Hi im new on the forum, i saw how good it was and joined hoping you guys could help me.

Im doing a BTEC national diploma in electronics and electrical and i have been asked to do a year long project for the course.
This project invovles me designing and making a electronics circuit, but having me making the circuit so it works at the end of the year is only 20% of the final mark, the rest of the project is ALL paper work .

So i have been looking and encouraged by my tutors to look on the internet to find a project and its circuit diagram already done for you, so all you have to do is use the circuit diagram and make the circuit your self quickly, so you will have enough time to complete all the paper work.

I have decided to make a Temperature sensor circuit which is connected to a 7 seg display or LCD display; all i need it to do i record the temperature and then display it, no more no less.

So im just asking if anyone knows of any good sites or ciruit designs out there, in books or on online to help me out, any advice would be greatly appreiated as well.

At the moment the idea i have in my head is just a simple thyristor temperature sensor which goes through a A to D convertor which is then connect to a PIC or other chip which will then display the temperture on the 7 seg/LCD display.

Thanks for any help in advance and sorry for the long thread
Resonance

 

What is BTEC ?

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Its a English (yes im from the UK) qualification.

http://en.wikipedia.org/wiki/BTEC_ND

 

Bachelor of Technology , Guess so!

 

I'm sure you meant thermistor instead of thyristor. They are different animals.

A thermistor does not have a linear response to temperature, and would require a lookup table or data manipulation to give accurate results. Use an LM34 or LM35 as the sensor. The output is linear, and already in engineering unite - one in C and the other in F. Makes life easier.

 

I agree with j.p.bill, the LM35 is definately the way to go. I seem to remember that you need to be careful about your cable lengths with it though? Have a good read through the datasheet!

Brian

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Electronics Test Development Engineer
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The LM34 / LM35 are easy to use little ICs.
Not much to write about in a report though as all the hard work has been done for you.

Writing about a thermocouple or thermistor would be more challenging.

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I think you should look into the DS 18S20 temprature sensor, that way you could avoid all of the ADC issues.

 

Hi Guys,

Thanks for the really fast responses, i have been searching through your forums for the whole afternoon and i have found another thread with the perfect answer on for me.

http://www.electro-tech-online.com/g...ut-w-o-uc.html

Heres the link to the circuit i will be using.

http://www.100acre.org/elec/lm75/

Thanks again, this site has been so useful, i will be sticking around on here for a long time getting help and also giving it out when and where i can!

Resonance

 

Hmmm - it uses I2C. Not a problem, but you'll need to be able to explain all of this in your project report. I recommend you do some research into PIC programming so that if you're asked questions of it, you can come up with answers. Also you'll need to know how I2C works, and where it's being done within that program.
There will also be a number of other functions and sub routines you'll want to find out about. For example, how is the display refresh being done - multiplexed I suspect. There are a couple of ways of doing this, you'll need to know how it's being implemented within that program. Are there any calculations done on the raw data that comes back from the sensor? etc etc

Brian

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Electronics Test Development Engineer
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Oh by the way, you really should know a little bit about JAL as well!!!

I hadn't actually heard of it before myself, apparently it's a high level language for PIC Micros.

Brian

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Electronics Test Development Engineer
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There's no reason (or need) to know about it, unless you want to use it?. JAL stands for 'Just Another Language', and is just another HL compiler - looks a bit like C, a bit like BASIC, and a bit like Pascal

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The reason I mention him needing to know about it, is because the program he's going to be using for the PIC was written in JAL. So unless he's planning to re-write it himself in a different language, he'll need to know how JAL works. For no other reason than if he's questioned about it, he'll need to sound convincing that it's his own work!!!

Brian

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Electronics Test Development Engineer
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Guys thanks again for the responses,

Do not worry about the PIC programming side of things, i am learning it on my course at the moment, so i will re-write the program using are own software we have at college.(will tell you the program were using on monday, i cant remember the name of it )
Last year we learnt pascal and C++ programming languages so PIC programming will not be strange or hard for me, i just have to learn it .

I have my tutors to help me if i get stuck at the programming and i will be showing them the circuit diagram and this forums, so they can tell me if im heading down the right path, i will inform you of any changes or help i need.

Thanks you guys so much for all the help this forum is brilliant.
Resonance

 

I think one of the project aims ( if you are going to build an exist one ) is to go steps further.
my suggestion, since you are going to use PIC, is to include some extra facilities, such as setting an alarm threshold, giving audible or LED alarm indication and any sort of control, Relay output perhaps.

This may challange your skills and boost your self confidnce than feeling Copy & Past.

All these facilities are easy to do with PIC since all are DIGITAL OUTPUTS.

Gooooooooooooooooood LUCK

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