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Idea
This project was born with the need to stand out when trying to get contracts,
Jumper Business Card had to fulfill a mouthful of categories. It had to be fun, entertaining, minimal, smart and cheap enough to give away, but at the same time impressive and immersive. I wanted to create something that people would come back to. I didn’t want it to be a one time look and throw away type of deal. I wanted for people to come back to it and pick it up again, be it once, but pick it up again. It had to be a game and an addictive game at that.
My mind started rushing with ideas. All the sensors and their applications were hitting my head. All of it seemed cool and fun, but unpractical, complex to develop and with potentially a lot of holes that would take ‘way long’ to make or on the other spectrum of the extreme, it was simply too dull. I looked at my inventory of components, and one particular thing stood out to me like a sore thumb. I had reels of thousands of LEDs from my trip to Shenzen, China. The wife was not thrilled about all the components I bought while in the Shenzen Electronics markets.
OK. LEDs… We can Multiplex them or Charliplex them to make a cool LED display. That’s a lot of components to put down, especially since the assembly is going to be inhouse. That’s when it hit me. Limit the number of LEDs to create a ‘simple’ display in a horizontal direction, throw in some “objects” that will scroll and have a “jumper” that needs to jump over the obstacles. Yes… Just like the “Dino” game on Google’s Chrome browser, but a handheld version on a PCB. How cools is that? Well, it actually is pretty darn cool. It fulfills all the necessary categories, it’s entertaining, simple enough not to burry me for weeks and it will require some fun code.
Organization
Alright, so what do we need to actually make this thing? Well for starters we need to organize the idea.
- Description of the Project
- Research
- Design
- Manufacture Prototype
- Code
- Fix
- Manufacture of Final Product
These are more or less what goes into designing a product. Each step has many small sub-steps that we need to take into account. More on that later as we explore how this project came about. Another critical thing to note is that some steps are prerequisites while some require concurrency. It is a complex/living/fun process.
Documentation is the key to success. Throughout the project, notes are carefully kept, and even the bad ideas are written down as you never know what turns out to be the right approach in the very end.
Step 1 – Description of the Project
Step 1 is the most crucial step. Without a good project description, it is hard to move forward as it is a stepping stone for everything else. It is important to describe as many aspects of the projects as possible. These descriptions often cannot go into much detail about implementation, and that is not what we are trying to achieve here. We need to describe what the project is and what it needs so we can decide on the specifics.
* NOTE: It should be pointed out that Step 1 is AFTER the idea is conceived.
The project description can take many shapes and forms. My favorite is to write down all requirements in a bullet point form along with
- Handheld
- Battery Powered, non-rechargeable
- PCB without enclosure, cost and wow/raw effect
- Size of a business card (approximate)
- Single-button operation
- On/off switch for simplicity
- Easy to hold and operate with a single hand
- Informative (silk)
- Linking to this site (QR not possible on silk due to resolution – sticker)
- Decorative – logo/slogan
- LEDs as a “screen” in a 6:3 horizontal configuration
- KE04 as the main chip for cost, size
and number of I/O.
A written description is also a good idea to communicate artistic design, etc. In our case, it will be up to me to design it so that I will leave it out of the description of the project.
Step 2 – Research
Now that we have a good description of the project, it is the time to make sure everything looks good and is possible to make. Research plays a vital role in this portion of the process as it will determine if the project is feasible or if it needs alteration to the description. At this time we will choose all the components, read through their datasheets, and make sure that all of them are in-spec.
Research is a crucial part of the project and should not be taken lightly. A mistake here can cost a lot of money and delay the project. While it is human nature to make mistakes, it is essential to go over this step more than once, to eliminate as many as possible. That being said, it is crucial to make sure all specifications for the MCU and other major components are within our specification. Components such as the MCU are hard or even impossible to replace if something does not work.
For this project, I needed to make sure that the main chip has enough IO as we did not want to Multiplex or Chariplex. I wanted a chip I have worked with before as this would speed up the firmware development. The chip also needed timers, while a single timer would do the job, having three made the job easier. The chip also required to have external interrupts for the button. It also needed to be as cheap as possible. The best choice was the KE04 by NXP.
This is where I rushed a bit too much, and it bit me back. My idea was to run the entire device on a single cell 3V button battery. I glanced at the datasheet of the battery, and everything looked good, except for the fact that I made an assumption. The battery needed to be able to discharge at a rate of 100mA from time to time, and the expected constant discharge rate was to be at around 20mA. The button cell battery I chose was rated at 2mA not, 20mA constant current. This threw a small wrench into the equation. More on this later. Regardless, this taught me a lesson.
Part 2: Hardware Design