EKG blinky

I ordered a printed circuit board from OSH Park, which has replaced DorkbotPDX that I blogged about a week ago.  The price is still just $5/square inch for 3 copies ($10/square inch for 4-layer boards), including shipping.  I submitted an Eagle .brd file tonight that I designed today.

OSH Park’s artistic rendering of the EKG blinky board. The battery clip (for 2 CR-2032 batteries) takes up most of the space and the batteries will be most of the weight. There will be 3 screw terminals on the upper left for attaching the EKG leads, and the blinking LED in the bottom right. I added a trimpot to the design so that gain could be adjusted as needed.

OSH Park’s artistic rendition of what the back of the board should look like. Soldering may be a bit tight, but not as bad as SMD parts.

The board is a version of my EKG circuit including an LED that should flash in time with the heartbeat (as well as providing header pins for attaching to an Arduino or oscilloscope.  I feel pretty pleased that I got the board down to about 2.4 square inches, so I’m getting 3 copies of the board for $12.15, especially as I used all through-hole parts and most of the space is taken up by the battery pack.

I’m not planning to have students solder up this board for the circuits class—there is no design task there, just technician-level skills.  I plan to design a somewhat larger board that allows prototyping instrumentation amp circuits similar to this EKG circuit, but which doesn’t have fixed wiring.  I’m still trying to decide whether to have resistors lying flat (as on this board), or mounted vertically from the board, as I usually do on a breadboard.  For this board, since the result is a wearable EKG, I wanted as much durability as I could easily get, but for the prototyping board, the ease of wiring resistors between holes 0.1″ apart may trump the extra robustness of laying them flat on the PC board.