Original page created on 19/03/2020.
Preparation for circuit design
Associate the device footprints
It is a matter of indicating which real devices will be associated with the symbols of the diagram.
The following window is quite confusing:
Indeed, the three columns are not in an obvious order. On the left, the list of footprint libraries. On the right, that of the devices of the selected library. And in the middle (why?), that of the devices of my diagram.
The game consists, for each kind of device, of selecting them in the middle, of going to the left to find the correct library, then to the right the desired footprint. How to validate the choice? You have to double-click on the footprint!
Example here with the resistors again. I need a 1206 size SMD footprint (not too small, not too difficult to solder).
- Select the resistors of the same footprint.
- Scroll through the list on the left until I find the Resistor_SMD library.
- Select the desired footprint from the list on the right, and double-click.
Simple, right?
The same goes for the other devices, provided you find a footprint. This is not the case with reed switches. I’ll have to create one!
Create a footprint
For my reed switch, a through-hole device, I chose a pitch of 19.05 mm, or 0.75”. I’m not going to create a footprint from scratch: I’m looking for an existing footprint. Given the pitch chosen, a large rectangular capacitor should be convenient.
Another list! The through-hole devices are called THT.
This one seems pretty good to me. Translation of the name: L = length of 19 mm, W = width of 5 mm, P = pitch of 15 mm. A little too short, but the next one is too long. We will adapt…
Here it is.
Its pitch is too small. So I move the 2nd pad. How much? Well, from 15 to 19.05. To do this precisely:
- Click the pad;
- Right click to display the context menu;
- Choose Move Exactly;
- Enter the desired value, i.e. 4.05 mm.
The most important thing is done, but you also have to modify the outline. For that, I can move lines or stretch them, by pointing their end. I don’t know exactly what all these lines are used for, except those of the layer F.SilkS (F for Front side; SilkS for Silk Screen, for drawing the devices), but I modify them all, in case. It is also possible to type numeric values in an editing window. Click the line to edit, type E for Edit (Properties in the context menu):
We must also change the name. Click the text, E for Edit:
Just type in the new name. Here it is:
Note that only the blue graphics will appear on the actual printed circuit (layer F.SilkS).
It remains to save the new footprint. It is better to create a new personal library (ma_bib here). I do File / Save as… and I enter the new name.
Let’s go back to the footprint assignment list
Don’t forget to click the Apply button, the only click on OK would have no effect for the rest!
Creation of the netlist
This list is essential for establishing the correspondence between the diagram and the PCB itself.
Just click Generate Netlist, then Close.
This time we are ready to start the circuit itself.