week 08: Electronics Design¶
Summary¶
This week we learned the very basics of electronics design. For planning out the board we used Eagle.
The Theory¶
In Eagle first the Schematic is defined and can be later used to generate the board. We added two Libraries, over the Library Manager with parts that later could be used more easily, when it comes to assembling everything.
The Library Manager
The Schematic Editor¶
Above are some of the most important tools are shown. From left to right:
Selection Tool: For selecting a group of objects and performing some kind of transformation on them
Transformation Tools: For Moving, Mirroring and Rotating the parts
Add Part: (on the right) For adding a part from the libraries
Netting Tools: For connecting the parts, creating junctions and labeling. The labels with the same name get connected automatically.
Naming Tools: For naming the parts or the labels
The Board Editor¶
The board can be generated by clicking on the “switch to”(
) icon.
At first some constraints can be set in the Design Rule Checker e.g. a clearance of 17mil and a width of 12mil. There are similar tools available like in the schematics editor. Some additional ones are:
Route Airwire & Ripup: to add and remove wiring
Ratsnest: For displaying the most direct connection from one point to another
Polygon: Can be later used to draw a shape around the circuit
The Design¶
Schematic¶
I decided to expand the board that got layed out in the lecture.
The parts I added are pins for all the sensors (temperature sensor, LDR, soil moisture sensor) I would like to include in my final project and an option to power everything with a battery.
The pins for the LDR, the Temperatur sensor, the soil moisture sensor and the LED matrix
Since both the LDR and the temperature sensors need resistors I added them here too. For the LDR I used the same setup as in week 06 and the setup for the temperature sensor can be found here >> (page 7).
After that I setup two pins to plug an battery to. Since it’s usually 9V that are coming from the battery, it has to be regulated to 5V. The row of three pins is intended for the regulator.
Battery and voltage regulator setup
So I ended up with this Layout:
Finished Schematic
Board¶
When the board is generated the parts will land at the bottom of the workspace. They can be rearranged loosley and ratsnest can be performed, to connect the shortest paths.
Loosley arranged parts
Now everything has to get connected. Parts that can connected between each other light up, when clicking on them with the routing tool:
Highlighted parts
I had to rearrange some parts in the schematic again.
First I split the pins for the LED matrix in two so I could route a connection, I didn’t had place for beforhand, inbetween.
Splitted LED matrix pins, schematic and board
Another thing I had to add, was a 0 Ohm resistor to bridge a connection.
The problematic airwire
The bridging option
Lastly I surrounded the circuit with a polygon, assigned GND as a signal and another ratsnest would fill the blank spots in.
Filled in polygon
So the only thing left is to export is as a monochrome image
All layers, except top and pads in the Visible Layers menu and the displaying of the remaining names get disabled.
Layer visibility menu
The image can be exported via file > export > image
Export menu
So here’s the result:
Exported image
And the whole schematic