Fast wire draw mode already available EESCHEMA!

Playing around with Eeschema today I noticed that KiCad already supports a fast wire draw mode that I just saw the other day in a training video for Q-Spice by Mike Engelhardt. Mike demonstrates this feature in the above video at 4:36: When you have placed your resistors and capacitors you can just run over them with a wire. Q-Spice will automatically break them at the pins of the symbols. This really speeds up schematic entry.

The same technique is also available in KiCad for simple 2 pin components:
If the pins are oriented in one line you can run a single wire over multiple components. When you complete this wire Eeschema will automatically break the wire at the components, creating multiple nets.

But this only seems to work for simple (2pin) components. If you run over the Collector and Emitter pins of a BJT, or through the pins of an IC Eeschema will make a connection at each pin crossed by the wire, but it will not split the nets. Q-Spice will connect the pins, but break the wire, creating multiple nets.


I did not know this was implemented in KiCad. But after checking in V7.0.10 it does indeed work for resistors, capacitors and diodes, maybe for other two pin parts too. It also works the other way. If you have a wire, and then place a resistor on top of it, then KiCad removes the wire section between the two resistor pins.

I guess the goal is not making schematics draw quicker, but more preventing mistakes by shorting out parts. A wire drawn over a diode is not visible, except for the junction dots on the pins of the diode.

There are also cases when wires are drawn over schematic symbols on purpose. I’ve seen others do this, and I have also used it in one of my own designs. See for example the design below. It is a design for a passive backplane. It has one custom schematic symbol which has all the signal names (This symbol is also used in other projects) and the other connectors are just generic default connectors, which have the same footprint type assigned. This schematic was extremely simple to draw in this way. (Just put a connector on top of another one, then drag it aside and KiCad adds all the wires for you). Doing this with a bus and labels would have been cumbersome, because the signal names have changed several times during the design. The way it’s drawn now, it’s obvious all connectors have the same wiring.

It’s nice to have such “auto” functions. But if they have unintended side effects they get really annoying very quickly. Suppose you wanted to short a resistor out for some reason but KiCad won’t let you draw it in a schematic? It is (still possible to draw a wire though a resistor between it’s pins when you draw the wire directly from pin to pin).

Apparently it works this way for all two pin symbols. In the example below, I drew a single wire over all the schematic symbols shown. The wire is cut on the two pin connector, but the pins of the 3 pin connector are shorted together.

Your point in generating bus planes by running a wire through all the connectors is really an interesting application that would make a good use of the autoconnecting feature.
Configuring how KiCad behaves on Symbols with more that 2pins will truly make things messy.

For shorting out parts:
As you have mentioned running a wire through a diode symbol would not be visible, thus error prone.
Also I would never try to run a wire through a resistor to short it out. It looks like a fuse and also can get overlooked easily.

Shorting out resistors can be done like this:

which btw. can be seen quite often on T-shirts here in Germany :rofl: :rofl: