Assembly
Assembling this board starts with the two surface mount parts, the INA226 and the current sense resistor. I tinned the pads with an iron and then reflowed the two parts in my reflow oven. It certainly felt like overkill for two parts but I have the oven so I use it whenever I can.
If you don’t have a reflow setup then it’s not difficult to do these two parts by hand with an iron if you have plenty of flux, good light and some hands-free magnification. There are many tutorials and videos on YouTube about how to hand-solder SMD parts.
After the two SMD parts are done it’s on to the simple but time-consuming task of bending, inserting, soldering and trimming the through-hole parts. It’s best to do these starting with the lowest profile resistors first and working up to the tallest parts. That way when you turn the board upside down to solder a part it will be held in place whilst you work by its own contact with your work surface.
Finally after a fairly long but strangely therapeutic soldering session it’s all done.
I know I’ve said it before but I do like the look of a project built with through-hole parts. It’s certainly a marvel to inspect a densely packed SMD board but the look of a through-hole project with all those chunky bits on it appeals more to me. Next I’ll insert the NXA66 into the edge connector and build up the temperature sensor cable.
I made a cable for the temperature sensor out of a cheap 3-pin computer fan cable that I got on ebay. The connector on the other end was snipped off and the resulting wire ends were soldered to the MCP9700 TO-92 leads. The fan’s not fitted in these photographs. I’m still waiting for that to be delivered. Hopefully it’ll be ready by the time I shoot the video that’ll accompany this article.
I used some heat-shrink tube to insulate the legs of the TO-92 and then kapton taped it to the back of the heatsink where I can see that it makes contact on the other side with the power MOSFET. This should be the hottest part of the heatsink and therefore the best place to take measurements.
