other side). And a shielded ir sensor next to the sender to detect the reflected light?

    You could perhaps try with one of these:
    https://www.ebay.com/itm/5X-IR-Infrared-Obstacle-Avoidance-Sensor-Module-Detect-Distance-for-Arduino-DIY/142649289652?hash=item21368f6bb4:g:nAQAAOSw-4RaUyOd


  • Mod

    @mfalkvidd I know but it should interfere with an electromagnetic field, right?


  • Mod

    @gohan I don't think it would



  • The smallest wire to be detected is only .005" in diameter (.13mm). I think this will be tricky using a reflective type sensor. Please correct me if I'm wrong, I have very little knowledge in this field.


  • Mod

    @moparjay what is the accuracy you are looking for?



  • The maximum distance needed to detect is 6mm from the sensor. Or if the sensor is the type where breaking a beam is used, it will need to be able to break the beam with wire as small as described above.


  • Mod

    I mean if there is a specific length of the cable that gets inserted before it gets detected and if that length needs to be very precise. Maybe a small IR frame like those used to make touch surfaces would do?



  • No....not at all. Just insert the wire, creating a signal, activating the cylinder, clamping the "bare" wire.

    The wire will then be sandwiched between the shaft of the cylinder. and an aluminum contact....which will carry the very small current of the wire.

    The wire will be inserted through a hole on the top of the enclosure, travel down past the aluminum contact (and cylinder), then just below will be a sensor.

    I'm unfamiliar with the "small IR frame like those used to make touch surfaces".



  • Capacitive switch sensor like the AT42QT1011 maybe?

    Something along the lines of https://www.sparkfun.com/products/14520

    Only thing I'm not sure of is whether the copper wire would trigger the capacitive sensor, although if its being inserted by hand then it should have a charge from your own bodies natural charge as well possibly? Or if it is being fed a charge by something else that is touching it, then it might be enough.



  • The wire(s) will be inserted by hand, but only the first inch of the wire is bare/striped. The remaining length of wire will still have its insulation. Sadly, the operator cannot be a part of the circuitry. LOL


  • Hardware Contributor

    @moparjay said in Using a sensor to sense the presence of copper wire.:

    The maximum distance needed to detect is 6mm from the sensor. Or if the sensor is the type where breaking a beam is used, it will need to be able to break the beam with wire as small as described above.

    There are also time of flight sensors, they use a laser and measure duration for some light to come back after a small "flash" of a laser led.
    I am not sure at all it can detect at such a short distance and if reflexion would be strong enough on your smaller wires, but it's worth a look at the data sheet. They don't need laser beam to be broken and they don't measure the quantity of light that is reflected so in theory it can work.
    Long distance version (up to 2m, not suitable for you) is vl53l0x by ST, search for it and you should find the version for short distances on their website. And there are probably other chips from competitors as well.





  • @moparjay
    I have a question : Does your project measure the wire form end to end or can it detect just the presence of copper wire and does it only see copper?
    I have a HF tuner project that scans for antenna on the system and because some antenna have no real return other then RF your project may be able to see the wire in that antenna and return a controllable reading.
    thanks



  • No measuring of the wire.
    It only has to sense the presence of copper wire.
    The wire being inserted into the enclosure is not part of any circuit, and will have no electrical field.



  • @moparjay
    So if I understand you right , If you insert a copper wire you get some kind of feed back.



  • I'm hoping to find a way to insert a bare copper wire thru a hole in an enclosure, then have a sensor that sees the presence of the wire, and the sensor sends out a signal to relay, that sends a signal to a solenoid, that activates a pneumatic cylinder, that will clamp the wire in place.



  • @moparjay
    I think I under stand now what you are doing now.
    How far are you , maybe I can help out.


  • Mod

    @moparjay how about building a simple metal detector circuit like this : https://www.electronicshub.org/metal-detector-circuit
    If you stick the wire through the foil it'll probably be able to detect it



  • Please see attached image:

    0_1521480421127_20180319_131030-001.jpg



  • @yveaux That would not work because the case is all metal to block RF .


  • Mod

    I am assuming that having a "close" and an "open" button is not an option, right?



  • The button you see mounted in the pic, is a momentary (normally closed) switch.

    If I can find a sensor to work properly, this will be used to open the spring loaded cylinder manually by the operator "after" the signal is sent to close the cylinder.

    If the sensor automation does not work out (to close the cylinder), the button will be to manually open the cylinder that will "always" be in the closed position. Push the button, cylinder opens, wire inserted, release button, cylinder returns to it's normally closed position.



  • The plan was to have this contraption automated in the clamping motion. Simply insert wire, sensor sends signal, closes the cylinder to clamp the wire in place.

    But if this is too difficult, I'll resort to Plan-B, which is having the cylinder always pressurized in the "clamp" position or "closed" position. Push the momentary, to open the cylinder, insert the wire, release the button, cylinder returns to closed / clamp position.

    The photo is only a test piece for experimentation. The REAL unit will be enclosed with a row of many cylinders / contacts / etc., with the ability to hold many different wires at once, all independent from one another.


  • Mod

    Given the variety of the wires diameters, I think the 1 or 2 buttons solution is the most reliable one. Just my 2 cents



  • @gohan said in Using a sensor to sense the presence of copper wire.:

    Given the variety of the wires diameters, I think the 1 or 2 buttons solution is the most reliable one. Just my 2 cents

    I agree.

    I can accomplish what I want with a single momentary. So, it's no big deal....just hoping to make it more automated.

    My original plan was to use a proximity switch. But I quickly learned the issues with consistently detecting copper.



  • @moparjay
    How about a pressure switch .
    I must be missing something here, what is the end point ?



  • How about a pressure switch .

    If you are referring to a pressure switch for the wire to apply the pressure, the wire will be as small as a human hair. Not capable of applying pressure.



  • @moparjay
    have you thought about using a jfet?

    see here for a google search




  • Mod

    It looks interesting, but I haven't seen if it may work with copper too



  • have you thought about using a jfet?

    Thanks for the info. But I'm fine with the simplicity of a momentary, if full-automation-clamping is too difficult...or expensive. LOL



  • @moparjay
    what about when sliding the wire into the top hole you give it a + charge and the base a - charge with a circuit that will do when the 2 touch.



  • what about when sliding the wire into the top hole you give it a + charge and the base a - charge with a circuit that will do when the 2 touch.

    If the range of wire size was tighter, this would probably work well. But with the wide range of sizes, trying to make contact with the smallest sizes would be a real pain.



  • @moparjay
    how about an "S" shape input tube any size would have to touch the tube on the inside the "S" shape tube can be any size you like.



    1. Optical detection: a light source on one side of the hole and a phototransistor on the other, read as analog values since the small wires won't completely cover the light source

    2. Inductive sensor, a coil around the hole, and some form of detecting the change of inductance, start by making a small coil and test with a LCR meter

    3. Capacitive sensor, open air dielectric, plates across the hole, the wire and operator (even holding the insulated wire) will change the capacitor response a lot, test with some capacitive/touch sensing circuitry.



  • Thanks to all that have given input. I'm going to give in and simply use the momentary to open the cylinder (normally closed). It's just too easy. And going automated is not worth the added expense, as this single cylinder prototype will be duplicated to almost (100) cylinders....each completely independent from one another. Thank you!!!


 

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