Eeschema assumes all I'Cs are same supply, when not

Schematic
1

I’ve added screen shot to hopefully be understood. Simply put the IC’s on the screenshot are 2.5VDC and an NE555 which is on a different supply and no connection to the 2.5V rail.

EESchema places the 555 as part of the 2.5V rail accidentally picked up on PCBnew no errors or anything given. I have a 12v rail and 2.5V rail joined by a resistor.

The cct on the screen shot is trimmed down to simplify it.

2309×1338 124 KB

I can’t believe this is a bug for it’s a pretty bad one and if so, Imagine having had it auto-routed or had the PCB made without it being picked up.

Am I doing something wrong.

2

This is the bad NE555 symbol design. The only thing you may treat as “fail” (which is not) from KiCad Eeschema is to connect everything labelled VCC together.

BTW: Do not place wires which passing trough symbols body like you do for C13.

3

Ok, I have KC 4.0.5 and that’s the only NE555 symbol that shows up.

Ok, Need to remember! I changed the VCC on the 555 to +6V and added a power flag and it seems to have fixed the issue in PCBNew. Will check. I gather having first flagged the IC’s with 2.5V it took that as being VCC and not 12V.

For the hell of it I removed R18 the zeners resistor and added a 12V power symbol after the fuse. It has now changed VCC to 12V and I have a direct connection between 2.5 and 12V O’well seems like something important to remember.

Will do. Thanks.

4

One does not exclude the other. Remember that all symbols were designed and committed by users.

5

Ok, though I thought they would have gone through a review prior to being included.

Good to know. Thanks.

6

Sadly some of the symbol libraries are in a quite bad shape. (especially the symbols in the logic family libraries.)

If you want to look into modifying the symbols, in this topic i described a way to do it efficiently.
It is not as much work as you might think.
(I also described the finer details on how this “feature” you discovered works.)

1 Like