force sensing resistors pressure sensors foam/sheet/DIY - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th August 2007, 12:31 AM   #1
VvvvvV is offline VvvvvV  United Kingdom
diyAudio Member
 
Join Date: Oct 2003
Location: oxfrd
Default force sensing resistors pressure sensors foam/sheet/DIY

the only force sensing resistor I can get hold of it is the channel aftertouch ribbons that you get in synthesiser keyboards, which are quite big like one meter. I've tried to get information on the commercial small force sensing resistors but digikey is selling them for about $30 each, so for the same price I could get a MIDI keyboard fsr (force sensing resistor) with a leftover keyboard. I've heard there are some foam ones about.

ideally I would like to make a flat thin resistor about 10k, doesn't have to be very exact...perhaps if I get some ordinary polyester and stick conductive Ink in it, when I compress it it should conduct 50% better? That would be perfect!

would love some help!
Attached Images
File Type: jpg 2007-08-07_013934.jpg (91.7 KB, 94 views)
  Reply With Quote
Old 7th August 2007, 01:22 AM   #2
OzMikeH is offline OzMikeH  Australia
diyAudio Member
 
Join Date: Mar 2007
That mylar track sticking out of the keyboard looks more like a capacitance type sensor. you squash foam with a conductive back which changes the capacitance.

I think the resistance would be much higher than you want but you could use antistatic foam with a conductor either side. Perhaps some blank mylar PCB sheet.

It all depends on the ergonomics of the device you are building, a set of electronic scales will have a strain gauge which is a ring of resistors, very small resistance change but you use the differential resistance with a lot of gain to give you a dc signal proportional to force.

If you don't want to design the electronics there are a lot of strain gauge driver boards available that give a 4-20mA current loop output for industrial applications.
  Reply With Quote
Old 7th August 2007, 03:43 AM   #3
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
No, that's probably an fsr. The silver-on-mylar interdigitating conductors are shunted by the conductive foam or a sheet of conductive rubber which changes resistance with compression. A particularly good way of doing it is to use a foam or rubber selected for the desired mechanical response and "feel," and adhering it to the back of a polyester sheet printed with a carbon ink loaded with a rough filler. You want a sheet resistance between 1k and 1k per square with filler in the 5-10 micron range. The sheet is faced against the interdigitating electrodes. The response of this sandwich sensor looks like a linear function of 1/(applied force) so has a much wider resistance swing than the rubber units.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 7th August 2007, 06:46 AM   #4
diyAudio Member
 
I_Forgot's Avatar
 
Join Date: Jan 2005
Location: Phoenix, Az.
The easiest way to make a force sensitive resistor is to sandwich a piece of black antistatic foam of the type used when packaging ICs between a couple metal contacts. As you apply pressure the resistance between the conductors will drop. Some foams are more elastic than others and will last longer with repeated compression/decompression cycles, while others will fall apart pretty quickly.

I_F
  Reply With Quote
Old 7th August 2007, 10:16 AM   #5
VvvvvV is offline VvvvvV  United Kingdom
diyAudio Member
 
Join Date: Oct 2003
Location: oxfrd
thank you for these interesting solutions. I will definitely have to engineer a home made sheet resistor or else find some stuff that can be used as a potentiometer from a moderate finger pressure.

I was going to fix them into the fingertips of a glove although it makes more sense to make a composite substrate of some kind.
  Reply With Quote
Old 8th August 2007, 10:24 AM   #6
VvvvvV is offline VvvvvV  United Kingdom
diyAudio Member
 
Join Date: Oct 2003
Location: oxfrd
for posterity, I should mention that Doepfer has some amazing gear if you live in Germany, including 10K joysticks, but it is a mite harder from abroad.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Speaker damping: Foam or expanding foam akunec Multi-Way 4 11th February 2014 01:14 AM
Foam, thicker foam or Open Cell qguy Subwoofers 4 11th March 2007 07:06 PM
current sensing in series with anode resistors ErikdeBest Tubes / Valves 9 7th March 2007 10:26 AM
Temperature sensors in an amp rtarbell Parts 6 30th July 2006 04:59 AM
ultrasonic sensors sss Everything Else 4 16th May 2006 02:42 PM


New To Site? Need Help?

All times are GMT. The time now is 07:56 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2