# [help] home weather monitoring miniproject

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by alkoko111, Jun 29, 2009.

1. ### alkoko111New Member

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hello .. eric ! i want to ask about something

About the temperature . someone implement the project like me with these values :

Vref=1.28 v . applied on pin9 is 0.64 v
LM358 works as buffer .

he used these formulas :
To get the minimum span that the adc can identify . min-span=Vref/255
To get the Vin . Vin= Dout * min-span

then :
=1.28/255 = 5.01 mV

He that this the min-span according the formula. and we know that the adc will give us 10 mV / centi but here will give us 5mv/centi ..... which mean we will take the output of the adc and divide it by 2 to get the tempr .

example : if the output is 00000010= 2 in decimal then the program will read 2 and divide it by 2 to get the tempr ...... 2/2=1 c .

is that make any sense ? i asked him about why you divided by 2 ? but he did not respond till now ?

what do u think ?

note : the program is working fine as this person illustrated .

2. ### ericgibbsWell-Known MemberMost Helpful Member

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Hi,
I would still advise to use the LM358 as an amplifier for the LM35 output also use the ADC's internal 5Vref.

3. ### alkoko111New Member

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okay .... i think this is convinced . thank you so much ...any new doubt i 'll DISCUSS it with you .

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5. ### gnldsNew Member

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Hi, I have a thermometer project and I need help. I created a few circuits with different way. Although it seems correct, they didn't work. I added different versions of my project, please help me to solve this problem.

Thank you !

You can download .DSN files:
http://rapidshare.com/files/392829295/Projects.rar.html
Hotfile.com: One click file hosting: Projects.rar

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Last edited: May 29, 2010
6. ### edecaActive Member

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It is best to start a new topic if you have a new question.