Replies to This Discussion

Permalink Reply by Kathy Moseler on January 28, 2013 at 11:13am

Hi,

I attached the datasheet because I am not sure if you have it.  Read it over if you haven't already.

It is probably measuring the temperature correctly so you have to figure out what could be making the temperature go up.  It could be where it is placed.  I cannot give advice without having a lot more information about what you are doing with it and how you hooked it up.

Start with the datasheet and then lets go from there...

Attachments:

• lm35.pdf, 342 KB

Permalink Reply by selvakumar on January 31, 2013 at 7:33am

i use the detail given in the following attached file...the temperature value not stable..and also IC heated..what is the reason? any other interface circuit method available

Attachments:

• interface LM35.pdf, 740 KB

Permalink Reply by Kathy Moseler on January 31, 2013 at 9:28am

It's good that you are using a proven circuit configuration.  This helps narrow down the possibilities.  It would be helpful if you stated the temperature readings you are getting over time.  Example, at power on, one second later, two seconds later, etc.  Also, if the IC is getting too hot to touch it, there is definitely something wrong and you should immediately disconnect the power. 

Here is a partial list of possibilities from most likely to least likely:

1) Something is connected incorrectly.  Do you have a multimeter?  It is best to check the connections with a multi-meter on the ohms setting.  If you don't know how, find a YouTube tutorial.  If you are an expert, you can probably find the mistake visually.

2) Any possibility the power input voltage is incorrect?  Double check it with the multi-meter on the DC volts setting. (Again, YouTube if you don't know how).

3) Incorrect component value populated.  It is easy to mis-read the component value.  Example, 10 ohms or 100 ohms instead of 10K ohms.

4-100: A bunch of reasons I forgot about.

101) Faulty component.  Extremely unlikely unless you actually burned it out in the process of monkeying around.  The way to check it is to isolate each component one at a time and measure them with a meter.  E.g., measure your potentiometer in each setting (lowest and highest), hook up the temp sensor in a basic circuit without the Arduino.  If it works on its own, it will work in the circuit.  If it still doesn't, there is something else wrong.

The reason I put Faulty Component as # 101 is in my experience it is the least likely problem with a new circuit.  Usually the problem is caused by something to do with the wiring.

Have you used a breadboard before?  If not, don't assume you know how it works.  Use some small wires and a meter to figure out where the internal breadboard connections go.  You could be assuming something about the breadboard that is wrong.

Permalink Reply by selvakumar on February 1, 2013 at 7:42am

thank u sir.i will check and tell the result.