Track Width Help!

Hello all I have a question. As stated before I’m no engineer by any means what so ever and am doing this as just more of a hobby, so in turn I really don’t know much about watts, amps, and voltages for pcb track widths to make sure I don’t burn my house down or fry a board. I’m wanting to make my project as near as complete as I can before I have any boards made up for prototyping.

Anyways back to my question. I know my supply voltage is going to be about 5v for my project. This project has 2 boards that connect to each other via a 2 pin power cable. 1 Board has 1 5v power coming in and 1 5v power coming out to then be connected to the 2nd board via the power cable in between the 2 boards. The second board only has 1 5v coming in. I’m not sure on how to calculate my track width to be able to make sure I don’t burn my house down or fry the board. I don’t have the wattage or the amperage of the system its getting put into. I know with ohms law you have to have at least 2 of the 3 to calculate for what your needing in your application.

Let me know and like I said I’m really new to this and I’m by no means an electrical engineer. I just was wanting to try to learn something new and get a few ideas for things I have stuck up in my head while I’m stuck at home and can’t work because of my broken leg for the next 2 months.

Thanks again all and have an awesome day!!!

At least on Linux KiCAD comes with a PCB Calculator wich may be of use to you.

On windows i used to use this toolkit.

A general advice from me would be to always get your power sources as low of impedance as you can. Regardless if GND or whatever voltage rail, it is almost always a good idea to poor a plane on one layer completely with those voltages or get at least the tracks as wide as you can get.

You ask a very relevant question which does not have an easy answer. A dwelling conflagration is certainly one failure mode but a device or system may experience reduced performance due to voltage drops, inductance, capacitance, or stray coupling in the power distribution circuitry. Regulatory compliance or certifications may also affect design decisions. There are numerous online suggestions, and calculator tools (such as the one supplied with KiCAD), each with a particular set of assumptions and criteria.

For common household applications in benign operating environments it’s commonly believed that a 10 mil wide trace of 1 oz copper will reliably carry currents of 750 - 1000 mA. This is based on copper fusing and trace delamination, not voltage drops over long trace runs.

In your situation you will have to make some reasonable guesses about the current involved. If you don’t know (and can’t estimate) the maximum current draw of your system, consider the capability of its power supply. A wall-wart power supply equipped with a barrel jack isn’t likely to provide more than a few amps of current. A “brick” module might get as high as a couple dozen amps. If your system will charge massive battery banks, or jump-start a locomotive, this Forum probably isn’t the place to ask for advice.

(As a side note, batteries can be deceptive. A common AA alkaline cell can provide 15 - 20 amps of current for a few minutes. Modern lithium cells can do more than that. Consider this when you design traces or wiring on the battery-side of a disconnect device or protective circuitry.)


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My build is using an power adapter that’s already inside the unit, I’m just using a wire split adapter that has 12 v and a 5 v lead with 2 grounds, 1 for the 12v and 1 for the 5v. So power supplied is within the unit the circuit is going into. There’s no battery’s in this build. Idk if this helps or not but I’ll try to supply as much information I can.

Has this supply a specification or model number? What kind of supply is it? Is there a Datasheet / reference for it?

What’s the 12V for and how are you using it? Is the 12V the input or a second output?
can you maybe supply us with a drawing on how you plan to connect things?
Without having at least the specification of your supply and how you are planning to use it, it is impossible to give you any good advice.

If you will use too thin track and it will burn itself it will not burn your house but rather protect it from being burned by something in your circuit consuming too much power - it will work like a fuse.
Long time ago reading something like you have written I would not suppose any computation power is contained in the circuit we are speaking about, but nowadays I have to consider it. Specially that you are using 5V. If there are any microprocessors in what you design then you can get into trouble if your 5V cable is too long. I can’t figure out from your info if it is 3cm connection between boards in the same box or 10m connection from house to gate.
In my childhood (was about 12) I have done voice connection from me to my friend living 2 floors down and not directly under me. It was first time I bumped with voltage drops at cables

For my build its a molex cable that goes inside an xbox original. I using a splitter off the power cable for the hard drive power to my build. But for my build I’m working on I’m not interested in the 12v supply but more towards the 5v supply. The 5v supply will be powering both circuits that I have designed with a jumper wire for power from one board to the other. I can’t find a specific model number on the power supply it self but its a power supply from an old xbox original console.

My build will not have any computing power period in it. It will house a few power connections, resistors, and a few leds is all. In between boards its about a 6 inch connecting wire to attach both of the boards to the same power supply.

So there are no elements which work can be disturbed by disturbance :slight_smile:
Typical signalling LED (not lighting) consumed 20mA 30 years ago, and now I’m using such that 1…2mA is enough for them. In such current levels you can use even the thinner track you are able to do. But as I expect you have a lot of free space at your PCB so use for example 1mm tracks.

Yeah theres nothing in the way as far as disturbance just a simple led board as a fun little starter project, but my next project is a little more involved so I’ll probably be back with more questions on that one lol. Yes there is a lot of space open on my board. I’ll try the 1mm tracks and see how that goes. Thanks for the help everyone.

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