Lanes of copper on a printed circuit board, for carrying current or signals between pads

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6
votes
1answer
121 views

Trace width and clearance calculations

What is the math behind traces and clearance calculations? I am designing a PCB, which will carry 12V and 6A, what should be trace width and trace clearance? Similarly, what should it be for 12V 3A, ...
8
votes
2answers
491 views

Is there any disadvantage to changing trace width in the middle of a trace?

Say I have a trace running across a board. It's 50 mils the majority of its length, but in one short place it narrows to 25 mils to make it through a tight area. As best I can tell, this will be ...
1
vote
1answer
85 views

Identify and replace a resistor [closed]

My APC UPS stopped working. I have had it for many years and it was serviced once by APC while in warranty and never opened again. Now since it is not in warranty anymore I opened it and saw two ...
0
votes
1answer
76 views

PCB etching from transparency

I wonder if someone could help me. A few days ago, my brother gave me all of his electronics, seeing that he doesn't need it anymore. I'm keen to learn electronics in depth and have basic knowledge ...
1
vote
2answers
132 views

Parasitic inductance of PCB tracks

For a PCB design, the longer the track length the greater the parasitic inductance right? But why would this be a concern if I'm working at low frequencies (e.g 50-60Hz) because it'll behave similar ...
3
votes
1answer
226 views

Are traces exiting a pad at an angle bad?

I have been told in the past that you should always have traces leaving a pad on a straight line. The reason I was given was that it could create an acid trap. From what I have read this is not ...
22
votes
4answers
3k views

How can PCB trace have 50 ohm impedance regardless of length and signal frequency?

Hmm, this seems to be just another question on line impedances. I understand that when we say "transmission line" effects we talk about things like cross talk, reflections and ringing (I guess that ...
3
votes
1answer
272 views

Are there any rules of thumb when computing pulse current ratings for PCB traces?

Say I have a surface PCB trace, 4 oz, 50 mils. That trace should be able to carry around 15 amps continuous, according a calculator I'm using. (Obviously your trace ampacity estimates may vary with ...
8
votes
5answers
509 views

Best way to test a high current pcb design 70A @ 12V

I designed a circuit (MOSFET HBRIDGE) that Should Be able to handle 70A @ 14V. Now that the board is sent out I am on to thinking about how to properly test it. Right now the most logical way I have ...
5
votes
2answers
178 views

What should be considered when sizing trace widths for digital logic signals?

For traces that carry a static DC current, it's pretty easy to calculate the minimum trace width based on the required ampacity of the trace. However, I'm not sure what should be considered when ...
3
votes
1answer
270 views

Power Plane and Decoupling Capacitors Routing

Forgive me for my simplicity. I'm just a hobbyist and not an engineer by trade. I am trying to make my first 4 layer PCB in Eagle and I have a question I cannot find the answer to regarding power ...
1
vote
3answers
200 views

11A trace width

Using this PCB Trace Width Calculator the external tace width for 11A (default settings) is suggested as 8.21mm. Is this acceptable? I was expecting something bigger, and just wanted to check that ...
2
votes
2answers
326 views

In Altium how do you increase the trace width from a Pour to GND Vias and Pads?

In my PCB layout I have a ground power connector and several pads where I would like thick traces to connect to the ground plane. When I use the polygon pour feature, it will connect these with 4 ...
4
votes
1answer
1k views

How to calculate parasitic capacitance in a trace?

I am given the equation for parasitic-capacitance as: \$ C = \dfrac{\epsilon_r \cdot \epsilon_0 \cdot L \cdot W }{ d }\$ I am also told my trace is to be 1000 micrometers long (1mm) and 45nm wide. ...
7
votes
3answers
3k views

How to make traces on an universal PCB?

I hope this question won't be closed as too subjective. I'd like to know best practice - how to make traces on universal PCB's with individual holes without traces (like the following image). My idea ...
1
vote
1answer
134 views

SDRAM on opposite side of board with respect to uC

Just a quick question. Is it advised against to place a high speed memory device on the opposite side of the PCB with respect to the microcontroller? And if it is ill advised, how is it possible to ...
4
votes
2answers
430 views

Why Altium routes trace to the side of the pad?

I am curious, are there any reasons why Altium tends to route a trace to the side of a pad, instead of the top? The top looks more logical, since it will not disturb other traces in a SOIC for ...
4
votes
1answer
266 views

Trace width to 0805 pad?

How worried should I be if I route wider than 10 mil trace to 0805 pad? Would 16, 20 or 24 mil trace cause soldering problems without making 10 mil neck?
5
votes
2answers
231 views

Satisfactory Margin for Traces from PCB Edge

I've had problems routing too close to the edge of a PCB before and was wondering if there's a suitable rule-of-thumb that I should use (maybe to put in a design rule in Altium somehow with my ...
0
votes
1answer
418 views

How do you adjust the trace rotation on a Hameg HM 307?

I have a [rather old] Hameg HM 307 oscilloscope with the trace rotation slightly off. There is no trace rotation adjuster anywhere on the outside of the device. The user manual mentions that it is ...
2
votes
3answers
760 views

Repairing broken trace on commercial board

A friend has a USB flash drive on which the SMD USB connector broke off. When it broke, it pulled the pad traces off the board with the solder. We are trying to think of a way to reconnect the ...
3
votes
3answers
1k views

How to measure propagation velocity through a trace on a pcb?

With a pcb in hand, how to measure the propagation velocity of a path from point A to point B, with accuracy in the picoseconds range?
1
vote
1answer
181 views

Unoccupied SMD and TH pads and noise/interference/capacitance

Imagine a rather noise sensetive application, My question is if there are unoccopied pads for SMD and through-hole are existing on the board and somehow connected to other components through theire ...
2
votes
2answers
400 views

How to calculate typical signal trace clearance?

Knowing nothing more than most of the signal traces on a project are 7.5mil and it's a high end audio product, i.e. it's not a high frequency or any 'advanced' application, what would be a safe ...
2
votes
3answers
2k views

Eagle Schematic and Board layout design for simple opamp module questions

Hopefully I'm not doing anything illegal, I posted a very similar question a few days ago, but this one is different. Here is what I've been working on the past couple days, trying out different ...
12
votes
4answers
2k views

When laying out circuit board traces, what impedances do i need to consider?

I do low-speed circuit design for microcontrollers and such (usually <20MHz) and now I'm getting started on some more high-speed circuits. What I want to know is: What considerations need to be ...
4
votes
2answers
459 views

LM13700 Question

I'm currently troubleshooting a state-variable filter I built. All of the filter types work, but the resonance pot has no effect. Tracing a sine signal through the feedback pathway, I found that it ...