Entries in circuit board (2)


PCB Business Card

I’ve been seeing a lot of printed circuit board (PCB) business cards on the internet these days, particularly on hackaday, so I decided to jump on the nerd bandwagon and make my own. I searched google images for inspiration and found this one, which I thought looked pretty awesome. So I copied the general layout, but with a few minor changes. First, I designed my own circuit using a Propeller chip, 8 0603 (very small) LED’s, and a surface mount (SMT) battery holder. Second, instead of having white text on a black solder mask, I put the QR code and text on the solder mask layer. That way, the silver board will subtly show through from underneath.

I put the order in to Gold Phoenix last week. I choose their normal 155 in2 deal. It’s a really good price - without any option it’s $110. In my case, I ordered their thinnest PCB material, and added black solder mask. The total came out to $130 with shipping to the US. Expensive business cards at $6 each, but I don’t anticipate handing out too many and it would have cost way more if I had ordered them from an American company.

Here’s the board as sent to Gold Phoenix.Gerbv render of the Gerber files sent to Gold Phoenix

As for the circuit, it really is overkill. I’m not actually going to be able to afford to populate the boards, but as long as I didn’t make any errors, it should work. The the propeller chip is $8, and all the other parts added to the price of the bare board will bring this card to almost $18.PCB business card schematic

Download the Eagle Cad files.


Matrix Badge

So, last year I spent close to 100 hours laying out my smallest circuit board, even to this date. The only problem is that I couldn't get it to work. I think I figured it out. I made the mistake of designing the board around a quad flat no-leads, or QFN, Propeller Chip microcontroller. In hindsight, I should have used a quad flat package, or QFP. QFN's are notoriously difficult to solder, and still often develope solder bridges. A solder bridge is a when two or more adjacent pins develop a 'slick' of solder that bridges the pins, making them electrically connected.

Cut to a few days ago. I got 4 boards in the mail from Advanced Circuits. A couple weeks before that I put in a new order for my matrix boards, with a few minor tweeks to the original design. This time I elongated the pads for the QFN prop chip. Hopefully this will wick the extra solder away from the Prop's pads and help prevent bridges. We'll see.

Old QFN (small pads)New QFN version (notice the elongated pads)

I realized I have explained what the boards do; here's a summary:

  • Parallax Propeller chip
  • 64 0603 surface mount LED's arranged in an 8x8 row/column matrix
  • Two choices of lithium polomer battery
  • On-board battery charging when plugged into USB, via MAX1555 chip
  • USB programming via FTDI FT232RL chip

The point of the board is to allow the user to program it to display messages on the 64 LED's. Another possibility reccomended to me on the Propeller forum is to Program it to play Conway's Game of Life.

I've been extra busy in school these days, so I'm not sure when I'll get a change to solder up one of the new boards. But I'll be sure to post my results here. For now, I'll leave you with a photo of the tightest (in both senses) board I've designed. Sorry for the blurry iPhone photo