# Simple Thermal Project

Discussion in 'The Projects Forum' started by mustafagtgt, Dec 2, 2009.

1. ### mustafagtgt Thread Starter New Member

Dec 2, 2009
2
0
Hi, I am new this thread and I would like some help and advice on how I can constuct a simple thermal device.

I am thinking of using a thermistor which is a type of resistor which varies with tempreture. I would like to know How I can impliment this resistor affectivly in a working circuit with other neccesary components. My main aim is to contrust a device that reacts to a shift in Room tempreture.

General temperature related to human comfort can vary from 20.0 Celsius to 25.0 Celsius. I will programme the device to indicate when the temperature has risen above 26.0 Celsius allowing some flexibility and also I when the temperature has fallen below 15.0 Celsius.
A Red LED will turn on when Tempreture has risen above 26 Celsius
A Blue light will turn on when Tepreture has fallen blow 15 Celcius
How can I create this?
Thank you

2. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
Is this a homework problem?
Can you use an LM35 instead of a thermistor?

3. ### mustafagtgt Thread Starter New Member

Dec 2, 2009
2
0
What exactly is a LM35?

I am actually doing a Project at College and for my Project I chose to do make a a sensor which turns a Red LED or Blue LED depending on the room temperature...

4. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Then this is a homework assignment, and should be in the Homework Help forum.

An LM35 is a temperature sensor that is available in a TO-92 plastic case. These are sometimes called "three legged critters".

If you supply it a certain voltage level, it will output a voltage that can be read in °C.

You could use that output in conjunction (with the assistance of) a "window comparator" circuit to light your LEDs.

Google is your friend.

5. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
I provided a link to the datasheet...

6. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
Why dont you just borrow my wife. She doesn't need an electronic circuit to tell if the house temperature is less than 69.9degF

7. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
1,305
Hmmm, I'm gussing she might be equipped with the "high dB audible alarm option"?

8. ### logans-electronics Member

Sep 1, 2009
36
0
This will get you started. I used in an inverting op amp to vary the fan speed based on temp....I also added a 16 led array for a visual indicator. The FET has a 4 volt drop to the fan. I had to build this backwards. Find your VSAT- the GOS drop of 4 volts. I had to play around with the gain structure to get what I needed....Hope that it atleast gives you some start...

Mesure your resistance at the tempurature values you need....sounds weird but I placed my thermistor in a curling iron on high and turned it off(attach a thermometer also)...it will slowly cool down enough where you can get half way decent measurements. This is how I determined my gain and RI and RF resistors.

File size:
50 KB
Views:
19