I have a Raspberry Pi 3B+, and I use it for simple home automation like controlling the TV, AC, and some lights. Recently I bought a cheap Chinese CNC router and started to make simple PCBs. (I want to point that I am an absolute beginner in electronics so there might be some mistakes).
One of the first ideas I had was to build a board for the RPi that has a temperature sensor and IR LED. So this tutorial is about what tools I have used to accomplish this idea.
The schematic is very simple, the Si7020 use i2c protocol, so it must be connected to pin 3 and 5 on RPi, the fan must be connected to pin 2 or 4 and all other components can be assigned at different pins. Currently, I use these pins because for me it was the simplest way to design the traces for the PCB.
It is important to say that when I add a component(or make trace) in the PCB design I always make this component pads at least 0.6mm. For example, if the pad is with size 0.6x0.4mm I make it 0.6x0.6 and this is because my CNC is unable to make it smaller without cutting too much.
For PCB milling I use a 30˚ angle bit with 0.1mm tip.
For traces cutout
Tool Diameter: 0.13 Type V. The “Cut Z” should be -0.06mm. Enable Multi-Depth with value: 0.03 Travel Z: 1.2 Spindle speed: 8000(this is maxed value for my DC motor) For holes drill and board cutout
Cut Z: -1.501 *I use 1.5mm F4 PCB so this value should be changed according to your PCB thickness. Travel Z: 1.2 Spindle speed: 8000(this is maxed value for my DC motor) I left all other settings unchanged:
Feed Rate X-Y: 80 Feed Rate Z: 80 bCNC setup
Before start milling, I run auto level and I aways set X-Y steps for probing to be maximum 3mm.
##Step 3: Soldering
For soldering, I use Dremel Versatip which can be used as a hot air gun or soldering iron.
First I start with the iron tip. I apply flux to every pad I will use(the brown and black spots on the PCB in the image gallery are flux). After that, I apply a very little amount of tin. Then I switch to a hot air gun, position the components on their places, and start heating them.
##Step 5: Run and Useful Links
For IR LED I use Lirc and for the sensor, I wrote a little python script.
As you can see the temperature measured by the sensor is 31˚. The actual temp is the room was 24˚. The difference comes from the RPi temp, which is 45˚ with the fan running. So when I return the measured temperature from the sensor, I subtract “7˚”, and the returned value is pretty accurate.