The first obvious choice was to use Raspberry Pi Zero. Even though I have known that would be too expensive and unavailable for mass production. For the first 3D prototype it was just fine. Specially thanks to the fact I can SSH into it and change the code remotely.
I was trying a few different shapes but had a more-less pretty good idea of how it should look from the beginning.
Display issues
“Another first obvious choice was to use 7-segment displays. That quickly turned out to be a dead-end, as it's not possible to make a crypto logo with it.”
So I started to think about two options - LED matrix and OLED display.
From the beginning, I wasn't decided if the display should be white only or coloured. I liked the idea of it being just white as it had that nice and clean feel, but on another side, I have understood, many people may like that orange BTC or blue ETH logo...
OLED displays are pretty expensive... I learned that the hard way. I had no idea it would be such a big problem. You can get the OLED display with the right size... it would just cost more than the whole product retail price... And that stopped me for a while.
The forbidden prototype
Once I have discovered the prices for OLED displays, I turned myself into belief, I need to make the display from the SMD LEDs. Later I have discovered, it's not much cheaper after all, and also... It looked horrible... You can tell yourself... Not only it looks terrible but also cost me around £200 to make it. Well... I'm not sorry after all, as I needed to do that to find out this is not the way to go. That's the price of the prototyping. The final prototype itself can be quite cheap, but until you'll get there, you can spend at least 10x more in the process.
Light at the end of the tunnel?
“Now I know I needed to use the OLED displays. Problem was, they were too expensive.”
After I have tried a few different approaches but realised I may try to "cheat" a little. I have discovered the common 0.96inch OLED for Arduino are quite cheap. They are too small by themself of course, but then I tried to join five of them in a row and discovered, it doesn't look so bad once covered with black translucent glass. It's supposed to show the numbers and the numbers have a gap within them anyway, so it looks like I hit the sweet spot. The reasonable price and if I didn't tell you it's not one, but five displays, you couldn't tell at first glance.
A couple of other things
I have thought about the right size and shape for quite a long time. As you can see on the fifth image in the gallery I have tried to make even the bigger version with a bit of different shape, but after all, I stayed within the original design.
You can also see on the fourth image, I wanted support for different crypto as well. I truly believe in Bitcoin only, but I also understand someone may like to see the prices for altcoins as well. Many people are concerned if it can display enough digits.
As you can see in the last photo of the gallery, it can easily show 7 digits, but if the currency and crypto logo is moved or removed, can show even 10digits. After all... once BTC price will reach to 10digits, I believe we will have whole new different problems... with our new yachts 😄
Written by Pavol Bujna
17th Jun 2021