Login | Register | Advertise | About Us | Contact Us  
 
   
    H O M E   >>  C I R C U I T   L A B














Skin Response Meter
 

Related Circuits

  • Simple Antenna Preamplifier for AM Radios
  • Bhajan and Mantra Chanting amplifier
  • Simple Stereo Level Indicator
  • 1.5 Watt Power Amplifier
  • Over-Speed Indicator

  • Subscribe to Electronicsforu.com
       

    SKIN RENSPONSE METER  

    D. MOHAN KUMAR


    Human skin offers some resistance to current and voltage. This resistance changes with the emotional state of the body. The circuit proposed here measures changes in your skin resistance following changes in your mental state.

    In the relaxed state, the resistance offered by the skin is as high as 2 mega-ohms or more, which reduces to 500 kilo-ohms or less when the emotional stress is too high. The reduction in skin resistance is related to increased blood flow and permeability followed by the physiological changes during high stress. This increases the electrical conductivity of the skin.This circuit is useful to monitor the skin's response to relaxation techniques. It is very sensitive and shows response during a sudden moment of stress. Even a deep sigh will give response in the circuit.

    The circuit uses a sensitive amplifier to sense variations in the skin resistance. IC CA3140 (IC1) is designed as a resistance-to-voltage converter that outputs varying voltage based on the skin's conductivity. It is wired as an inverting amplifier to generate constant current to skin in order to measure the skin resistance.

    IC CA3140 is a 4.5MHz BiMOS operational amplifier with MOSFET inputs and bipolar output. The gate-protected inputs have high impedance and can sense current as low as 10 pA. This device is ideal to sense small currents in low-input-current applications.

    The inverting input (pin 2) of IC1 is connected to ground (through preset VR1) and one of the touch plates, while the non-inverting input (pin 3) is grounded directly. The output from IC1 passes through current-limiting resistor R1 to the second touch plate. R1 act as a feedback resistor along with the skin when the touch plates make contact with the skin. So the gain of IC1 depends on the feedback provided by R1 and the skin.

    In the inverting mode of IC1, a positive input voltage to its pin 2 through the feedback network makes its output low. If the skin offers very high resistance in the relaxed state, input voltage to pin 2 reduces and the output remains high. Thus the gain of IC1 varies depending on the current passing through the skin, which, in turn, depends on the skin response and emotional state.

    In the standby state, touch plates are free. As there is no feedback to IC1, it gives a high output (around 6 volts), which is indicated by shifting of the meter to right side.When the touch plates are shorted by the skin, the feedback circuit completes and the output voltage reduces to 4 volts or less depending on the resistance of the skin. Since the feedback network has a fixed resistor (R1) and VR1 is set to a fixed resistance value, the current flowing through it depends only on the resistance of the skin. The output from IC1 is displayed on a sensitive moving coil meter (VU meter). By varying preset VR2, you can adjust the sensitivity of the meter.

    For easy visual observation, an LED display is also included. IC LM3915 (IC2) is used to give a logarithmic display through LED indications. It can sink current from pin 18 to pin 10 with each increment of 125 millivolts at its input pin 5. Using VR3 you can adjust the input voltage of IC2, while using VR4 you can control the brightness of the LEDs.

    In practice, the circuit provides both meter reading and LED indications. If the LED display is not needed, IC2 can be omitted.

    Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet with touch pads glued on the top, 5-10 mm apart. Touch pads can be any type of conducting plates, such as aluminium or copper plates, having dimensions of 1XC1 cm2. The moving coil meter can be a small VU meter with 1-kilo-ohm coil resistance and 0-10 digit reading.

    After assembling the circuit, adjust the presets such that IC1 outputs around 6 volts. None of the LEDs (LED1 through LED3) glows in this position with the touch plates open.

    Now gently touch the touch plates with your middle finger. Maintain the finger still allowing one minute to bond with the pads and keep your body relaxed. Adjust VR3 until the green LED (LED1) lights up and the meter shows full deflection. Adjust VR2 to get maximum deflection of the meter. This indicates normal resistance of the skin, provided the body is fully relaxed.

    If you are stressed or have ill feeling, skin resistance decreases and the blue LED lights up followed by the red LED along with a deflection of the meter towards the lower side. In short, the red LED and zero meter reading indicate you are stressed, and the green LED and high meter reading indicate you are relaxed. Practise some relaxation technique and observe how much your body is relaxed.




     

    Related Circuits


    Post Comment | 41 Comments



    sowndharya   937 days ago

    super project pa. i need proper guidance for doing this project
    Reply   1 Reply
    Raguvaran   889 days ago

    finished the ckt?? u can do the same with simple 741 op amp with a counter
    Reply  
    Mandar Chendwankar   846 days ago

    what do we call touchpads.......what shud i ask the shopkeeper
    Reply  
    chandu   843 days ago

    How do you people get all those ideas?Plzz... Help me in this regard.
    Reply  
    S.Suriya   842 days ago

    I want to know what is mean touchpad... How those people think like this..help me in this regard
    Reply   2 Replies
    faiz ahmed   819 days ago

    yar bhai is me ye samjh nai araha ke ye working kis tarha kare ga yani ke potentio meter regulate karna pare ga ya aik hi value pe fix karna hai
    Reply  
    amr   657 days ago

    The touch pad can be most easily made by cutting a small square of PCB material and then soldering on a single wire. Alternatively something like a penny glued to a plastic backing will do the job... D
    Reply  
    Rekha   834 days ago

    What is touch pad? how can i get it?
    Reply  
    Bhargavi   834 days ago

    its nice. can you give me some more guidance about this one.
    Reply   1 Reply
    Efy Admin   833 days ago

    What exactly do you want to know?
    Reply   1 Reply
    soumyajit roy   732 days ago

    if VU meter is not available then what kind of or xactly which meter we should use in the place of vu meter????
    Reply  
    vasantha jutla   770 days ago

    how to check the state of person means using dat touch pad. and can i use dis as my college project does it work properly?
    Reply  
    priya   770 days ago

    this is an interesting one for doing a project..i wud like to get some more detailed xplanation regarding the circuit.Admin..u can mail me to priya.voice@gmail.comthank you
    Reply  
    kavitha   755 days ago

    full details abt that project. any drawback about that project
    Reply  
    akshay   745 days ago

    what is a touch pad??any specifications and what to tell to the shopkeeper? plzz do reply fast
    Reply  
    srashti   737 days ago

    i would like to know the applications of this project as i am planning to take it for my major
    Reply  
    soumyajit roy   732 days ago

    i need to know the wattratings for the resistors R1 R2 VR1 VR2..e.t.c
    Reply   1 Reply
    Efy Admin   732 days ago

    All resistors are 1/4W, unless stated otherwise
    Reply   2 Replies
    sanjay   728 days ago

    can you give more applications of this circut?
    Reply  
    Deepti Mishra   543 days ago

    It sounds interesting.I would definitely like to do it as my mini project.It would be very kind of u if u could please send me the exact list of all the components required along with their precise specifications as soon as possible.I would be very thankful to you.
    Reply  
    vani   704 days ago

    nice project... i would like 2 get detailed explanation regarding this project
    Reply  
    krish   602 days ago

    what material should be the touch pads? please reply ASAP as i am doing it for my science project
    Reply  
    vishnucv   595 days ago

    ITS AN AWESM CKT.. ID LOVE TO DO THIS AS MY MINI PROJECT. PLS SEND MORE DETAILS WITH THE COMPONENTS NEEDED TO LEOVCV@GMAIL.COM. ESPECIALLY THE DETAILS ABOUT THE TOUCH PAD
    Reply  
    pooja   568 days ago

    I WANT TO DO THIS PROJECT PLEASE SEND ME THE REQUIRED COMPONENT LIST AND DETAIL PROCEDURE.
    Reply  
    veni   543 days ago

    is this in use now ??? can u send me the detailled values of the components for this project ??? pls soon id is gveni00@gmail.com
    Reply  
    mrunal   522 days ago

    this circuit will work na. pls send me component list & touch pad material
    Reply  
    mrunal   521 days ago

    sir this project is nice. i m doing this project this circuit will work na? can i use multimeter instead of VU meter.
    Reply  
    ramnarayan   467 days ago

    sir i want to made skin responce meter so help me and guide me that instrument where purchage in jaipur
    Reply  
    sujitha   404 days ago

    now the project is used in medical field?
    Reply  
    sohail   400 days ago

    this is an interesting one for doing a project..i wud like to get some more detailed explanation regarding the circuit.Admin..u can mail me to soilshak@ymail.com thank you
    Reply  
    Ranjan   397 days ago

    please give information about the touch pad and its costs
    Reply  
    Bimlendu Shekhar Jha   375 days ago

    kindly inform me about the type of Sensor probe n VU meter Voltmeter need to use in this project.
    Reply  
    pratik jain   375 days ago

    This really awesome ckt .can u please send me all the information like type of componenet used plz sir on joyvanavat@gmail.com
    Reply  
    Bimlendu   372 days ago

    Please let me inform about the sensor probe and VU meter use in this circuit.I am not getting any information regarding these three. please help me out.My mail Id is shekharbimlendu@gmail.com
    Reply  
    neha   352 days ago

    what value at the potentiometer needs to selected for proper working and what are the specifications for vu meter
    Reply  
    Tamilselvan   346 days ago

    what is the use of vu meter......we can replace vu metre by other metre...
    Reply  
    hima bindu   346 days ago

    where do i get vu meter? cannot find it
    Reply  
    Rubina Shaikh   306 days ago

    Sir m done with the ckt...hv connected ammeter in place of VU meter..But not getting the output...Plz let me know about the presetting and adjustment of all the pots..
    Reply  
    mawar berduri   301 days ago

    sir can I know what type of controller that you used for coding of this circuit? can you reply to me as soon as possible please?
    Reply  
    sandhya   137 days ago

    i am not getting proper output...and the VR3 is used for adjusting to glow green led then how we detect relax state....plz give rply...
    Reply  

    Electronics Buzz
     
     
      Magazines
    Electronics for You
    LINUX for You
    Facts for You
    Electronics Bazaar
    Portals
    electronicsforu.com
    efytimes.com
    bpotimes.com
    linuxforu.com
    Directories
    Electronics Annual Guide
    Events
    EFY EXPO
    EFY Awards
    EduTech Expo
    OSIWEEK Expo
    News Verticals
    Electronics
    Infotech
    Linux & Open Source
    Consumer Electronics
    Science & Technology
    BPO
    Educational Institute
    EFY Techcenter
    Kitsnspares.com
     
    © Copyright 2012 EFY Enterprises Pvt. Ltd. All rights reserved.
    Reproduction in whole or in part in any form or medium without written permission is prohibited. Usage of the content from the web site is subjectT etor ms and Conditions