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RPI Home made hat

By bshabanov
Published in Electronics
June 24, 2020
2 min read

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.

Step 1: PCB Schematic

Photo by bshabanov
Schematic

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.

Step 2: PCB Milling

Photo by bshabanov
Milled PCB with 3018 CNC

For PCB milling I use a 30˚ angle bit with 0.1mm tip.

FlatCamp setup

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

Photo by bshabanov
Solder with Dremel Versa Tip

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

Photo by bshabanov
Terminal output from sensor

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.


Tags

#raspberry#home-automation#wifi-controller#ir
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