MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

FSR Linearization circuit question
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author FSR Linearization circuit question
j450nn014n
Hi;

I'm trying to build an FSR linearization circuit that I found on http://www.openmusiclabs.com/learning/sensors/fsr/index.html And it is just not working and I don't know what I'm not understanding. I do know to power the op amp. I tried this with a LM324N LM358 but I get no voltage out at the end.

Anyone got any examples of simple circuits like this? I just want to linearize the resistance on the FSR so it doesn't drop so fast.

Thanks, in advance, for any advice or commisserations.

guest
what voltages are you using to power the opamp? what are the voltages on all the pins of the opamp? which fsr are you using? if the output is stuck around 1V and not moving much, you could try a larger gain control resistor, maybe 100k.
j450nn014n
guest wrote:
what voltages are you using to power the opamp? what are the voltages on all the pins of the opamp? which fsr are you using? if the output is stuck around 1V and not moving much, you could try a larger gain control resistor, maybe 100k.


I've got 15V going into the Vcc and Vss. Tried it with 9 as well. The op-amp data sheet said it could handle something like 3-20V. I'll try 100k on the gain.

I woke up from a dream last night and thought... hmmm... what do I do with the ground on my power supply? Where do I hook that up? I hope that that's the problem. I did not connect my ground from the power supply for the op amp to the ground for the signal going into the op-amp. I read somewhere that there needs to be a common ground, but that wasn't made clear in any instructions I've seen to date. Since they were separate power supplies for the signal and the powering the op-amp, I reasonably assumed they were not on the same ground. We'll see. Thanks for the suggestion.
guest
yes, the grounds need to be connected. this is most likely the issue.
j450nn014n
guest wrote:
yes, the grounds need to be connected. this is most likely the issue.


ZOMFG... it was your tutorial I was using! i just realized. :P

OK, it works now that I got the ground right. I'll cite your tutorial on linearizing FSRs when I'm write up the final project for publication, though I'm probably going to use linear hall effect sensors, magnets and springs in the final version.

Funny thing is that I've not found a sufficiently remedial tutorial to explain how to hook up op amps to Vcc and Vss (and the variations). But that's an endemic problem for everyone who creates learning tools. Ray Wilson was the best I'd ever seen...

Thanks for the confirmation.
MUFF WIGGLER Forum Index -> Music Tech DIY  
Page 1 of 1
Powered by phpBB © phpBB Group