Below is a picture of my first-ever PCB that I've tried to get actually made. This holds three All Sensors Corp. pressure sensors, one 6-pin BMP280 breakout board, and one TC9548A 1-to-8 I2C multiplexer. Along with a bunch of pullup resistors and some capacitors on the power inputs. It has one I2C+power input, and one I2C+power output to an off-board temperature sensor breakout board that I would screw to the outside of my probe.
The cost to get 3 of these made at http://oshpark.com/ was just over $20, including free shipping. This work is not on the critical path of any testing at this point. The goals are:
- Go through the schematic -> board -> production process.
- See what a board looks like in person, and compare it to my design.
- Determine how my traces went -- any places where wires are too close?
- Show to an experienced friend and get feedback.
- Go through it with a multimeter and look for wiring mistakes.
- Buy some SMD parts and practice stuffing the board.
- With the board partially populated (without soldering in the really expensive All Sensors chips), determine if it actually works.
- Get some DIP headers and attach one of the All Sensors pressure sensors, and see if it works.
I'd be pretty surprised if all of these steps went well, but we'll see.
In general, the long-term goal is that I'm trying to develop and "in house" capacity to build PCBs since this will quickly become my limiting factor. I need to be able to miniaturize my work so as to make it (especially the probes) really lightweight, which in turn will make the probe mounting simpler and easier (if it's no heavier than a GoPro, then any little GoPro mount ought to work).