Amplify bend sensor

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I need to measure the intensity at which people blow to a screen. I am using a bend sensor with a sheet of paper attached to it to detect air movement (the paper acts like a sail). Here's the sensor:

In my tests I have been blowing directly into the sensor (with the sheet of paper) and it works fine. But in its final form, I need people to blow into a screen and have the sensor hidden on the side, underneath a specially designed frame. So actually the air will be blown at the screen and then flow to the side. As a result, the air movement intensity is much lower. Because of this, I will only use a very small segment of the sensor range and I need to find a way to amplify its signal so that I can have better precision.

Having found an OpAmp which seemed appropriate (Op-Amp) I decided to buy it, but being totally dumb with electronics (I'm trying to learn, honest!) I didn't manage to make it work and I'm not even sure it would.

So, I ask your help: how to amplify the signal of my sensor in order to be able to use only a part of its full range and still get decent sensibility?

Thanks in advance,
Nuno

2

hello,

i've never worked with bend sensors, but i'm a little afraid, that amplifying an analog signal to pump up sensitivity might not be ideal. if the signal you're getting now is not distinct enough you'll probably might just end up amplifying unwanted noise... but i don't want to discourage you, as i said i've never worked with bend sensors.

maybe you can solve your problem mechanically, by adding a lever to your sail/sensor design?
you could also try using a temp sensor , or a classical windmill (plus a photo-diode and LED) to get your information.

sorry that i can't help you with the op amp.

kuk

3

I'm not sure what would be better - just multiplying the values in the Arduino or having a proper amplifier.

Try it with the Arduino first. Its simpler and more flexible.
You want something like this to double the sensitivity:

in = analogRead(port);
in *= 2;
if (in > 1024)
{
  in = 1024;
}
4

Hi kuk, thanks for the suggestions.

Hi Cheater, you know what, that makes a lot of sense and I believe didn't try it. Thanks!!! I wil try it and post my results here soon.

Nuno