Earlier today I got the PCB’s for my weather station controller, and while it isn’t perfect, it is absolutely usable. But in an attempt to make it as perfect as I can, I am trying to make some kind of system of what went wrong, and what I am going to do about it.
So let’s put a PCB under a microscope, literally.
Component names missing
Text for status leds too small
Width of text on backside too thin
Holes for relays only just fit
Unstable voltage after the 3v3 voltage regulator
Missing 10kΩ pull-up resistor for the anemometer
Unstable connections in the SD card connector
1. Component names missing
Check if the names are on a wrong layer, or if it didn’t get included when going from Eagle 6.5.0 to 7.0.0
Conclusion: Text smaller than iTead could print, so they removed it without notifying me. Text size increased from 0.4064 to 0.8
2. Text for status leds too small
Move led’s down about 1mm to allow the text to be a bit bigger, keep ratio as it is.
Conclusion: Leds and resistors moved 1mm down to allow text size to go from 0.8128 to 1.05
3. Width of text on backside too thin
Increase text ratio, there should be plenty of room to do that without any other changes.
Conclusion: Text ratio increased from 8% to 12%
4. Holes for relays only just fit
Increase hole size by 0.1mm, that should be enough to make the relays just fall into place.
Conclusion: Hole size increased by 0.1mm so they now are 0.7mm in diameter.
5. Unstable voltage after the 3v3 voltage regulator
Adding more decoupling capacitors after the voltage regulator should stabilize it while the Impee is transmitting and spiking on current usage.
Conclusion: Removing the 1uF capacitor and replaces it by 3 pieces of 10uF capacitors instead.
6. Missing 10kΩ pull-up resistor for the anemometer
Added a resistor to the rain gauge instead of the anemometer.
Conclusion: Leaving the 10kΩ on the rain gauge, and disabling the internal pull-up in the Impee. Adding a 10kΩ resistor to the anemometer. Improved the 3v3 trace from decoupling capacitors to the Impee while doing so.
7. Unstable connections in the SD card connector
Analog readings from sensors was unstable and at times didn’t make sense at all.
Conclusion: Crap connectors from china are replaced with connectors from Amphenol (101-00313-68-02)
While there is a lack of quality on the silk screen, there isn’t really anything to point at on the traces.
Here we got the traces going from the sd card connector, and out to the two RJ11 connectors for the weather sensors. The two pads in the middle of the picture is for a 10kΩ 0805 pull-up resistor.
The vias are looking pretty good too.
Here we got the ones for the status leds along with the resistor needed for those.
The holes for the through-hole components look just fine too.
A few of them look a bit off center, but nothing worrying at all.