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Analog Input [DRV2667EVM]

Pierre Paul
Prodigy 50 points
Other Parts Discussed in Thread: DRV2667

HI,

I'm currently working on haptic feedback for a project and I need some help. I'd like to drive my piezo actuator with a square wave using DRV2667EVM. I've followed the steps shown on the User's Guide (section 3.5) but I can't figure out why it's not functionning.


I guess something is wrong with my signal, so what signal should I input?

Thanks in advance,

  • 0
    TI__Expert 3280 points

    Hello Pierre,

    Just to be sure, you entered the "Design & Test Modes" mode as described in section 2.5, correct? If not, then please try that.

    If so, can you provide some more details?

    • Frequency and Vpp of your input signal you are providing?
    • Scope shot of your output signal?
    • Specs of your piezo actuator?

    Also, have you tried any of the other modes to see if those work with your piezo? This could indicate if it is a possible issue with the piezo.

  • 0 in reply to Rodney Miranda
    Prodigy 50 points

    Hello Rodney,

    Yes, I did enter mode 7 of "Design & Test Modes".

    Here are what you asked for :

    - Frequency and Vpp of input signal :

    - Scope shot of output signal :

     B1 : 28.8 dB, 50 Vpp, Boost = 30 V

    B4 : 40.7 dB, 200 Vpp, Boost = 105V

    Acutally, the signal is quite noisy but it doesn't appear above.

    I don't think it's due to my piezo actuator because with other modes it's working just fine.

    Also, here a picture of what I'm doing. Perhaps it can be of help. My input signal is given by an Arduino board. 

  • 0 in reply to Pierre Paul
    TI__Expert 8940 points

    Hi, Pierre:

    what's load capacitance of the actuator ?

    Does the DRV2667 chip over-hot during the test?

    Please take a look at the actual VBOOST during the test.

  • 0 in reply to Peter Li79
    Prodigy 50 points

    Hi Peter,

    My bad...It's now working. How stupid I am, I've confused my input terminal with the ground...

    On the other side, the piezo is doing a lot of sound but not that much of vibration...

    That's why I have few questions:

    What frequency is the more suited in order to have the best vibration feedback?

    Also why the piezo actuator (either mine or the one included in the EVM) blows constantly in this mode? even when no input signal is provided

  • 0 in reply to Pierre Paul
    TI__Expert 8940 points

    Hi, Pierre:

    the first question: it usually depends on the actuator characteristics. So, if you can share your actuator spec, I may find the data in it.

     

    the second question:

    "no input signal" means both the IN+ and IN- are connected to ground?

     

  • 0 in reply to Peter Li79
    Prodigy 50 points

    Peter,

    Sorry, I don't have the specs of my actuator, it's a mere piezo disc, 12mm diameter. 

    And yes, no input means both in+ & in- are connected to ground. That only reduced slightly the blast but I can't get rid of it.

    Thanks for your quick replies, I appreciate!

  • 0 in reply to Pierre Paul
    TI__Expert 3280 points

    Pierre,

    What do you mean by the piezo "blows" and/or "blasts"? Like it is damaged or blows air?

    If the inputs are still a/c coupled and you have them tied together, there shouldn't be any differential voltage on the piezo. Can you measure this?

  • 0 in reply to Pierre Paul
    Prodigy 10 points

    Your quetions and the answers really helped.

  • 0 in reply to Rodney Miranda
    Prodigy 50 points

    Hello Rodney,

    I mean it blows air. And I noticed that when I first bought the demo kit.

    Here are the measure that you asked, I've connected the inputs to ground.

    - Scope shot of output signal :

     B1 : 28.8 dB, 50 Vpp, Boost = 30 V

    B4 : 40.7 dB, 200 Vpp, Boost = 105V

     

    Also if you can give me a hint on the reason with my waveforms (frequency between 100-250Hz), the piezo acts more as a buzzer than as a vibrator.

    Best Regards,

  • 0 in reply to Pierre Paul
    TI__Expert 3280 points

    Hello Pierre,

    That looks like a single ended measurement. You will need to look at the differential measurement or look at both of the inputs simultaneously to see if there is any difference.

    In regards to the buzzer vs vibrator, I can think of two things:

    1. The piezo is hitting the edges of the structure containing it (think of a speaker that is being over driven).
      • Try to minimize the gain to see if the noise goes away quickly or if it fades away linearly.
    2. The piezo has some kind of resonance at that frequency that causes noise to occur.
      • Typically you can sweep the piezo across frequency and see how the noise changes.

    Hope this helps.