electronic thermomter

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cs200939

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Hi i need help with my circuit theory project.we are just asked to come up with some interesting project after a month.Right now i am totally empty of any ideas.now some of my seniors have suggested building an electronic thermometer.theres nothing i know about this project.I mean when at first i heard it i just thought of a thermister,transistor ,a battery and some hot and cold enviroment and voila!!.. but as it turns out its actally very complicated!..so please help me out with this project.i am strickly told not to use ICs i mean i can use one or two but not more.And since i dont have any knowledge about this project please post the easiest and simplest to make schematics.And yes acuuracy is not my concern.it could even be 1 to 2 degrees less or more..i jsut need to show that my circuit can sese temperature changes and display some valid values of that temperature.I'll really apreciate your help.Thanks
 
Thermistor, transistor, LED?
Thermistor, op-amp, bicolour LED?
LM35 and an LED bar driver IC?
DS18B20, PIC, 7 segment display?

All solutions, varying difficulty (ranked easy to hard).
 
Hi cs200939,

here's an easy one.

Besides the temperature sensor (LM35) it contains just the allowed max number of ICs. It measures temperatures from 67 to 86deg/F (19.4 to 30deg/C) in one degree steps.

Half degrees can be read by interpolating the brightness of LEDs.

Accuracy will depend on the accuracy of components used, but can be down to 1/10deg/F.

In this configuration the readout is limited to dot indication. Bargraph indication is not possible.

Interested in the Eagle files? PM me your email address.

Regards

Boncuk
 

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hey thanks to all of you for your splendid information but the problem is that i am very very new to ealectronics and dont know much of the stuff you are talking about like the LM35 IC..i know its a temperature sensor but how to extended it to a full fledge electronic thermometer is big question mark for me.will it be good if i start witht the schematics containing the op amp,thermister and bi colour LED and then moving upto LM35?please suggest..thank you
 
Look up the LM35 temp sensor, you should find some circuits you can use. Andy
 
i tried to but cant find any that i can actaully understand or easily implement.its just a college project and i dont have any good knowledge about the project.no doubt these forums have helped me alot in most of my projects so i am quite dependent upon you guys so please help help.just 2 weeks left for submission
 
If you are dependent on us it means you have not learned anything. What is your electronic knowledge? Reading the LM35 datasheet shows it outputs 10mV/C. Also, is this IC readily available where you are, if not you will need to consider other options.
 
what i mean is that so far the knowledege i ve gained in electronics other then what i ve been taught at college is because of these forums.my knowledge is dependent upon these forums not me..yes this ic is available.but how to use it as a temperature sensor and get a reading in Farhenhiet is what i dont know.i mean the whole circuit offcourse.
 
I would suggest the LM3914, it's linear. Doing a bit of math with the 10 Led's you can either approximate the temperature (3 degrees per LED) or have it go for instance from 20-30. Wait Fahrenheit...hmmm you do the math!
 
I think the biggest beginner mistake is rushing through a project without understand. I would suggest reading both data sheets and gathering what information you can from them.
 
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