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Real basic beginners question here.  How do you mount things like PCB's and other components in an electronics project box like this?: -



I see a lot of components have these circular holes in the corners, like on this relay: -



So how do you mount it?  In the case of the relay it's obviously high voltage and I'm guessing drilling holes in the box and mounting it with screws isn't correct.  So what is?

Thanks and forgive me for asking something so basic.

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Typically, you use standoffs.   If you need insulation, you can get nylon standoffs & nylon nuts & bolts.  (Of course, you have to drill holes in the box.)

I've heard about people cutting-up a BIC pen to make a standoff, and running a small machine bold all they way through.

Or if it's a plastic box, you can usually just bolt the board to the bottom of the box, as long as you don't tighten the screws too tight and bend the board.  Then if you are worried about the screws comming loose, you can use some loctite or hot glue.

A couple of times, I've used some Foam Insulation Tape and super glue as a quick-and-dirty solution... But I'm not recommending that.
« Last Edit: May 20, 2013, 02:51:29 pm by DVDdoug » Logged

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One tip is to mount things on the lid and turn the box upside down. This allows you a lot of room to work while it is mounted.
There are lots of ways, standoff or pillars have been mentioned, I use brass tapped hex ones. Also angle aluminium can be used to bolt the cards to vertically.
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One tip is to mount things on the lid and turn the box upside down. This allows you a lot of room to work while it is mounted.

This is how I generally build things too. Rotary encoders, push buttons, LEDs etc. can be mounted directly on the circuit board, with holes drilled in the lid for them to poke through. This reduces the number of wires I need coming off the board. If I can't get everything on one board, I use 2 boards stacked one above the other. I generally use nylon M3 standoffs for my own boards, but I find M2.5 ones fit LCDs better.
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Yes it is not always easy to get M2.5 screws most suppliers consider M3 as very small.

If you take a look at the projects here:-
http://www.thebox.myzen.co.uk/Hardware/Projects.html
You will see a variety of techniques.
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Hot Air glue gun to temporary fix it.
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Real basic beginners question here.  How do you mount things like PCB's and other components in an electronics project box like this?: -

a) The big piece of plastic is the lid. The thin one is the base.

b) Drill holes in the base and use standoffs.

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Rather than drilling holes, another solution you can try is:

1) Attach the standoffs to the board you want to mount.

2) Apply epoxy, super-glue, or some other similar multi-purpose/multi-material high-strength adhesive to the ends of the standoffs.

3) Position and apply the standoffs onto the surface your want to attach to.

Once the glue sets, you can then unscrew the board from the standoffs, and they will remain in place. Be careful not to get any glue onto the board or the screws holding it to the standoffs, of course.
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2) Apply epoxy, super-glue, or some other similar multi-purpose/multi-material high-strength adhesive to the ends of the standoffs.

That's a nice solution if the box you are using is made of something that you can get the glue to bond with, but I'm not at all sure it will work with ABS, which is what most plastic enclosures are made from. Do you know of a glue that works with ABS?
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...but I'm not at all sure it will work with ABS...

I am certain.  Normal epoxy does not bond to ABS.

With an interesting exception: openings in the ABS give the epoxy a "bonding" point.  I have had success "gluing" tactile pushbuttons into openings.  The epoxy forms around the opening edges holding the pushbutton in place.
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Epoxy works best in my experience, I used to have 1 in 10 separate from the panel until I began roughing up the plastic and fixing a small washer (I like outside star lock washers) and a grey epoxy resin used for automotive repairs called JB Weld. The curing time can be accelerated by heating to 45 deg C or 115 F for 30 minutes.
This was a technique that I used to make field testable models that let me finalize circuit board sizes, mounting holes and cutouts required for a final drawing, PCB layouts (mounting holes) and battery holders for SLA batteries in both plastic and aluminum.

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I am certain.  Normal epoxy does not bond to ABS.

Hit it with some coarse sandpaper first and it should stick well enough for this sort of thing.

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In the crafting circles, I often times see a recommendation for the site: http://www.thistothat.com/ as a reference of what type of glue to join two different things.

For plastics, it looks like their first choice is 'Household Goop' (http://www.thistothat.com/glue/hgoop.shtml), with the note that Goop is formulated differently in different parts of the world due to local regulations.  The Canadian goop for instance contains perchloroethylene which is a known carcinogenic.  The U.S. Goop formula contains toluene, which although is a dangerous solvent, it is not carcinogenic.  However, toluene is much more flammable than perchloroethylene, so it is a matter of pick what you want to safeguard against (which in turn sounds like a discussion of lead-free vs. lead containing solder).

On some plastics, you want to use sand paper to rough it up, and with most glues, you want to clamp it in place for 24 hours or so.
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Many consumer products use 'hot glue' to hold circuit boards, components and small wiring harnesses in place. I've had limited success with it, it tends to break loose under extreme cold, vibration and sudden shock.
I've had similar results.  In addition, if you live in a hot place, the glue might melt without the iron.

Also, some cases have internal mounting boards that are available, such as this case that I've thought about: http://www.polycase.com/wc-23#.  In terms of the Arduino, my Uno has 4 mounting holes, but the hole next to the reset button is too close to the pin's to be able to use a screw to attach to the stand-off.
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...but I'm not at all sure it will work with ABS...

I am certain.  Normal epoxy does not bond to ABS.

Well - when I think of epoxy - I think JB Weld. That said, I have the cover of an old battery from a Motorola "brick" phone that I use occasionally for mixing epoxy; I can bend it and pop the epoxy off (mostly). Not sure if it was made of ABS or not...?

With an interesting exception: openings in the ABS give the epoxy a "bonding" point.  I have had success "gluing" tactile pushbuttons into openings.  The epoxy forms around the opening edges holding the pushbutton in place.

One thing I had done to get some of the epoxy off that battery cover was to use a hammer and chisel it off; but I found the epoxy would stick better the next time around (perhaps the gouges were making it easier to "stick"). So you could probably just sandpaper it some to make it stick. Worth trying out, at least.

I've found JB Weld to be good for sticking together just about anything; my "worst" application was on an anti-backfire valve on my 79 Bronco. That valve is virtually impossible to find, and the one that I did find (off a junker engine) was broken. I JB Weld'ed that thing up, and it's been on that exhaust header for several years now, without failing.

I've also seen JB Weld hold together a blower on a diesel engine, on my brother-in-law's old Ford dump truck; the blower cover was an aluminium casting, and had cracked. My brother-in-law had no way to weld the aluminium, so he JB Weld'ed the crack. It held for over a decade, then the blower failed again. That's when I first saw it. It had cracked in a -different- spot; he told me about using JB Weld on it the first time, and showed me the repair he had made before; it was still holding fine. Of course, after the second crack occurred, he decided to get a replacement blower.

All anecdotes, of course - and says nothing about ABS.

Gorilla Glue (or another polyurethane-based glue) might be another possibility. Something else to try might be to get some ABS solvent (ABS pipe "glue") and take a little bit of it and mix in some ABS shavings to make a "plastic blob", then embed the standoff into the blob onto the ABS piece you are working with (probably a metal hex standoff would work best - basically, the idea would be the inside threaded end of the standoff would secure it longitudinally, while the hex part being embedded would keep it from rotating - but that's all just a guess).
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