I am newbie to KICAD, while trying to use a shunt resistor, I found that there’s no shunt resistor available that has 4 pins, I only a resistor with 2 pins is available, so there’s no way to connect 4 pins on it. When trying to connect 4 wires to that resistor on the PCB and choosing the right footpring in the assign footprint section, I finish with having only two wires connected to the shunt! while the measuring wires are not connected, which is normal since I have only 2 pins! Please, see the images below to understand the problem:
My symbol is the same as R_Shunt above.
Listed in the Clearance Overrides and Settings tab
I have two net-ties:
1,2 - pins 1 and 2 may short
3,4 - pins 3 and 4 may short
I am guessing that these 4- wire SMT shunts are going to be deprecated over time.
I guess that using a two wire resistor, combined with net ties tied the right part of the resistors are a better option. I have even seen teardowns of Keithley measurement equipment, in which 4 wire shunt resistors are used, but the sense pads are shorted to the power pads by the pads on the PCB. The blob of solder on the pad is a very good conductor, and it may be more stable then the connection on the SMT resistor itself.
But it’s a guess. I am curious about some real life measurement data for this.
The parts I use are short and wide two terminal resistors, almost a small metal bar. I have 0.003 Ohms as a sense and it works, I have designed PSUs where the sense pins go to the AD controller IC as a differential pair and the current limit is very close to the designed value. Using these values allows me to get remarkable efficiency in the high 90s%
From your pictures (at your first post) it looks that you have 4 pad footprint for your resistor.
To use this you have to use 4 pin resistor symbol and you need not to even consider using of net-tie.
If there is no 4 pin resistor symbol just made your own (I am using only symbols and footprints from my libraries to be not surprised by any changes in KiCad libraries). Editing symbols and footprints is much, much simpler than designing PCB (you can use KiCad libraries to copy symbol/footprint from there and edit it for you).
Only with making your own libraries for first time you can have some problems, but I believe it is described in FAQs (top of forum window).
Net-tie is helpful if you use standard 2 pad resistor as shunt resistor and you want to separate tracks like it is naturally with 4 pad resistors.
When you have written your first post you didn’t know that this symbol exists. Instead of searching it you could (not have to, but could) just do it.
To have printed documentation taking as less space at my shelf as possible I prefer to have single page schematics. Since I started to use KiCad in 2017 I had never to use multi-sheet schematic. Partially it is because I use my own symbols that are smaller than KiCad symbols.
So: you don’t have to, but I definitely prefer to.
Sorry but I did not mean to bother you. Me neither, I just realized that there’s another library other than the standard one where we can choose different components type! Thank you anyways!
