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What is the hall sensor doing

  1. Sep 12, 2015 #1
    Ok, if I have a transceiver circuit comprised of a RFID(with antenna-resonating to RFS) that has the capability of tag-tag communication and the RFID responds to a beacon signal from a RF source by transmitting in response to the beacon signal 2 (alive signal). Its electrically connected so as to provide a gate bias or other signal to the code responsive switch(CRS). A hall sensor(code responsive circuit) is disposed adjacent the tag’s antenna in order to sense receipt of the beacon signal. Only the beacon signal will resonate in the antenna which provides a micro-signal that can be sensed to the gate input in order to switch the CRS from one position to another in response of beacon signal
    Ok...what is the hall sensor function here? I am assuming the RF are generating an electromagnetic/magnetic field
    Thank you in advance
  2. jcsd
  3. Sep 12, 2015 #2


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    that was a real mouthful, hard to say what it's doing....

    show us a circuit diagram

  4. Sep 12, 2015 #3
  5. Sep 12, 2015 #4
    do I need the hall sensor?
  6. Sep 13, 2015 #5


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    I was expecting a real circuit diag., not a block diag
    your block diagram doesn't show how the RFID unit is communicating with the Hall sensor
  7. Sep 13, 2015 #6
    Apologies, this is all I have and that is the question...how is the hall sensor or one could use an inductive coupling that is adjacent to RFID functioning in this block diagram?? It " senses receipt of the beacon signal' ... I guess that is my question...what does "sense receipt of beacon signal' mean since this signal resonates in the antenna which in turn sends out a signal that can be sensed
  8. Sep 13, 2015 #7
    I was told that this hall sensor is the component that sends the signal to turn on the LED's ; But, I believe this is incorrect since the presence of the RFID that is sending RF which would be the component that initiates the signal to turn on the LEDS?
  9. Sep 13, 2015 #8


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    Did you gain this information aurally, so that it's possible you may have misheard the word?

    If it really is a Hall sensor .... maybe there is a need for the tag to not only produce identifying information, but to also be physically positioned in a certain spot when it is interrogated, and to this end they have made the tag magnetic?
  10. Sep 13, 2015 #9

    Vanadium 50

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    I don't see how this can be answered without a proper circuit diagram. We couldn't answer this without a diagram if we were talking about a resistor or a capacitor. Why should be able to do so for a Hall sensor?
  11. Sep 13, 2015 #10
    Well I don't think I have the proper circuit diagram; Its basically a battery powered lighter with wireless communications that illuminated different color LEDS
    I am assuming the Hall Sensor used is to detect the magnetic field created by the radio frequency but I am not sure of its function

  12. Sep 13, 2015 #11


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    The magnetic field component ( and the electric field for that matter) is VERY small in this situation and without doing extensive research to prove otherwise, I seriously doubt that a Hall sensor would be able to be triggered by it

    You really are giving us nothing to go on to try and help you
    1) .. is this actually a working system ? .... if so show us a few well lit and sharp pics of the overall system and the circuit boards
    with enough clarity that we can read part numbers
    2) .. do you have the part /type number for the Hall sensor ?

  13. Sep 13, 2015 #12
    I am sorry but this is all I have. I looked up the definition of RFID-Inductive coupling: from the definition below could anyone tell me in layman's term (still learning)
    what the hall sensor function is? I apologize in advance for my inability to convey this system

    the reader's antenna coil generates a strong, high frequency electro-magnetic field, which penetrates the cross -section of the coil area and the area around the coil Because the wavelength of the frequency range used (< 135 kHz: 2400 m, 13.56 MHz: 22.1 m) is several times greater than the distance between the reader's antenna and the transponder, the electro-magnetic field may be treated as a simple magnetic alternating field with regard to the distance between transponder and antenna A small part of the emitted field penetrates the antenna coil of the transponder, which is some distance away from the coil of the reader. By induction, a voltage Ui is generated in the transponder's antenna coil. This voltage is rectified and serves as the power supply for the data carrying device (microchip). A capacitor C1 is connected in parallel with the reader's antenna coil, the capacitance of which is selected such that it combines with the coil inductance of the antenna coil to form a parallel resonant circuit, with a resonant frequency that corresponds with the transmission frequency of the reader. Very high currents are generated in the antenna coil of the reader by resonance step-up in the parallel resonant circuit, which can be used to generate the required field strengths for the operation of the remote transponder.

    The antenna coil of the transponder and the capacitor C1 to form a resonant circuit tuned to the transmission frequency of the reader. The voltage U at the transponder coil reaches a maximum due to resonance step-up in the parallel resonant circuit.

    Operation principle of an inductive coupled system

    As described above, inductively coupled systems are based upon a transformer-type coupling between the primary coil in the reader and the secondary coil in the transponder. This is true when the distance between the coils does not exceed 0.16 l, so that the transponder is located in the near field of the transmitter antenna

    If a resonant transponder (i.e. the self-resonant frequency of the transponder corresponds with the transmission frequency of the reader) is placed within the magnetic alternating field of the reader's antenna, then this draws energy from the magnetic field. This additional power consumption can be measured as voltage drop at the internal resistance in the reader antennae through the supply current to the reader's antenna. The switching on and off of a load resistance at the transponder's antenna therefore effects voltage changes at the reader's antenna and thus has the effect of an amplitude modulation of the antenna voltage by the remote transponder. If the switching on and off of the load resistor is controlled by data, then this data can be transferred from the transponder to the reader. This type of data transfer is called load modulation.

    To reclaim the data in the reader, the voltage measured at the reader's antenna is rectified. This represents the demodulation of an amplitude modulated signal
  14. Sep 15, 2015 #13


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    There are 2 main types of hall sensors used ...

    1) acts just like an on/off switch in the presence /absence of a magnetic field
    2) is a linear device who's output is dependent on the strength of the magnetic field

  15. Sep 19, 2015 #14
    A Hall sensor is simply a device that detects a magnetic field. It is a doped semiconductor that has a voltage applied across it causing a current to flow (holes or electrons depending on the dopant). In the presence of a magnetic field these charges are deflected due to the Lorentz force which causes an additional voltage to develop. This voltage is proportional to the magnetic field strength. However, without seeing a schematic of your device it is impossible to determine the purpose of the Hall sensor.
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