Best Practice - Eeschema schematic for PTHs

I was going to strain relieve them. Thought about doing a little routed notch instead of a hole to give a spot for some silastic.

If cost is not a big factor then I second Reneā€™s suggestion of using screw terminals. Another perhaps sexier option is to pick a widely-used connector like JST XH 2.5mm or PH 2mm and buy pre-crimped cables from Amazon, RC hobbyist sites, or AliExpress. Put a male header on your board (footprints exist in the standard libs, and Digi-Key sells the parts) and buy cable assemblies with a female at one end and stripped/tinned ends at the other, which you will solder to your jacks, batteries, footswitches and whatnot. Soldering wires to the PCB is bush league and always ends up causing some kind of inconvenience at best.

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You are absolutely right. Should be something like this.

Thatā€™s kind of overkill - screw terminal and plug-in connector. I was thinking board-mount terminal block or JST header.

One thing that I see in that picture that isnā€™t overkill for screw terminals: ferrules. For stranded wire, crimping on ferrules before inserting into screw terminals will save you tons of headaches keeping individual wire strands under control.

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Yes, but not really. Depends on the job. This board is meant to be a pro safe, quick, no fuss connect setup.

For the application at hand in here, a simple soldered-in screw terminal would do.

However there are still those screw-forces against the PCB. A downside with soldered in screw terminals is that they tend to twist quite a bit. Too much force and the PCB goes as well, just as in direct soldering to a PCB.

Cheers

Thatā€™s exactly why I put them there. :wink:

This is what Iā€™m talking about. Youā€™d have to be quite a brute to rip apart a PCB with a 2mm screwdriver blade in one of these.

https://www.mouser.com/ProductDetail/Phoenix-Contact/1725656?qs=sGAEpiMZZMvZTcaMAxB2AF3qQv3QF5c1ecFGX7dSNmE%3D

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Iā€™m quite clear on what you mean. Still those green connecters are mostly somewhat softish which turns them quite easily. Perhaps the soft ones are the usual cn copies.

If it would have to be a PCB screw terminal Iā€™d rather go for the more solid versions.
Like those terminal blocks etc.

Those greenies might be suitable for ā€˜low endā€™ applications, however, experience shows, in professional environments people just go for it and expect connectors take just about any abusive treatment.

Cheers

There are reasonably priced crimping tools out there (modified general purpose crimp tools).
They are not perfect but good enough. And JST connectors are also quite easy (and reasonably cheap) to get from RS, digikey, ā€¦ (Farnell if you need a larger number of them.)


Looks like phoenix MSTB series. Might indeed be overkill. (They can carry 13 to 16 amps depending on which exact type. And up to 630V depending on environment conditions.)
The MC series might be an alternative (8 amps at 250V)
Both are available in higher voltage ratings (MC up to 400V, GMSTB increases the rating for the MSTB series, but only for harsh environments.)


A typical terminal block should at least be comparable to the MC series. (If you buy from a well known manufacturer. Cheap no brand types are hit and miss affairs.)

JST XH can carry up to 3 amps at 250V. PH a bit less. (Benefit of XH is that it comes in 2.5mm pitch which is compatible to strip boards for surprisingly high pincounts.) Another alternative to XH is the EH series. (Has the same pin pitch but takes up less room.)

I agree that screw terminals are probably the most reliable way to connect, especially for power connections. But in addition to budget, they eat acreage, and vertical clearance. And for signal connections (not power!) factors such as shielding and controlled impedance come into play.

With some things, you can differentiate between high-performance, and mediocre-pretender, from half way across the room. I canā€™t say that about screw terminal blocks. To my eyes the cheap ones look identical to the good ones, but I have seen the cheap ones break apart when you tighten the screws. (OK, the guy turning the screwdriver was sometimes known as ā€œRatchet Wristā€ but, like @JuliaTruchsess said, the torque you can transfer through a small screwdriver is limited.)

Dale

P.S. - Does anybody here know the idiom, ā€œseven levelā€?

That would not be my main worry to be honest. How the terminal block behaves when you give it its ā€œratedā€ current is another thing. I have seen these cheap ones melt. (And heard about some beginning to burn. If you want to see this check out a 3d printing forum as some of the self made electronics used the cheap terminal blocks near their documented rating -> too much if you are at these currents for hours on end.)

The ones made from proper material can loose all their metal parts to heat damage but still have the plastic intact enough not to make o bad situation much much worse. They will not start to burn or give off toxic fumes. (Well there is a reason why a phoenix made screw terminal costs an order of magnitude more than a cheap knockoff. Possibly more difference if you order in low quantities.)

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Yes, you are very correct! Thanks for the reminder - for the last two decades or more I have not been around circuitry capable of more than a few amps. (Neglecting, of course, the co-worker who put a couple of AA alkaline batteries in his pocket along with coins, keys, and loose hardware, and received an uncomfortable burn in a rather personal place as a consequence.)

I vaguely recall an incident from many incarnations ago (circa 1981?). This involved full-size ā€œbarrier blockā€ screw terminals inside a piece of equipment that had suffered a serious malfunction. Like you said, even though the terminal block was grossly distorted and malformed from overheating, it managed to keep the wires from coming completely loose or shorting against each other.

Dale

Sure, and I have those, but crimping is a time-consuming and not-fun task that is non-trivial to do properly and easy to do wrong in a failure-prone way. Personally I find it more efficient to just buy cable assemblies from people who specialize in making them and who have professional production tools. For the cost of one decent hobbyist-level crimping tool I can buy 100 assemblies.

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That is an efficient approach when you have simple interconnections. Cost explodes exponentially when you have, say, a harness assembly with 3 or 4 connectors, requirements for insulation color-coding, etc. ā€œIWISSā€ makes a variety of manual crimping tools that effectively deal with a wide range of terminal types (e.g., IWISS Sn-28B happens to be sitting on my desk at the moment because I recently built a harness using Molex power connectors).

And then there is the problem of justifying even US$25 for a crimping tool, when the prevailing mentality is to ā€œcrimpā€ terminals and contacts with needle-nose pliers!

Dale

The OP said heā€™s building a guitar effects pedal, and Iā€™m assuming (perhaps wrongly) that the cabling is not too fancy.

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OK, thanks for dragging me back to reality! :blush:

On the other hand . . . . Iā€™ve seen a few items that had been used on stage, and a full ruggedized, MIL-Spec, shake-table, drop-test may not be inappropriate.

Dale

oh horror :-1:

Those ā€˜connectionsā€™ never last, are always shaky, and the wires are easy to pull out by hand. Flag that.

For reliable connections there is just no way around professional crimp tools. Just the way it is.

Cheers

Specifically an SMD pedal design to be assembled by a group of musician friends that want to learn a bit, and feel like theyā€™ve made something. The project got derailed by family medical issues, but Iā€™m now back to do the layout.

Iā€™m leaning towards JST headers with bare leads coming out to solder to the pots. Folks can then just solder the headers to the PCB, and then solder to the pot lugs.

For a THT plated through hole or SMT pad where a wire is soldered, for the graphic symbol I use a connection dot, which is a filled circle. [See IEEE 315, clause 3.1.6 Junction of paths or conductors, clause 3.1.6.1 Junction (if desired), and clause 3.1.6.2 Application: junction of paths, conductors, or cablesā€¦] The class letter I use is WT [See IEEE 315, clause 22.4 for class letter ā€œWTā€ and the note that states ā€œNot a class letter, but commonly used to designate a tiepoint on connection diagramsā€.] I figure that this is a tiepoint between a wire and the trace on a PCB.
ā€“Regards, Larry

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