Temperature Probe

[airbornflght]

Okay me and my friends are building a certain aparatus that will reamain un-named. What we need is 3 temperature probes, as temperature control is very crucial. I was thinking of useing 3 of THESE diplays, maybe with the label for the probe on the top line and the temerature and unit in the bottom line.

When It comes to electronics itself, i know a little bit more than jack schitt.

for two of the probes, I need them to be able to withstand temperatures upto 200 degrees Farenhieght, and must also be able to withstand steam. the third probe will be wrapped around one of the condenser pipes of an oil cooler, or possible mounted inside. I need this one to be water proof as well, but does not have to handle the adverse temperatures.

These probes will be comming into contact with a food material (with the possible exception of the third) so they must be either stainless steel or copper and have no lead or aluminum in them. Am I correct in that I will need a thermistor wired up to some sort of controler? i am clueless, but I am pretty sure that this is a simple thing to do. My friends dad is an electronics guru, but I have not had a chance to talk to him, but would like a possible schematic/pcb layout before I talk to him and i'd like to know what im talking about and what needs to be included.

I am trying to keep this on the cheap side, hense the reason I chose a $3 2 line backlit lcd. The temp probes need to diplay the temperature with .1 * F of precision. im sure you all know what im talking about, or at least get an idea from my vague description.

[windoze killa]

Well to start with 200F is not all that hot. Not even boiling yet. Most semiconductor manufacturers make temperature sensor chips. For example an LM45 is a 3 pin device that we use here quite a bit. It is rated for -20C to 100C (212F). This is quite small but it is an SOT-23 style package which will probably not pass your food requirements. There are other devices that are similar that come in a TO 92 package that may suit your needs better. The LM45 has a linear 10mV per degree C output. Just need to feed this into a micro controller and write some code to suit (sorry , not my forte).

Sorry I don't have time to do a schematic for you but I am sure if you have a look at some datasheets you should be able to work it out.

[airbornflght]

thanks for the heads up. I am really pretty clueless when it comes to the different sensors and such. the main things that I am wondering is what language this stuff runs on (is it the same language for all the stuff) i am assuming it is probably basic or assembly.

[gogo2520]

Hello airbornflght

    The microcontroller windoze killa is talking about could be program c, c++, basic, or asm. It all depends on what compiler you are using. You said you got a LCD for 3 bucks, wow did it come with the controller?
                                                  gogo

[MP]

airborne,
Here is a link that will help you on connecting a temp sensor to a micro using a free basic complier and in-circuit programming so that you will not need a programmer board. Of course, you can also use a chip with an on-board Analog to Digital converter and not need the adc chip.

http://www.mcselec.com/index.php?option=com_content&task=view&id=68&Itemid=57

MP

[airbornflght]

yeh, the link is on my first post for the lcd screen, could someone point me to a website, or post a short walkthrough on the different componets and there function in a circuit like this, the most complicated circuit ive made is a serial paralell led circuit.

right now I am pretty clueless. all i know is Temperature probe --> lcd screen

Work dam*-it!! ::)

now anyway, back to reality

Ive been recently thinking about buying a graphical display, but im sure runnign one of these and getting it set up is pretty complicated. and would it be possible to hook say 2 probes up to one screen, so that the top line would display

prb1: xx.x*
prb2: xx.x*

[MP]

You wouldn't actually be hooking these up to the screen. You would connect to the micro and display to the screen. You can display anything you want on the two lines of the display. You could read 4 sensors with the micro and display each temperature on separate lines of a 4 x 20 or 4 x 16 line character display.
Graphical displays will take more code and are not necessary if you only want to display words and numbers.
Here are some other websites that can give you ideas from displays and temp sensors:

http://www.avrprojects.net/

http://www.compsys1.com/workbench/On_top_of_the_Bench/BascomAVR/bench_avr.html

Hope it is helpful

MP

[airbornflght]

thanks for the reply, i looked at those websites, mainly the first one, although, im still a little confused to what needs to be done, but im gonna tell you what i know then you can correct me if im wrong. the lcd I am wanting to get has a controller built into it so yeh


as far as i know, heres how i think it goes.

temperature probe(s) go into a micro controller that is programmed to figure temperature in farenheight via a formula dividing input voltages by the constant.

the micro controller sends the signal to the lcd controller which interprets the signal and sends the correct information the display and the display shows the data that I need i want it too.