This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

TLV3404: Piezo element // 2 stage op-amp design

Part Number: TLV3404

Hi,

We are working an a design with a piezo element. This piezo element (long cable) generate an output when it is triggered (e.g. by a car driving over it). The piezo output has to be digitalized such that it can server as an interrupt to a processor. For this I want to use 2 opamps.

The first opamp amplifies the piezo signal and the second opamp is a comparator. The output of the 2nd opamp is fed into a processor. For the opamp design the following is considered

  • Piezo Sensor cable:
    • Ouput varies between 20 and 50 mVs
  • Opamp low power - TLV3404 (low power opamp is key as it should be possible to run on a battery)

As the piezo cable is a separate sensor I am not sure how the input bias current path could run. Have a quick sketch drawn below. As I am not an opamp designer I hope you can give me some guidance or tips how I could make this design work

Thanks a lot!

  • In reply to kai klaas69:

    Hi Kai,

    Not using the OPA348 for the simple reason that it does not come in a DIP package. I am only used to work with breadboard before creating a PCB protoboard.

    (maybe silly question but are there other ways to test non-DIP packages?)

    The TLC272 comes in a PDIP package so that is one I can use to test.

    Thanks

    Jeroen

  • In reply to Jeroen van Bussel:

    Hi Jeroen,

    to use SMD parts on a breadboard solder very very thin copper wires directly to the SMD pins. Use lots of flux, turn down the temperature of soldering iron to 300°C and touch the SMD pins with the iron only for a very short time. Then solder the other ends of these very very thin wires directly to the resistor wires and capacitor wires the SMD pins shall be connected to.

    There are also adapter boards available which carry the SMD part and lead the SMD signals to solder terminals:

    www.breadboard-adapters.com/.../SOIC8-adapter.html

    Kai
  • In reply to kai klaas69:

    I think I prefer the adapter boards // just ordered a bunch of them. thanks for this info.
  • In reply to Jeroen van Bussel:

    Received the adapters and got the circuit working with the OPA348 and the TLV3012. The detection of the piezo signal goes very well.Have connected the output directly to a micro processor and signal is received.

    However there is one issue which I have not found a solution for. After measuring on the oscilloscoop I found out that when the output (comparator) goes from LOW to HIGH the first 50 usecs the signal bounces a couple of times.Not sure what the best measurements are to eliminate this?

  • In reply to Jeroen van Bussel:

    Hi Jeroen,

    you could add some hysteresis:

    Kai

  • In reply to kai klaas69:

    Thanks Kai, that did the job! No more swing in the output

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.