Pressure sensor recommendation for amputee

Comments

• Phil Pilgrim (PhiPi) Posts: 23,514

  2018-12-23 18:18

  Google insole pressure sensor.
  
  -Phil
• Jonathan Posts: 1,023

  2018-12-23 18:38

  Thanks Phil. When he gets back to being able to wear a shoe, that looks like an interesting option. For now though I need something that I can attach to his bandage/brace.
• Beau Schwabe Posts: 6,547

  2018-12-23 20:22

  In prosthetics, my experience with using TeckScan sensors is that the sensors delaminated very easily with sheer stress inside of the shoe. Also the slightest kink or fold in the sensor causes a false reading or caused the sensor to be inoperable.
  
  While in prosthetics, we developed our own sensor that would last orders of magnitude longer which consisted of nothing more than a printed circuit coil on a flexible circuit board. The sensor was constructed using a metal foil separated from the coil with a neoprene foam barrier. At the time (1995) we contacted a company that makes flexible printer ribbon cable to make the flexible circuit board. Reading the coil was done in the same way a PI metal detector works. Pulse the coil, and then measure the energy response. This was done with a current mirror charging a cap, and then an ADC reading the cap before discharging the cap. This method is faster than allowing the coil to resonate and then measure/count then number of pulses withing a known amount of time. All of my links on the Parallax sight and the OBEX seem to be broken, but I had a Propeller version using the PI method in the OBEX. Perhaps someone can dig it up.
  
  https://patents.google.com/patent/US6500210B1/en?inventor=Schwabe&oq=Schwabe
  
• Publison Posts: 12,366

  2018-12-23 21:04

  Beau,
  This may be the file:
  
  http://obex.parallax.com/object/780
  
  All your files can be found in OBEX under the author "Parallax Inc".
• Beau Schwabe Posts: 6,547

  2018-12-23 21:31

  Publison,
  
  Yes, I think that is the file... it uses the system clock to perform the ADC, but the original circuit used in the referenced patent above just read from a discrete ADC.
  
  "All your files can be found in OBEX under the author "Parallax Inc"" - Perhaps, but the links to all of the web content are all broken. Thanks anyway.
  
  
• Jonathan Posts: 1,023

  2018-12-23 21:38

  Thanks Beau and Publison. I just spoke to his wife and at this point I don't think we need anything that fancy. When we get to him re-learning to walk I think we will. Right now the Doc says no weight at all. So a simple switch would even work for starters. I have been noodling around but can't seem to find the right search term for a simple pressure switch encapsulated in a little bubble or something like that.
• Publison Posts: 12,366

  2018-12-23 22:06

  Beau Schwabe wrote: »

  Publison,
  
  Perhaps, but the links to all of the web content are all broken. Thanks anyway.
  

  
  I hate that I do not have permission to fix links. It bugs me also.
• T Chap Posts: 4,198

  2018-12-24 04:18

  I recently experimented with a load cell and HX711 breakout board. This was very easy to set up and measure pressure. You could have something running in a few hours. You can set a threshold for a certain pressure. A piezo switch is an alternative.
• potatohead Posts: 10,253

  2018-12-24 04:34

  https://goo.gl/images/fw4vBN
  
  One of those may work. Just attach something to the lever that is big.
  
  
• kwinn Posts: 8,697

  2018-12-24 18:02

  Google metal dome switches. One or more switches in parallel should do what you need.