fixing board to enclosure

[scaesic]

how do people fit their circuits to the inside of a metal enclosure?

[C Bradley]

Most people use stand-offs; something to keep the board from touching the metal enclosure and causing an electrical short. Standoffs can be bolted to the enclosure or glued. I've tried using super glue, but it eventually comes off of metal. I've heard that people get good results using epoxy to attach their stand-offs to the inside of their enclosures.

You can buy stand-offs or make your own. I make my own out of 3/8" wooden dowels.

[scaesic]

where about may one buy standoffs in the uk?

[nelson]

www.rshelectronics.co.uk


www.maplin.co.uk

www.cricklewoodelectronics.co.uk


www.farnell.co.uk


www.rapidelectronics.co.uk


www.londonelectronics.co.uk



etc etc etc

[audioguy]

I use some nylon screws with a nice falt head.
I check for placement, use some Dow 838 to 'glue' the scew to the box. I then drill the appropriate sized hole into the board, fit the board onto the scew and then put the nut on to eliminate the possibility of shifting.
You could probably use the same method with a plastic sheetrock wall anchor.

Have fun
Audioguy

[Threefish]

I've secured a couple of boards inside enclosures by using a PCB-mount socket for the input or output ,  so the board is hanging off the socket. I've only done it with small circuits (Fetzer valve, thing modulator), so the weight hanging on the socket/board solder joints and the socket itself isn't much. You probably couldn't really do this with larger circuits, though you could use the idea with both the input and output sockets being PCB mounts, so the board's located at two points, but could be tricky getting it in.
I'm sure I've seen others do this - is there a reason why I shouldn't do this (please tell me), but it works ok for me.

[petemoore]

I just take me a hard piece of clear packaging plastic insulation like the soldering iron or other stuff comes in, cut to size and with one hole poked in it, I through screw the box [drill a hole] and the insulation, then thread the screw right into a perfboard, and tighten only enough, too much might bend the wires on the pad side.
 Fast install, super fast de/re-installs, no chance of shorting to box if Insulation piece is sized right, all the materials are just there.
 This perf has proven to accomodate self threading screws very well.
 Doesn't look super pro but works like it.
 Bigger boards I hook on something for the one side, like a pot or whatever, or use two screws.
  Smaller boards, with one screw, don't seem to wiggle at all.
 This method also puts the ground plane as close to [but not touching] the underside of the board as is possible.

[gaussmarkov]

i have seen some people use plastic pcb mounting hardware, like mouser part no. 561-LAD187.  someone also mentioned once on this forum using double-sided sticky foam pads.

i really like petemoore's idea.  one advantage he didn't mention is that it takes very little space.  i am trying to fit a circuit with 4 jacks into a 1590b clone.  standoffs will take up too much room.

petemoore, it sounds like you think having the ground plane close to the underside of the board is a good thing.  is that right?  i'd love to know why.

[petemoore]

Ground plane is most effective [if it does anything] when run close to the board. Nothing happens at ground, if the box is grounded it makes a ground plane.
 Commercial effects very often use this method [look at Boss Dan-'s etc] to eliminate [don't quote word here] heterodyning...
 Basically it 'damps' down cross circuit 'chatter' from being introduced to the signal path as easily, since it 'absorbs' [again Dont Q me on this] flying electrons that would otherwise be more likely to 'impact' the SP.
 Shielded wires are basically 'circular' ground planes, encompassing the SP in ground.
 Amps and power supplies are sometimes isolated with a ground plane in the form of a sheet of conductive metal in an L shape, or three sided box, this either deflects electromagnetic activity or absorbs it.
 Hopefully some kind 'AEE' type will find my questions in there and straighten us out on this  :oops: .
 Basically it puts a layer of 'shielding' right next to where the SP and PS activities are.
 This method also makes for wires 'tied down' when they come from the board, [I make the wires come from the Bottom of the board FTMP], so they too can easily be shaped and 'placed' by the ground plane of the shielded box.
 I use the 'extruded edge' of say a plastic resistor package [where it's 'doubled up and the top and bottom halves meet], drill a hole in the edge of the board, the raised plastic section fits outside the screw on the edge of the board, so it pulls the other side down first, threading the screw in at a slight angle also helps pull the far side of the board down.
 My RACO's have two knob or three knob layouts [for the most part], and a little hole for the board mount screw in the side near the bottom[just a reamed out, pre-existing junction box to junction box bolt hole] or in the top near a side, [after side box or boxtop circuit placement, this is where the edge of board would be] I can change a box's circuit pretty easily.
 Sometimes I find or can plan a layout that leaves a padhole right in the midle of the board for screwing the board down, as long as the screw doesn't touch any wires.
 Anyway, with this method, I can see what I've got and where I want to put it, then have it done PD Quick. The plastic holds the screw [if you screw it back in a bit  :wink: ] while the board is out, I haven't lost or dropped a board mounting device in a long time, and have plenty of free spares I got from ol VCR's.

[gaussmarkov]

thanks!  i had noticed that boss pedals insulate with a single piece of clear plastic and was contemplating that approach.  but they don't need to fix their board to the box because it's kept in its own compartment.  your idea seals it for me.  i'd like to countersink the screw head so that it doesn't stick out of the bottom.  is that what you do?

[Paul Perry (Frostwave)]

I've secured a couple of boards inside enclosures by using a PCB-mount socket for the input or output ,  so the board is hanging off the socket. ... You probably couldn't really do this with larger circuits, though you could use the idea with both the input and output sockets being PCB mounts, so the board's located at two points, but could be tricky getting it in....
I'm sure I've seen others do this - is there a reason why I shouldn't do this (please tell me), but it works ok for me.

If you have a board that is held to the back of the case by jacks, and to the front of the case by PCB mounted pots, it could be (depending on geometry and order of tightening nuts) that you put strain on the board or mounted components, even to the extent of cracking something. So watch for that.

For my commercial boards, I have a small board that mounts via 4 or so PCB mount 1/4 hacks, and the main board that mounts via 5 or 6 PCB mounted pots, never had a problem, ever.

Previously I used those plastic adhesive standoffs, never had a problem there either. Even after a decade!

[petemoore]

K judge the boards as stiff enough to be held in place by one point...hadn't researched it except to mount most all of them this way.
 Using the 'edge' screw with the plastic causing the far end [non screwed down side] of the board to be pushed down...I noticed no flex at all on the non holed border.
 At some point I learned to 'trust the wedge', tightening enough for security but less than overtight. It doesn't take much to pin the board down...I've kind of made an art of it...  
 I'm just careful to set the screw exactly where I want it and no more, as long as you're careful with this part, and the insulation is complete, I don't see much risk of the stress being any much higher than that of the 4 screw into 'pylon' method, which looks alot more professional and is the standard, time tested method of board securement.
 I like the access to B.o.Board, the screw that doesn't come off, the ground plane and the ease of mounting. As far as the structural damage control, I'm pretty certain I haven't structurally stressed anything near to damage levels...it's been a while, time will tell.

[Connoisseur of Distortion]

my board is held in place by wire. i use 16 gauge solid core wire, however, so it doesn't really matter what i do in terms of standoffs... the wire will win. i usually position the wire so that the bottom of the board is visible when you open it, and so that the circuitry comes to rest against the bottom of the box when applied. then, a simple layer of electrical tape will do the trick.  

[petemoore]

my board is held in place by wire. i use 16 gauge solid core wire, however, so it doesn't really matter what i do in terms of standoffs... the wire will win. i usually position the wire so that the bottom of the board is visible when you open it, and so that the circuitry comes to rest against the bottom of the box when applied. then, a simple layer of electrical tape will do the trick.  

Well this too sounds to me like an excellent method. I'd have to rethink all the details...pretty good...seems like you could 'bridge the board right over pots !?

[Melanhead]

I used RG's suggestion of Velcro ... Works great as long as you don't plan on tweaking it every other day

I've also just put foam around the board and some tape to keep it on ... board floats freely but doesn't move much.

[petemoore]

The Main thing I notice with 'bad' mount or no mount is if something touches that shouldn't.
 In the long run using connection wires to do the 'mounting', if it's stiff enough will hold the board, reflexing of one point in a mount/connection wire could lead to problems down the road.
 If the board is secure and the circuit works... . If pro level mounting is desired use a Tried and True method.
 Tried and True for my boxes is too extreme, I like to weigh the odds and take my own chances, 'cause I'm an 'ol corner cutter.