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DRV2605: Help on a school STEM project

Kevin Murray
Prodigy 20 points
Part Number: DRV2605

I need help to help my 8th grader to develop a prototype for his upcoming STEM project.  The idea is to put a small ultrasonic sensor on a cane to detect a tripping hazard a few feet away and set off a haptic feedback device in the cane handle to warn a person with vision and hearing handicaps.  I was looking at the DRV2605 as a device to drive a small Linear Resonance Actuator (LRA) or Eccentric Rotating Mass(ERM) device.  Not sure how to connect a ultrasonic device (e.g. Arduino HC-SR04 Ranging Detector Mod Distance Sensor, others) to drive the DVR2605 (or similar).  My first question would be is there anyone interested in helping guide us, possibly answer a series of developing questions?  Is there a better forum to post this to?

  • 0
    TI__Guru* 84915 points

    Hi, Kevin,

    Welcome to E2E and thank you for your interest in our products!

    We can help you with all the questions about our haptics drivers. However, we will need of additional information in order to have a better approach to your application.

    Our haptics drivers are not capable to handle ultrasonic frequencies. Could you describe some characteristics of the ultrasonic sensor output? Should the haptics driver output be proportional to the sensor output? Or is it independent of the sensor output result? Do you have a block diagram that could describe your application?

    Any other information you could provide will be appreciated.

    Have a good day!

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 20 points

    Thank you so much for the quick response.  I have attached a PDF with a simple prototype concept of a cane with ultrasonic sensor at the tip and  haptic feedback in the handle to warn a vision/hearing handicapped person of an object a few ft away.  A block diagram is also included as best I can tell for the required components.

    I as best I can tell from limited research into the HC-SR04 Ultrasonic Distance Sensor, it takes a trigger signal (On pulse) and transmits an ultrasonic pulse.  If it detects an echo, it sends a pulse with a duration based on the delay for the echo.   I guess I would need a small microprocessor like a Arduino or Raspberry Pi to receive the duration pulse and calculate the distance, then send a signal to the  Haptic Driver, e.g. a SparkFun (PID 14538) Haptic Motor Driver - DRV2605L or Adafruit DRV2605L Haptic Controller Breakout board to fire the LRA or ERM haptic device. 

    The simplest concept is if the processor determines an object is within a given distance, say 3ft, then the haptic device vibrates for a  second or two (tune-able on a breadboard perhaps).  A more sophisticated system would use the distance and vibrate the haptic device at a freq inversly proportional to the distance.  I do not know what values to use here so I would guess and say 60Hz for an object at 3ft, rising to perhaps 1kHz as the distance shrinks.  Again, maybe these parameters are tune-able on a breadboard.

    What do you think?  Any recommendations on a simple microprocessor?  The LRA devices I've seen all seem to be DC and vibrate at a single resonance freq so perhaps making it vibrate inversely proportional to distance won't work.

    Thanks!

    STEM concept.pdf

  • 0 in reply to Kevin Murray
    TI__Guru* 84915 points

    Hi, Kevin,

    Thank you for providing the details about your project. It is clear to me now.

    Regarding the microprocessor, unfortunately we cannot recommend any part since these devices don't belong to our group. You would need to contact the processors group ( https://e2e.ti.com/support/processors/f/791 ) to have a better opinion.

    Regarding the haptics driver, I could recommend some devices from the DRV26xx family as you correctly mentioned. These devices are not too complicated to configure (we can provide some guidance if necessary), but you have some options here:

    - All the devices from the DRV26xx family support analog/PWM input. So, you can create different effects based on the PWM duty cycle or the amplitude of the analog signal.

    - The DRV26x4 devices support integrated RAM for customized waveforms. You may create your own signals with amplitude/time pairs. You may use them depending of the effect that you require.

    - The DRV26x5 devices support integrated ROM with predefined waveforms. There's a 128 effects list and you can use them individually or in sequence. This is a good option if you are looking to control the actuator via I2C.

    I hope this helps you. Please let me know if you have additional questions or comments on this.

    Best regards,
    Luis Fernando Rodríguez S.