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Automotive thermometer with LCD output

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911alertme

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I just purchased a vehicle and it doesn't have a thermometer in it. I thought it would be nice to have a thermometer in it. What I want is something decently small. It seems that everything available commercially is a bigish box that would be really hard to mount discretely.

I am thinking of using National's LM35 analog temperature sensor. I want it to output the temperature to an 8 segment display (three sections? long). I know that this IC has an accuracy of 0.5C but I want to have a resolution to one decimal place. I understand the difference between accuracy and resolution and I know that the decimal may not be really accurate.

Now the part I need help with, what is the best way to get the reading onto the display. I know I could use something like an Arduino or STAMP or something but those aren't that cheap and I would like to use something a little more minimal in this application. I have some experience with a STAMP so I have the basics of a micro-controller down. Also, programming shouldn't be an issue. I have no experience with displays. What do you recommend for a display and micro-controller and how do I hook it up?
 

Noggin

Member

911alertme

New Member
I looked at it and it says it operates down to 0C. In the winter here it goes down to -40C. Thats not going to work.
 

jkmadsci

New Member
This kit looks interesting. I currently work only with pics. how hard is it to fire one of these up and write a small program ?
 

Noggin

Member
Assembly or C? If you do assembly, the AVR assembly is LEAP YEARS ahead of low end PICs... no bank switching and 32 working registers. More MIPS too. If you write C, not much different from PIC, just have to get used to the documentation. I think AVRs are better documented, but that may be because thats was my first micro. You shouldn't need a programmer either, the butterfly comes preloaded with a bootloader. If you DO need to get a programmer, you can buy an AVRISP MK II for $30 and they'll program any of the AVRs.

911alertme.... I think you're going to have problems with any LCD at those temperatures.
 
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911alertme

New Member
What about a seven segment, 3 digit, LED display. Those are rated much closer to -40. The only thing is that that uses a lot of pins. It needs nine pins a digit I think * 3 = 27 pins. Thats alot.
 

Noggin

Member
The pins used to control the segments can be shared amongst each character. Each character would have an enable line so you'd disable all characters, set the segment control lines, enable character 1, wait, disable character 1, set the segment control lines, enable character 2, wait, etc....
 
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