I’m planning to build a Gas Chromatograph with an Arduino, I’ve copied Marb’s lab schematic for now and plan to add a couple of detectors in addition to the MQ-2 gas sensor and the thermal conductivity sensor.
I started by replicating Marb’s Lab layout just to get going, but since I’ve only just started using KiCad, I’m running into a few issues.
First: How do I make this black wire with the circle?
And I assume the “+1.25 to +2.5V” is just a comment.
Second: How do I make the connections between the Conn_01x02 on both sides?
You can see on the schematic that the green wires on the right go into the connector, but I’m not sure if they’re actually connected. When I try it myself, I can only get it connected on the red connector.
I’m not using KiCad library so each symbol I have at my schematics I just define myself.
I would search for something like this as testing point.
Remember that KiCad is PCB design tool so generally what you have at schematic is what you want to have at PCB. I suppose that at PCB you need only connection to J2 socket. The bulb is probably just inserted in socket so the wires here only shows that bulb belongs to this socket and as these wires need not to be routed at PCB their connection with anything at PCB is not needed.
First: That is a Directive Label, used to assign net classes to different nets of your circuit. They don’t connect two nets each other, but only assign the type. For example you can have a Power class add it to all voltage rails in your schematic.
Find this option on the right-side panel of KiCad.
Second: Shown in that video is a weird way of connecting other symbols to a 2-pin connector. It is not recommended to do it such a way. Instead, simply connect the lamp directly to the pins or wires where you can clearly see the junctions formed.
When replicating a schematic, it is always good idea to improve up on it, instead of replicating all mistakes and weirdness. Design for readability and clarity.
J1 is the socket on the PCB. J2 is the plug and is attached to the lamp LA1. J2 and LA1 are not part of the PCB but are in the schematic for clarity. J2 & LA1 should be marked as “Do not populate” (see J5 & J6 & LA2). Same for the three pin plugs and sockets J2 & J4.
To mark these as Do Not Populate (DNP) open Properties of each symbol and go to Attributes. Tick the DNP box.
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These plug/socket combinations can be found in the top connector library in the Kicad library list.
Alright! I’m going to do this, it looks way more comprehensive than using a generic connector.
Something I forgot to mention: in the original schematic, we can see that the 12V mini air pump has 3 pins. However, in KiCad, the only one I can find has 2 pins. Here is my question: should I create a new component for this 3-pin motor, like I did with the MQ-2 sensor, or should I download it from a library?
I guess for a simple component like this one, which, as you mentioned, won’t be on the PCB (it will be marked as DNP) it’s not a big deal. But I’m asking for future me, in case I run into something more complex later on in the project and want to make clear documentation.
Unless you will need a 3 pin motor a lot in the future, it is easiest to place the 2 pin motor on the schematic and edit that.
To Edit:
RMB click on the motor and “Open with Symbol Editor” (or Ctrl + E).
Place Pin, give pin a number, Save.
Done.
