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Brain v2 with Interlink Electronics FSR 408

Hello,

I'm new to the Livid Instrument Builder, just received the kit yesterday.


The plan is to build an instrument using Interlink Electronics FSR 408 sensors

http://www.interlinkelectronics.com/FSR408.php


I quickly tried one last night (I"ll use 61 of those in total)
wired 1 FSR 408 
one tab to the +Voltage 
the other tab to ID 01
With Brain Configure I only enabled Analaog ID 01, 
sent configuration to the brain

but I couldn't get a decent response out of it,
I tested with all 6 fsr modes.
I couldn't get fast rolls to register, I had to wait a second between strokes.

Anything special I should do ?


Reading through the wiki I just found :
Unused analog pin headers need to be physically grounded using our header ground boards supplied with each Bus Board. If unused analog connections are left open you will have a noisy stream of MIDI data from the open pins! Grounding unused headers are easy by just plugging in the female socket of the ground board making sure to line up the arrow designating pin 1 marked on the BusBoard header to the white square marked on pin 1 of the grounding board.

Is that still the case? Could this be the issue?

Datasheet for the FSR sensor is available here :
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Comments

  • Ok, thanks for the explanation.


    Would the diodes present in the starter kit work?
    Or should I buy specific resistors (The brain jr example mentions 10k Ohm resistor)
    Sorry for the stupid questions
  • edited April 2015

    Once again thank you for your answer.

    Sorry I totally missed the "Pull-Down Resistor Value" part in your first reply.

    Bought some 10k-ohm resistors earlier and the sensors are already working quite well now.
    Will buy some 100k-ohm and 1M-ohm to try

    Out of curiosity, what would happen if I removed the Bus Board from my Brain V2 since I mostly need anlaog 
    It would make the board smaller, but would it still work ?
  • Does it matter if a sensor is connected to AV+ and AV- of say A1

    but connected to a wiper (analog signal) on A3 ?

    Trying to find out how messy the cabling is gonna get

    What's the easiest way to :
    - split AV+ in 8
    - split AV- in 8

  • Further testing went on but the Brain v2 doesn't seem to trigger fast enough.

    Striking the interlink Electronics FSR 408 sensors with a stick, it doesn't seem to get a reading,
    it works fine using my fingers though.

    I've used various resistors, from 10k to 1M.
    If I hold the stick down after hitting the sensor, I do get a reading, but not with a normal speed strike,
    playing like that wouln't work.
     
    Is there a way to get more advanced settings for the FSR sensor type ?
  • My brain is on order, but I hope to also figure this out for myself too.

    It might be you need a piece of plastic on top of your FSR to spread the hit area when you hit it with the tip of a drumstick.

    Alternatemode.com sells a image fsr that's made to be hit with a drumstick. 
    http://www.alternatemode.com/triggers/altzone.shtml

  • Any official word?

  • Thank you Moon,

    I'll try and make more tests with FSR attached firmly on the surface and in potentiometer mode.
    I don't know if it is sensibility related though, I did hit the sensor pretty hard, with various elements in between the FSR and the drumstick and none of the hits were detected unless I kept the stick down to lengthen contact/pressure time.

    Reading through this paper, contact time between a drumstick and a head seems to be between 3ms to 6ms
  • Paia has a "Drum Sensor Processing Amplifer" schematic and kit.
    http://www.paia.com/ProdArticles/drumsens.htm

    The diode, cap, and resistor being the peak detector

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