Reflow soldering SMT components¶

There are several surface mount (SMT) components in the kit. These should be soldered onto the board first before the through-hole components. For this step you will need solder paste and tweezers. We use a toaster oven for reflow soldering. If you are new to reflow soldering, there are online resources and tutorials.

Overview of steps¶

Place a small amount of solder paste onto the pads for the component you are working on
Use tweezers to pick up, place and align the component onto the solder paste
If necessary, use a magnifying lens to check the component placement on the board
Repeat steps for all components before reflow soldering
Once all of the components below are placed you can begin reflow soldering

Voltage divider resistors for the alphasense 4-electrode gas sensors¶

R1-R23 odd-numbered resistors (68K) and R2-R24 even-numbered resistors (20K) are paired. For example, R1 & R2 are paired, R3 & R4 etc. Each resistor pair is for one of the 12 analog inputs. The resistor pair form a voltage divider for scaling 0-5V sensor output to 0-1.2V analog input range (using 1.2V internal reference voltage).