This document says, “This table helps finding the minimum clearance between conductors. Each line of the table has a minimum recomended distance between conductors for a given voltage (DC or AC peaks) range. If you need the values for voltages higher than 500V, enter the value in the box in the left corner and press Update Values.”
I am currently designing an audio amplifier with KiCad7.
The power supply for the board I am making this time is ±17V.
The document says “DC or AC peaks,” but does this mean the peak to peak value of AC?
The power supply for the board I am making this time is ±17V, so should I assume the power supply is 34V?
The board is a two-layer board with through holes.
The location is at an altitude of less than 1000m.
So would that be “conductor spacing 0.6mm” in the “B2 31V to 50V” column?
I have never used this and don’t know where from these values come (some safety standard ?).
In my opinion distance between tracks depends on maximum voltage between them and it is not a common for the whole PCB but can be different for each track pair. So if at your PCB you have a track connected to base of npn having emitter connected to GND than to find distance between this track and GND you should use 0.7V. If you have track that is close to +17 and other close to -17 then if they happened to be next to each other then 34V should be used.
It is not so, that if at one PCB end you have AC230 trafo then on the other PCB end you have to keep distances between all tracks that you count from 230 * SQRT(2) voltage.
Piotr, sorry to keep you waiting.
I have one question.
Does the minimum distance between conductors depend on the voltage and not the current?
If so, is there a table of voltage vs. minimum distance between conductors?
If so, please let me know.
These calculator tools can calculate track width (dependent on current and temperature rise) and there is a (standardized) table for clearances, see screenshot below:
paulvdh, thank you for your answer.
I asked about the “conductor spacing” in KiCad’s “Calculator Tools” from the beginning. However, Piotr said that “Calculator Tools” and safety standards are not necessary, and that conductor spacing is determined by voltage, not current.
I’ve looked into this in various ways, but I still don’t understand it.
I read too many posts here, and my attention sometimes (euhm, quite often unfortunately) wavers a bit.
This question confuses me a bit:
What is your overall electronics knowledge? That question should be quite easy to answer even by someone with not very much experience in electronics. Also, if you look at the Electrical Spacing table, then you also see it’s based on voltage, and not on current.
Such tables are made for electrical safety, and therefore, you take the maximum voltage that can ever occur between any two nets on the PCB.
I also do not know whether the voltages that you mention:
Are DC, AC RMS or peak to peak.
And the voltages are also relative. Voltages are always relative, you always need two wires of your multimeter to measure a voltage difference between two points. You then take the maximum voltage that can can occur between two nets. So if one net is 17Vdc, and the other net is 25Vdc, (both referenced to GND, then the difference is only 8V.
If you are dealing with AC voltages, then you take the maximum voltage that can occur during any moment. Maybe the AC voltages are always in phase, maybe one power supply starts quicker then the other. There are lots of little details that can influence what the maximum voltage between two nets can be.
minimum distance between conductors is a voltage, pollution, , substrate, coating and altitude concern.
The larger the voltage differential between conductors → the larger the separation
The higher the pollution consideration → the larger the separation
The lower the coating capability → the larger the separation
the lower the substrate capability (FR4) → the larger the (z) separation
The higher the altitude → the larger the separation
IPC2221 and BSEN60664-1 are reasonable guidelines to determine the separation and both sets of calculators are included within Kicad calculator
Current handling drives track thickness (xy and z)
paulvdh, thank you for your reply.
I have a lot of electronics knowledge that I need to relearn.
I calculated the wiring width using KiCad’s Calculator Tools, and the result is shown below.
However, when I emailed Fusion PCB, which I will be using to manufacture the board, they told me that the wiring width is basically said to be 1A = 1mm, so I should think of it as 2A = 2mm. I also think that the conductor spacing should be the same as the wiring width, so 2mm would be good. The reason is that the larger the wiring width and conductor spacing, the better, and 2mm is appropriate given the size of the board and the number of components.
If you do that, there will be a significant difference from the calculation value of KiCad’s Calculator Tools. I wanted to ask if it’s okay to have a difference and also the reason.
Naib, thank you for your reply.
1 oz/ft² (about 35µm) can support a current of about 1.5A to 2A, so I calculated using 1 ounce this time.
For this board production, I will use FR-4 T130G material.
I understand that the greater the voltage difference between the conductors, the wider the spacing will be.
I will use a leaded solder leveler for surface treatment.
Thank you for your reply, jmk.
I have a question about how to use KiCad’s calculator tools.
I asked the question because there is a big difference between the values calculated by KiCad’s calculator tools and the trace width and conductor spacing recommended by Fusion PCB.
As I have said. I have never used KiCad Calculator so I based on what you said and in your first post you said:
So.
First you said about distance depending on Voltage.
Then I have said also about distance depending on Voltage.
And then you ask if distance depends on Voltage why we all the time are speaking about Voltage.
And then you ask about table for distance versus voltage while you have written about such table in your first post. Did you forgot it?
In popular language (here in Poland) people say that there is a current in AC 230 sockets. While until you not connect anything to it there is only voltage and no current.
Simply getting electric power to house is said as getting current.
May be in some place you were suggested by using such wording or may be you have to use translator and this translator in some place used popular (not technical) language. I don’t know how it is in English popular speaking.
Here is your mistake.
For VCC 5V/2A you can use 2mm track (but I would prefer wider track) and 0.2mm distance to the GND next to it.
2A needs wide track to not make it too hot.
5V will not generate spark over 0.2mm distance.
Really?
Learn to use the calculator tools and stand on your own legs.
We’re happy to help others and give them some guidance into the right direction but if we keep on giving answers to such trivial things then this will keep on soaking up ever more of our time. The calculator tools have been mentioned several times in this thread. Now study them a bit and learn to use them.
Where in the calculator tools is there a tool that will calculate conductor spacing for 17V2A? I’m using a translator so maybe I’m not very clear, but you all have no right to make me sound like I’m asking a bad question.
Clearance between tracks (Depending on voltage) has already been shown by screenshots.
Track with (for the current) has it’s separate page in the calculator tools. It is an interactive page and you can type in some numbers, and KiCad calculates the rest.
Current has nothing to conductor spacing (clearance). So forget 2A and think only about 17V.
I don’t know those standards (IPC… IEC…) mentioned in KiCad calculator, but these are probably safety standards. Safety applies if there is a risk of electric shock to humans.
If you need not to consider such risk (human can’t touch with finger your tracks) you need not to follow these standards requirements.
I typically (for up to 12V at my PCB) use 0.2mm clearance and for circuits having up to 30V I use 0.4mm clearance. But I don’t know if there are something that needs from you to apply some standard.
Imagine that you use translator to get your post translated into something like we see at his screenshots.
Even if someone will told you that in translated text you should replace conductor spacing with clearance next time translator will use once more conductor spacing (may be expressed with another sign) and you will be may be not able to be sure which signs you have to replace with which to not make it being less understandable.
