temperature sensor - help me with this circuit

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rainyleow

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hi...can someone who is kind-hearted help me to come out with this circuit?

A circuit that is able to show the temperature levels of human body is to be designed.
Basic circuit function:
Able to measure human body and indicates the temperature levels by using LEDs.
1. When the temperature is 37 o C, first LED will be on.
2. When the temperature is 38 o C, first LED will be off, and second LED will be
on.
3. If the temperature is 39 o C and above, the first and second LED will be off and
the third LED will be on. Besides that, a fan will be moving.
 

temperature sensor using pic18f4520

u need a microcontroller for that

do some search on google
 

pt100 with pic18f4520

can also be done with 4 op amps and some logic gates...
 

Re: temperature sensor

hameeds01 said:
u need a microcontroller for that

do some search on google
Click to expand...

Sure for simplifying the design but you can use a PT100 with simple logic function and some comparators.
 

Re: temperature sensor

thanks for reply...u all are so kind.
i know i need a microcontroller ,however i don't know what type of microcontroller i should use. Actually i have another one hardware to do which is using PIC18F4520.Then for this hardware is it suitable to use back the same one?
 

Re: temperature sensor



PIC18F4520 for such a simple application ?
Use the 16F84.
 

temperature sensor

haha...
But then if wanna to use PIC,don't we have to learn to program it?
If yes, why not i just use back for the same one?
 

Re: temperature sensor

rainyleow said:
haha...
But then if wanna to use PIC,don't we have to learn to program it?
If yes, why not i just use back for the same one?
Click to expand...

Frankly let me tel you that the using of µC in such application is a waste of money since we can do it by simple electronic circuit.

Let say that the purpuse of your application is to study microcontroller. You have to learn circuits design and microcontroller programming. And the better way is to start with simple microcontrollers since their architecture and the function that they have are simple to understand.
 

temperature sensor

the simple for u is hard for me..
 

temperature sensor

ha...nothing...mean i am still young to try~
thank you very much...although i don't know french...but i try translate it.
 

hi rainyleow..did you manage to do up the circuit successfully?
 

hi
u work with small range of temperature 37C°,38C°,39C° for that range u can use
PTC,NTC thermistor or can use LM35 compelete temp sensor ......
if u use LM35 u will get about ..(0.37v at 37C°)..(0.38v at 38C°)..(0.39v at 39C°)
in simple way make LM35 drive 3 comparator ....
setting for first at (0.37v) ...second at (0.38v)..third at (0.39v)
u must add hysteres-band for eatch comparator...use some logic circuit to get
led sequence operation
if ur circuit work with a batt u should be take areference voltage for comparator
from reference like TL431 .
 

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