Can't see HB100 output

Discussion in 'The Projects Forum' started by ord6, Jul 17, 2014.

  1. ord6

    Thread Starter New Member

    Jan 24, 2014
    9
    0
    Hello,

    I'm using the HB100 speed sensor for a project (http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Application_Note.pdf).

    To get things started, I applied 5V to the 5V pin and connected to ground.

    When connecting the IF output to the scope all I can see is a noisy signal (image attached), and not a signal that is presented in the video (bottom signal) in the following link:
    http://www.limpkin.fr/index.php?pos...lectronics-for-a-$7-USD-doppler-motion-sensor.

    Can someone help me to see a nice signal in the scope like there is in the video?

    Thanks.
     
    Last edited: Jul 17, 2014
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Did you build and test the amplifier and filter circuit the author recommended?
     
  3. shakilabanu

    Member

    Jul 8, 2014
    44
    2
    you need to filter out the signal. Use a low pass filter as mentioned in the data sheet.
     
  4. ord6

    Thread Starter New Member

    Jan 24, 2014
    9
    0
    I wanted to see if the sensor works before trying the circuit.

    I know that I need to filter and amplify the signal and I designed the circuit that I want to use but before that I wanted to check if the sensor works so I'm trying to get the same output as the author in the link above (the bottom signal is suppose to be the IF output of the sensor)

    Is it possible that the sensor is nonfunctional? or maybe the scope I'm using can't read this low signal (micro volts)?

    Thanks.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    On the web page you cited, the author, limpkin wrote:
    "The HB100 outputs a low level voltage (few uV) whose frequency represents the speed at which an object is moving towards or away from the sensor. The output can be very noisy, so in addition to amplifying the signal, we need to filter out frequencies that don't match what we expect from ordinary objects."

    The emphasis is by the author.

    It looks like you are going to need both the amplification and the filtration if you want to see the signal.
     
  6. ord6

    Thread Starter New Member

    Jan 24, 2014
    9
    0
    I asked the author and he said that the lower signal is IF, straight from the sensor, without any processing.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    Did you put a resistor of 12K to the output of the IF, as shown in the schematics?

    Bertus
     
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