2013. február 2., szombat

Beginning a new project

Below is my 10 points I follow when a new project hits my mind. This may differ from people to people but it works for me at last. I always start like this:

  1. Search for many information, like textbooks, articles, examples, datasheets
  2. Write down your requirements
  3. Organize the information, make folders, download datasheets
  4. Select the main parts You can or want to use, this depends on your knowledge or source of parts
  5. Check if the known parts are capable of doing what it should or search for the appropriate part, manufacturers page can help in that a lot
  6. Begin to draw the schematics, I use Eagle in my projects
  7. Decide on the building method, like surface mount or trough hole, desired PCB size or just protoboard
  8. Start your layout with the part in the most important positions, the others must fit around that
  9. If you are happy with your layout, double check for possible improvements
  10. Before going shopping and sending the files to a professional PCB shop triple check everything, take some time between two checks, like a day, to see if you are still sure everything is as intended to be

I think myself an amateur in electronics design but hopefully an intermediate amateur. For trying out new things and learn how their work a beginner needs some tools. I will talk about microcontroller based projects, in the future, so when your plan is to learn tube technology you will not find many useful information below.

Once I learned C and had my very first microcontroller programmed, I saw how many possibilities lying before me. At this point I made a statement.
First, I am not a professional, I won't use 132 legs MCU with 32bit architecture. I am not a linux programmer either.

So I went to the part store, and checked the Atmel Attiny and Atmega family microcontroller prices. For my initial ideas I decided I will not be using MCUs above 1000 Forints, about $5.
Building more complex programs, the first you will notice 2kbyte RAM is plenty! I have to tell you I did never fill a 2k microcontroller program memory to even 90% with my most complex design.
Storing lookup tables is another story. For that I may use I2C memory that is cheaper but that depends on the table.
Well, for that price limit I have many choices, I still do not ever buy a microcontroller that cost me more!

The next step is to use SMT parts.
Why use SMT parts?
Surface mounted parts has some benefit when you are designing a nice little circuit. For me after thinking of the drawbacks are still the preferred technology. I made a list why:

"Surface mount"
"Though hole"
Cheaper parts Costs more

Less PCB area needed

Uses more pcb space

Often need 2 sided PCB Fine with 1 sided pcb
PCB needs conductive vias Fine without vias
Difficult handling and soldering Easier to solder
Quicker to solder More assembly time
Some parts only available in SMT DIP ICs not always available

My first complex circuit was a breadboard monster. Some parts were SMT cased and for that I bought a few DIP adapters from eBay that worked perfectly. When I realized the benefits of surface mount technology It turned out a professionally manufactured PCB is always better. First I used the bigger parts like 1206 size, now I use 0805 where I can. A PCB populated with SMT parts are always smaller and smaller PCB area is cheaper.
It could turn to a habit to make the circuits as small as possible. In my designs I use the less possible space to stuff things on. There are always some THT parts, at least the connectors and somethimes capacitors. I use THT relays for example.

Now we are good for the first few items in the checklist, the next one needs a CAD program to draw schematics and do board layout. There are some free alternatives too but I recommend Eagle from Cadsoft. The free version can do 2 layer boards in 100 x 80 mm dimensions which is plenty if you use SMT parts.

If You are new to SMT technology, I recommend you to watch a video how to solder really small parts, on YouTube there are very good videos on that. Search for "SMT soldering". Its fun.