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Add external sensors to MetaWearC

ilius_faisalilius_faisal
in Projects, Products & Ideas

I need to add one high precision temp sensor and one GSR with MetaWearC and get raw data using bluetooth. Could Someone please provide me the detail of adding external sensors with the MetaWear board…. I found a project link in mbientlabsaying how to connect an external thermistor to the gpio pins but it is is broken  >> http://projects.mbientlab.com/me...

details.Could anyone help me by giving me the details.

Comments

  • EricEric
    There really isn't anything other than connecting your external sensors to the GPIO pins.  You may need to add additional components depending on the sensor's electrical specifications.

    Which components exactly are you looking to connect?
  • ilius_faisalilius_faisal

    I need to connect GSR and temp sensors. So my question is:

    1. can I add two external sensors (GSR and Temp) with one board?
    2. How to configure those sensors to get the raw data via Bluetooth?
  • EricEric
    Yes, i know you want GSR and temp.  Please link to the specific sensors so we can see if they are compatible.

    The answers to your questions depends on the specifications of your components.  In general, yes, you should be able to connect both sensors but again, we'd have to see the datasheets.  Interacting with your external sensors is done with the GPIO pins or SPI/I2C bridge.
  • ilius_faisalilius_faisal
    Thanks, I connected the sensors and able to communicate.
    But Now My question is how to get the resistance values of the external sensors...
    Could you please tell me how to acquire the raw data from those sensors...
  • EricEric
    edited February 2018

    Isn't that type of information detailed in your sensors' spec sheets (which you have yet to link to)? Furthermore, you haven't mentioned how the sensors are connected to the board so I have no idea how you are using the external sensors.

    Please provide more details about your setup and post which platform you are developing on.

  • ilius_faisalilius_faisal

    I am using a simple 10K Thermistor. The thermistor is hooked up the GPIO0 and the 3V pin on the MetaSensor board. a 10K bias resistor is hooked up in series between GPIO1 and GPIO0.
    In the tutorial, it is said that "To measure the temperature, we measure the current resistance of the thermistor (the variable resistor)."
    I am using sample metawear android app to acquire the Data. But I am not able to find out any API which will give me resistance value of the external thermistor. Could you please help me in this matter and instruct me so that I can make it work by acquiring the raw data I want from the sensors.

  • EricEric

    You can't directly retrieve the resistance. You can instead read the voltage at GPIO 0 and use that to calculate the thermistor's resistance:
    https://mbientlab.com/androiddocs/latest/gpio.html#analog-data

    Is there a reason why you are using your own thermistor rather than the one included on the board?

  • ilius_faisalilius_faisal

    Ya, I am using my thermistor to measure the change in Skin temperature. The sensor should in the contact of the skin.

  • ilius_faisalilius_faisal

    Hello, sample metawear android app I am getting the Temperature value in Celsius directly using an external thermistor. But could you please explain to me how the temperature value is calculated or converted? Could you please direct me to the android code or library which is responsible for this calculation or conversion table. I need to know the API used in handling the calculation and conversion.

  • EricEric

    @Eric said:
    You can't directly retrieve the resistance. You can instead read the voltage at GPIO 0 and use that to calculate the thermistor's resistance:
    https://mbientlab.com/androiddocs/latest/gpio.html#analog-data

    Is there a reason why you are using your own thermistor rather than the one included on the board?

    Your thermistor's spec sheet should provide a table or formula that converts the analog signal into temperature.

  • ilius_faisalilius_faisal
    edited March 2018

    @Eric said:

    @Eric said:
    You can't directly retrieve the resistance. You can instead read the voltage at GPIO 0 and use that to calculate the thermistor's resistance:
    https://mbientlab.com/androiddocs/latest/gpio.html#analog-data

    Is there a reason why you are using your own thermistor rather than the one included on the board?

    Your thermistor's spec sheet should provide a table or formula that converts the analog signal into temperature.

    I got your point. But every time you are getting me wrong.
    I am not asking that. I mentioned several times that I am using sample metawear android app and I am getting the Temperature value in Celsius directly using an external thermistor. But I am not able to find the temperature calculation or conversion in the codebase. Could you please direct me to the code or library which is responsible for this calculation or conversion table. Like how the app is getting this temperature value in Celsius?? there should be any math inside. Please help me to find this if you can.

  • EricEric

    All temperature measurements are handled by the board/firmware and simply forwarded to the host device. None of the code in the SDK or sample app performs any temperature calculations.

  • AmmarAmmar

    Hi,
    We are curios about 2 things:-

    1. We need to add GPS location tracker via i2c line. It is possible?
      Or do MMR module come together with accurate location service which can be derive from BLE ?

    2. How far is the range for BLE and how many can be connected at instantaneous time?

    Thank you

  • LauraLaura
    1. It is not possible unless you can find a 3v compliant part that can run on our small battery. typically gps modules are pretty power hungry and cannot be powered by our system.
    2. ble is around 30m. # of connections is typically 3 but we and some users have been able to get 10+ simultaneous connections on linux systems.
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