Soil Moisture Business Card | Part 2: Concept Generation and System Design (WIP)
In my previous post, I arrived at the 3 main requirements for my PCB business card design:
Functionality that can be demonstrated at the moment of handover.
Usability and understandability by someone with no technical knowledge.
Minimum total thickness.
Taken from: https://medium.com/great-ideas-from-someone-still-figuring-it-out/i-dont-want-your-business-card-afe47402b3ba
It is interesting to note that none of these are specific technical, or application contraints. But rather within them they encode many. For instance, any computer peripherals are out. Likewise, anything that needs a screen, or perhaps is a development platform and so requires coding knowledge.
There are also other themes that are desirable. I do not wish to give someone something that, while fun in the moment, quickly ends up in the trash thereafter. This, in my view, is almost worse than a normal business card, which at least is small enough to retain ownership of until a time which my skills and contact information may be needed. I desire a concept with a bit more ‘staying power’.
This does create an immediate technical challenge. How do you power such a device?
If it uses a coin cell, then that is a thick, heavy component that still retains a limited lifetime. Coin cells do not typically provide enough power to run LEDs for a long period of time, rather they work well for data storage, or irregular BLE broadcast.
If it uses a rechargable battery, than that is likely even larger. It is capable of delivering more power and opening up effectively limitless applications, but at the cost of requiring a provision for recharging - almost necessarily a micro USB or USB-C connector (although wireless charging could be an option using a PCB antenna). There are also complications and risks including LiPo batteries in any product.
Neither is a good option and that is why you see PCB business cards powered externally.
