First serious project-Device to check melting points

Using Arduino General Electronics
1

I know what needs to happen, I'm just not sure how to make it happen. I'm going back to school for chemistry because I love it and even at my age I think you should pursue the things you love. Anyway, I'm building a device to check melting points. I have a surplus heater from a coffee pot I got from American Science Surplus that runs straight 120v and draws 8a, supposedly this little thing will get very very hot. It's shaped like a cup, or a shot glass, more accurately. I have a small lathe and will be making a stainless steel plug that goes in the 'cup'. On top of that stainless steel insert I will have a very small ~6mm radius in the center highly polished that will hold the specimen being checked. For components, I have a thermistor on it's way from sparkfun (10k), my arduino uno and most of my basic odds and ends. Switching of the element will be done with a solid state relay. I also have a nokia 5110 lcd I would like to use for visual feedback of temperature and other settings, if there be any. In a perfect world I'd want to interface the arduino with my computer and write a small piece of software that starts the element heating and upon my pressing of say, the space bar, it stops heating and records that temperature. In a realistic world, however, a start/stop button attached to the arduino is fine. Perhaps even incorporate a potentiometer to either limit top end temperature, adjust the speed at which the temperate rises, or both. Again, that is secondary.

My question (the first of many) is what do I need to learn in order to make the arduino begin pwm-ing the relay when i hit go, stop when I hit go again and have the current temperature displayed in real time on the lcd? All the other functionality can be added later. I'm really motivated to build this and that's the best way for me to learn. I'm beggin' here, help me!

I'm not afraid to read, I just don't know what to read lol. Also, any advice from experience with thermistors and reading accurate temperatures from them would be awesome.

Thanks a million, guys!

2

So you're saying that the first things you want are button functionality, and temp display?
as for setup of the LCD, you should probably have a driver for the LCD like a shift register or something.

In pseudo code, I'd say this is generally what you need:

initialize variables and such;
void loop() {
read state of buttons and debounce;
if (button pressed) {toggle PWM}
read thermistor, use whatever math to determine temp;
send temp value to LCD driver;
}

I hope I'm not just telling you what you already know.

3

There are examples of both driving an LCD display and using a thermistor (and the math involved) in my book '30 Arduino Projects for the Evil Genius.

You can see information about the projects and download the Arduino sketches from here:

http://www.arduinoevilgenius.com.

So if you can do the hardware you probably don't even need to buy the book.

In fact, there is an example of both together in the form of an LCD thermostat - Project 22.

4

Thanks guys! Time to get this ball rolling. I will keep this thread updated! At work now, so I can't say much besides thanks!