# LM35 connected to op-amp

Discussion in 'Homework Help' started by aab09, Dec 22, 2014.

1. ### aab09 Thread Starter New Member

Dec 12, 2014
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Hi
I need your help. My project is to design sensor that connected to op-amp.
temperature range from 35°C – 45°C, and ADC range 0 – 3.3V.

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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So what have you already done?

3. ### aab09 Thread Starter New Member

Dec 12, 2014
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actually, nothing
I need some hints to begin designing

4. ### MikeML AAC Fanatic!

Oct 2, 2009
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Well, I would start by reading the data sheet for the LM35

5. ### Dodgydave AAC Fanatic!

Jun 22, 2012
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The sensor gives out 10mV per degC, 35C to 45C thats a voltage output of 350mV to 450mV,

6. ### Alec_t AAC Fanatic!

Sep 17, 2013
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.... so you need to amplify and offset those mV to get 0-3.3V (ideally). Read up on opamp theory.

7. ### aab09 Thread Starter New Member

Dec 12, 2014
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I asked the doctor about it he tell me to get output voltage of opamp=0 when T=35, output voltage of opamp=3.3 when T=45

8. ### MikeML AAC Fanatic!

Oct 2, 2009
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We, instead just giving you the answer, in which case you learn nothing, are waiting for you to show some initiative and suggest a solution...

btw- I am a retired doctor (PhD). If you were my student, I would fail you if I learned that you just copied a solution that someone handed to you.

Last edited: Dec 22, 2014
9. ### ScottWang Moderator

Aug 23, 2012
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So now you should figure out how a op amp to do the amplifying as inverting and non-inverting, and then draw the circuit and attach it here.

10. ### Wendy Moderator

Mar 24, 2008
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You will note that everyone assumes this is home work, which means it gets treated differently. Make a serious attempt to solve the problem, draw a schematic you think might work, and you will go further. The more input you give the more hints toward solutions you will get, and the more you will learn.