Picture of Outdoor LED Thermometer
If you don't want to read any pointless chatter you can feel free to skip to page two.
You have been warned.
Over the summer I once again was looking for a fun project, that I could learn something from (AKA mess up twenty times, and correct my mistakes then try again). As I walked outside it was burning hot, my best guess was 451 degrees Fahrenheit (yes that was a reference) or for everyone outside the United States 232.778 degrees Centigrade (The joke doesn't quite transfer as well). Anyway, on that day I knew I wanted had to know the temperature all the time when I was outside. So, I went online and looked for outdoor thermometers. As with my desk none of them were what I wanted and I thought I could make one myself. So, I started on the project off and on. In all it took me about 3 months (Most of which it just sat there) to build my thermometer. In the end I am pretty happy with the results. There are a few thing I would like to change if I was going to do it again, all of which will be listed in the different steps as there are relevant. But, in the end I had what I set out to make, and it even looked good. :)

Disclaimer: I have no formal education in either woodworking, electronics, or programming I am completely self taught in all three areas. Thus, I cannot promise that my work will follow any conventions of the three. And for anyone reading my programming, I know it is very inefficient  and if someone would like to rewrite it for other I would be happy to upload it will give credit to you.

Safety Disclaimer: The use of tools can be dangerous, please use common sense. I cannot be held responsible for any injury due to misuse of tools. That includes injury to animals that may be in the vicinity of your work space.

Answers for the Make to Learn Youth Contest

What did you make?
I made a digital outdoor LED thermometer. The thermometer comprises an AtMega328P which analyzes the one wire digital temperature sensor, which is then displayed using a custom 2.1 seven segment display (two full digits and a one) made by 10mm LEDs. Each controlled by a MOSFET mounted on a custom PCB. In addition to the electronics, I also produced a suitable wood enclosure made from multiple boards of poplar and plywood. Finally, I used the Arduino IDE to write code for the AtMega328, I then uploaded the .Hex file created by Arduino to the chip with an ISP. If you would like to read more of the reason for the project the first paragraph provides a dramatized account of my choice to make the thermometer. 

How did you make it?

After searching the web trying to find a outdoor thermometer I liked I came up empty. So I decided to build one on my own. (In hind sight it would have helped to get someone who knew what they were doing to help). As I started out I had a set plan to take a precut circular table lazy susan top and route out the back. Well that didn't work which describes much of the project. I would plan for a certain path but many times I had to rewire/recut/reflash to finally get a working thermometer. More of detail is available on the third and fifth step.

Where did you make it?
I did all the major work on the project at my house. All the woodworking was with my limited tools in the garage, the soldering was on the kitchen table until my mom kicked me off. While all the actual work went on at home, much of the deign went on during school when I had free time in classes or was just bored I would sketch the redesigned circuit or think about a better way of constructing the enclosure.

What did you learn?
The biggest challenge for me was designing and building a circuit that could drive multiple segments of LEDs which required a higher current and power than the AtMega could provide per channel. The biggest surprise to me was how well it actually came together in the end. I had some what expected to finish it half way and then give up after getting one part to work, but I finally got all the parts working together. After was all said and done the proudest part of the build was the PCB I designed, after soldering up the whole circuit on proto-board I decided to design and have manufactured a PCB which I think turned out beautifully. If I had to do it again I would probably spend a little more time on the enclosure because I have some ideas on how to improve its function and performance.     
More information is spread through out the instructable which answers the questions. These answers are just a summary of the information. 
nodoubtman2 years ago
how do i transfer code from arduino to atmega328p chip?

thank you!
Sobaka-Gemini (author)  nodoubtman2 years ago
Once the code is in the Arduino IDE hold "shift" and click verify. This will compile the code and create a .hex file. The file location should be displayed at the bottom of the arduino IDE. If it is not there it should be somewhere near C:\Users\"Your User Name"\AppData\Local\Temp. The file will be in a folder named "build" followed by multiple numbers. Open the folder and inside look for a file named the same as the sketch. This file will likely have a ".cpp" suffix but will say HEX under file type. Once you have this file you can upload it using a In System Programmer "ISP". For this purpose an arduino should work (I have never tried) a explination is avalible at http://arduino.cc/en/Tutorial/ArduinoISP . Or a true ISP such as USBtinyISP (Which is a kit). Or many other options, a quick search of AVR ISP will revel many options. I then use AVRStudio to set the fuses and apply the code.
jkeeeng2 years ago
Where you have got your PCB from? How much it cost and how long it took from the sending ur PCB design and the day u have got it done? Thanks!
Sobaka-Gemini (author)  jkeeeng2 years ago
I got the PCBs from http://oshpark.com/. They require a minimum order of 3 copies. Which in total cost me $25. It took around 2 or 3 weeks, if I remember correctly. Overall, I was very pleased with the final boards quality.
Nice project - arguably you could do with some arrays and loops in your code, but the key thing is that it works!

I have also used OSHpark and found them very good, especially for very small boards. Postage is free in the US I think (I'm not in the US) and they charge $5 per square inch for three copies. There's quite a lot that you can do in a square inch or two!

If you go slightly larger then iteadstudio.com currently does 10 boards at 5x5cm for $10. My first boards from them are in the post but I'm told that they are good.

One other thought, if you ever want to drive multiple digits again, is to look into the use of shift registers (the "shiftout" tutorial on the Arduino web site will give you the idea). They allow you to control many digits together, all from three pins and leave many more pins available for other tasks.

Looking forward to seeing more projects!

jkeeeng2 years ago
Where you have got your PCB from? How much it cost and how long it took from the sending ur PCB design and the day u have got it done? Thanks!
danbemp2 years ago
Very cool idea! I like that you've shared your experience with us as you went about designing it and making it.

Put up a video of it in action!
Sobaka-Gemini (author)  danbemp2 years ago
Thank you, I will try to upload a video soon.