So I’ve gathered there’s an electrical reason for this in some contexts, IIRC EMF noise cancellation for high speed digital signals?
How widely does this effect have relevance? Doesn’t seem to be a thing in analog world, where shielded coax seems to be the go… Anyone know why that is, out of curiosity?
But my main question - is there any reason not to twist, or even plait wires? It’s a bit of a habit when I feel inclined to tidy up the guts of something, but sometimes I’ve wondered if I might be making problems.
Twisting wires is perfect for differential pair signals, like ethernet, USB, CAN bus etc.
But this noise rejection is only effective if it is common between both data lines.
Where you want to keep the signal as intact as possible and only read the voltage output, your best bet it to try and protect the signal as much as possible (shielding).
If you have digital signals, or power supplying wires next to a sensitive analog signal you can induce noise into that cable.
It might also make the project less servicable, discouraging you to fix it.
But on the other hand… a neat wire harness is unbeatable.
There is. It is to do with interference rejection for one. The main reason however it help prevent radiation from these wires. This works in reverse too. It will prevent unwanted signals impinging on this cable. The twisting cancels out these problems. That is why the old balanced TV line ws twisted. You want only the signals at the antenna not the spurious interfering signals on the transmission line. Also in the transmitter case you only want the radiation from the antenna, not the transmission line.This type of line is less lossy than co-ax but with the development of better amplifiers etc it fell by the wayside. Open wire balanced line is still used where co-ax loss would be unacceptable.
On the contrary this is where you will find most of this. Think Telephone cable, any audio cable is another prime example, particularly for long runs and microphones. Also have a close look at high voltage power transmission lines. Every so often you will see 2 of the wires crossing over. Most easily done where the line changes direction. This could be considered as a type of twisted pair although I think the prime objective here is to prevent a voltage build up in one wire due to capacitive coupling.
Yes. Where you WANT the wire to pick up or radiate a signal.
Care should prevail here. Although it looks tidy problems can arise if larger currents are involved, even in earth connections. Balanced twisted pairs or screened circuits should be OK.
You should refer to Liam’s link. This can be applied to RF as well as in open wire balanced transmission lines between transmitter and antenna, often with a Balun at each end. Often that is a bit of a black art so just believing it does work is the easiest path.
Cheers Bob
Overhead telephone and telegraph wires had transpositions at regular intervals, with each pair of wires swapped left-right to minimise cross-talk between circuits
Twisting wires is a common use case with certain applications like i2c, often it can be to stabilise the signal across the length of the cable.
With regard to most hobbyist electronics, it’s not an excessive issue unless you are working with high frequency where you may get some cross-talk or interference.
I can attest to keeping things tidy when putting my own projects together, there’s nothing quite like tidy wiring!
Lots of super helpful info here! I was most familiar with this from transmission/distribution lines as Bob and others mentioned. Twisting overhead cables decreases the negative effects of the natural line capacitance and inductance over long distances. You can read about it here:
You will also very frequently see high-power cables laid in what’s known as a trefoil configuration (basically just single phase cables in an equilateral triangle), the wires are often slowly twisted over the course of its run. This reduces the effects of self-inductance at high currents.
