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trying to measure both the level and flow of plastic pellets — Parallax Forums

trying to measure both the level and flow of plastic pellets

laser-vectorlaser-vector Posts: 118
edited 2012-10-11 15:33 in Accessories
Hi,

I was wondering if anyone might have some suggestions on how to measure both the level of plastic pellets being dumped into a container and when they are flowing through a tube??

I'm not at all sure how to measure their level in the container at this moment but I am thinking that using beams of light would be best to measure when they are flowing through tubes. I'm sorry if this sounds very vauge but the project is new. I'm not fully sure of all my available options yet and am still doing research.

The material im trying to measure ranges from very shinny smooth textures to dull and dusty material.
The tubing is about 2" in diameter and the material ranges from little 0.125" balls to .375" chopped up crud..

Any ideas, shared experience or suggestions would be great as I have just been given the OK to go ahead with prototying and i need to get some sensors to experiment with soon

Thanks!

Comments

  • W9GFOW9GFO Posts: 4,010
    edited 2012-10-09 20:22
    Making an extruder?

    If the container is large enough I think an ultrasonic sensor would work for measuring the level. For the presence of pellets in a tube - an IR sensor seems appropriate.
  • SRLMSRLM Posts: 5,045
    edited 2012-10-09 21:35
    What about this? http://www.parallax.com/Store/Sensors/ColorLight/tabid/175/CategoryID/50/List/0/SortField/0/Level/a/ProductID/566/Default.aspx
  • prof_brainoprof_braino Posts: 4,313
    edited 2012-10-10 04:43
    What volume and rate are you looking for?
    How big are the pellets, how big is the tube, how big is the reservoir?

    I've seen a really cool method where chunks are carried by entrainment in an air stream, moved a lot of material a long way fast!
  • Beau SchwabeBeau Schwabe Posts: 6,557
    edited 2012-10-10 09:24
    Depending on your answers to prof_braino ... and based on the Triboelectric effect, It may be possible to get a voltage reading proportional to the flow and volume.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-10 10:15
    W9GFO wrote:
    If the container is large enough I think an ultrasonic sensor would work for measuring the level.
    If you go this route, be sure to take the median of several readings. In an industrial environment, mechanical noise is the enemy of ultrasonics and can lead to spurious, low distance readings.
    SRLM wrote:
    What about this? http://www.parallax.com/Store/Sensor...6/Default.aspx
    The TSL1401 might be good for detecting flow, by using a backlight and measuring and summing the overall shadow area over time as the chips fall in front of it. If the flow is high enough, though, that the chips overlap front-to-back, you will get erroneously low readings.

    -Phil
  • Scott4Scott4 Posts: 45
    edited 2012-10-10 10:20
    Considering the variability of the pellets, would weight be appropriate? In a previous life we had to limit the mixture to less than a certain % of reground plastic to virgin pellets BY WEIGHT. Volume was not reliable. -Scott
  • SRLMSRLM Posts: 5,045
    edited 2012-10-10 21:01
    Phil Pilgrim (PhiPi) wrote: »
    The TSL1401 might be good for detecting flow, by using a backlight and measuring and summing the overall shadow area over time as the chips fall in front of it. If the flow is high enough, though, that the chips overlap front-to-back, you will get erroneously low readings.

    -Phil

    I was thinking more of an optical flow method, with the axis of the sensor parallel to the flow of the particles. It's reminiscent of a plane (with such a camera) tracking the motion of the ground and estimating ground speed.
  • RS_JimRS_Jim Posts: 1,762
    edited 2012-10-11 07:04
    Parallax product 29131 etape sensor could measure the depth and flow in tube by one of the optical methods mentioned.
    Jim
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-11 11:38
    SRLM wrote:
    I was thinking more of an optical flow method, with the axis of the sensor parallel to the flow of the particles. It's reminiscent of a plane (with such a camera) tracking the motion of the ground and estimating ground speed.
    I was assuming the pellets were gravity-fed, hence falling at a known speed past a given point. Placing the linescan axis horizontally would provide info about volume/sec.

    -Phil
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-10-11 15:33
    Just a thought about measuring pellet flow: any chance you could allow the flow stream to impinge upon something like a thin metal plate and have a sound sensor count the number of hits? NASA used something like that in some of its first rockets to measure micrometeorites and I know you could pour a hand full of sand over the sounding plate and watch the device count like crazy. I think adjustments are made for poisson statistics, or whatever they're called. I wouldn't have dared mention it but since Beau brought up the thing about triboelectricity.... :)
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