Star grounding and 9v

[Esppse]

Hello,

I have a project with nearly 20 circuits in it, I'm doing my best to star ground everything. Can I tie 2 circuit grounds together before they go to the star point, or should all go directly to that point?

Here's what I mean, is this ok?
https://hennulat.files.wordpress.com/2012/04/exampleofstargroundingmethodfrommtl2.png

With the 9V connections, do I have to star solder all the 9V points to 1 place, or could that be daisy chained?

[italianguy63]

You should try to "star" ground whenever possible.

You should avoid "daisy chaining" the grounds whenever possible.. it causes a "ground loop" and invites noise into your circuits.

MC

[anotherjim]

Yes, it may be the ideal to have everything to a single star point, but separating into sub-groups by function as above is more practical. It also makes sense for the power supply wires to have the same group paths.

[R.G.]

I have a project with nearly 20 circuits in it, I'm doing my best to star ground everything. Can I tie 2 circuit grounds together before they go to the star point, or should all go directly to that point?
[...]
With the 9V connections, do I have to star solder all the 9V points to 1 place, or could that be daisy chained?

What you are missing is that what matters is not the voltage of the circuit, nor the number of circuits, but the >current< in each wire.

Whether a power or ground net is OK or needs star grounding or not depends on what voltage drop the current causes in passing through the wire resistance, and how much that error voltage is amplified by the circuit. To do a proper job of designing a power or ground distribution net, you have to know the currents in each wire, both AC and DC.

The proper answer to your question is another question: what are the circuits, how much gain do they have, and what is the wire resistance?

That being said, for diy pedals, you can usually ignore the voltage drop in the power net, as very few pedals pull enough current to cause a significant power side voltage drop, and most circuits will have some degree of power supply noise rejection. Not all, but most. You can usually get away with daisy chaining the grounds, but not always. If one/some of the circuits pull significant current or are fed through long, tiny wires, it can cause a voltage offset on ground, which most circuits don't reject very well. If one/some of your circuits have very high gain (like headbanging distortions) then the ground offset can be amplified a lot.

There is a lot to learn about this, and you wanted a simple "yeah, it will be fine" answer. And that's close to the right answer, which is: yeah, it will probably work fine, but depending on the circuits and the wires, you may have to tinker with it, or go to star grounding.  You may have to work harder if your first lashup has problems. No way to tell at first. It can be shown that star grounding will always produce a lowest-noise result. However, it cannot be shown that something else won't work as well.

So try it, and star ground more as you need it. As a practical matter, clumping sections of circuit that handle roughly the same signal and same signal level can be tied together in a clump and the clumps star grounded. Running a separate wire to every part that connects to ground is a huge number of wires.

[Esppse]

OK thanks guys, they are 9v circuits, the wire bunch is already thick 11 wires in, I'll keep trying to do the 1 wire method straight to the star for the grounds. I would have liked thinner wire, I'm using the Tayda 24 awg, still not thin enough. Do you guys have recommendations for thin wire?

I bought 30awg by mistake, that was way too thin, but the jacket was thick, so that was a bad move both ways.

What is the thinnest jacket wire for about 26-28 awg stranded wire that's really flexible and won't rip? 30 awg rips off the solder point, very fragile.

[antonis]

I always use 0.5mm² (AWG20) for everything but indicator LED wiring...
(with 0.8mm diameter (0.032"), about 33mΩ/m wire resistance and more than enough strengh I feel I can sleep in peace of mind..)

I should also shake hands for AWG21 but nothing thinner than this..!! 

So, I'm not the most appropriate person for suggesting  evaluated cat whiskers..

[amptramp]

The #24 you are presently using is good for about 80 mA.  If you have 20 circuits you are feeding, you may be at that point already.  Telephone wiring is standard #22 or #24 gauge and there is a lot of it around.  If this is too thick, maybe you need to change the mechanical design to accommodate it.

[PRR]

> the wire bunch is already thick 11 wires in

You want a "ground bus". Google for pictures.

The usual ground buses are for #14 and above, won't grip your wee wires.

What I would do is mount two terminals 2 inches apart and run a bit of #14 wire between them. Hook your #24 ends and solder to this. For pedal-size signal/power currents, an inch of #14 is "nothing".

[Esppse]

Ah,

The ground bus i am using is a 1" x 0.5" tiny piece of aluminum. I severely underestimated my space requirements. The rest of this project will be like building a ship in a bottle I'm afraid.

I'm thinking about buying ethernet cables, and stripping them for their individual wires. They seem super thin and flexible. What do you guys think of that?

[PRR]

You can't solder to aluminum (not reliably enough for small electronics).

You need bigger. You need copper.

[thermionix]

I'm thinking about buying ethernet cables, and stripping them for their individual wires.

People tend to strip computer cables that they already have and aren't using.  I don't think it's very economical to buy a cable just to tear it apart.  If you have an old parallel printer cable, it will contain many wires with different color insulation.  They might be very thin though.

[Rob Strand]

You can't solder to aluminum (not reliably enough for small electronics).

We had some stuff at work that let you solder to Aluminium. 
Had to be seen to be believed.
Unfortunately I can't remember what it was called.

[Esppse]

Oh crap I didn't know about the aluminum, I'll replace with a different piece today. Yikes! I'll also scour for some cable to strip.

[highwater]

I'm thinking about buying ethernet cables, and stripping them for their individual wires.

People tend to strip computer cables that they already have and aren't using.  I don't think it's very economical to buy a cable just to tear it apart.  If you have an old parallel printer cable, it will contain many wires with different color insulation.  They might be very thin though.

+1

The innards of ethernet cables are great as jumper-wires for vero builds, but there's better wire for pretty-much everything else.

Solid-core, so it's sketchy for off-board wiring.
Thin-enough gauge to fit poorly in a breadboard, so even-though it'll work, you risk a bad connection.

Of course, the best kind of beer is free beer, so if you can get a leftover spool of CAT5 for cheap/free, go for it... but don't pay anything even *close* to full-price unless you're using it as network cable.

[Esppse]

Hmm, didn't realize cat5 ether net was solid core. I've only had bad experiences with solid core, always breaking.

Is this a good deal on bulk strippable wire?

https://www.showmecables.com/25-conductor-26-awg-stranded-pvc-cable-per-foot-1?gclid=CjwKCAiAiarfBRASEiwAw1tYvwadIdDvK8hefd5rl1YxluJ5JohJN6tDPZMjsei2pJeDnzW1SWfBzBoCvHYQAvD_BwE

Basically 4 cents a foot if you buy over 15 feet.

[PRR]

> We had some stuff at work that let you solder to Aluminium. 

I may have been draconian saying CAN'T. You can, but the magic potions and alloys are not on the pedal-builder's bench and expensive to buy. Cheaper to go over to your neighbor, the rich one with copper flashing on his roof, after midnight, with tin-snips, and score a piece of Copper. Or house-wire. There's other hardware like a big ring-lug, but unless you do mower repair it makes no sense to buy a 77-piece lug assortment for one job.

> cat5 ether net was solid core.

Net-cable exists both ways. Permanent install is solid. Jumper cables are stranded. You can buy the stranded stuff in 1,000' foot reels for making your own jumpers. At pedal-scale that is absurd. Better to cultivate the kinds of friends who use net-cables a lot. They (formerly me) will have odds and ends of cables. Just like guitarists today must have a box of misc 1/4" cables--- wrong length, not gaudy enough, or -quality. Since it is usually the ends that go bad, this is ideal fodder for salvage.

Agree that if an old printer (RS232, SCSI) cable or an old PC power supply was just as close, I'd like that wire better.

[Rob Strand]

I may have been draconian saying CAN'T. You can, but the magic potions and alloys are not on the pedal-builder's bench and expensive to buy. Cheaper to go over to your neighbor, the rich one with copper flashing on his roof, after midnight, with tin-snips, and score a piece of Copper. Or house-wire. There's other hardware like a big ring-lug, but unless you do mower repair it makes no sense to buy a 77-piece lug assortment for one job.

I agree 100% about not making things harder than they should be.    I was only mentioning that stuff or your interest.  It was actually easy to get not some hard to get industrial stuff.  The guy at work who found it made a sample to show people and it raised the eyebrows of a lot of well seasoned engineers.  The solder job was really nice.

[PRR]

I looked at some such stuff for a cracked guard on a vintage (hi-quality) circular saw. Yes, easy-click and they ship, and the price was not absurd for fixing an unobtanium part (but not much less than getting a new lo-quality saw). I suppose we should find it again because "somebody" here may need aluminum solder for a box or bracket. Of course the next issue is that the mini-iron won't ever heat a large lump of Aluminum-- I have the 450W iron but most here won't. Even plumber's torches are going out of style, since beginners can't seal lead-free solder and push-on plumbing connectors fill the store.

[Rob Strand]

I have the 450W iron but most here won't. Even plumber's torches are going out of style, since beginners can't seal lead-free solder and push-on plumbing connectors fill the store.

Those little butane gas burners come in handy.   Not sure if they will cope with a large aluminium plate.  (I saw a video of someone heating copper blocks in charcoal  .  Quite suitable for vintage mojo.).

[ElectricDruid]

The proper answer to your question is another question: what are the circuits, how much gain do they have, and what is the wire resistance?

With what R.G. said in mind, I'd say don't worry *too* much about the star grounding, and certainly don't start using thinner wires just to be able to tie everything back to a central point. You can get just as good a result in the majority of cases by running a nice fat copper ground wire around all of your circuits. It'll conduct multiple amps so easily than your puny effects circuits won't even know it's there. If you've got something really high gain and a bit sensitive, by all means, go ahead and give it its own ground wire instead. Like this you're only wiring up two or three ground wires, not a whole bunch.

My experience is that circuits that hum aren't humming because the ground wires aren't star grounded. There's usually something else going on (crazy gain, oscillations, no proper ground connection at all, bad ground loops, etc etc).

The principle is; if the wire resistance and the current are both very low (which they will be for a fat copper wire and a stompbox circuit unless it's frying chips) then any volt drops caused are tiny. So don't sweat it too much!