Plastic boxes

[rasco22862]

How do i make the holes for plastic boxes??, what are the right tools?   How do i secure the board and the battery to the box??

[sfr]

With a drill, just like anywhere else you want to make a hole.   Depending on the type of plastic used, you may have to be very careful about cracking the plastic - either step up the sizes of your drill bit and enlarge the hole slowly, or use a unibit.  Going with a large drill bit too early, and the thing often catch as it makes it's way out the back of the hole, often times cracking the plastic in the process. 

I prefer to start with a small drill bit and then grab my unibit to enlarge the hole, it seems to work fairly well.  Avoid using too high a speed (the plastic will melt, and the little shavings cut off by the drill bit will get stuck in the hole.  Let the bit do the work, don't push the drill, that will help avoid plastic cracking. 


I usually secure the battery to the box by screwing (or use an epoxy that will adhere to the metal of the battery clip) in one of those little 9v battery clips from Radio Shack, or by having the battery stuck between the sides of the stomp switch and the box's walls. 

There's a variety of ways to secure the board, I generally use board standoffs, or double sided foam tape.

With plastic boxes, you'll generally want to glue aluminum foil or some use some sort of metal tape one the inside of the box to make a conductive layer to shield things.  Make sure all of this layer has continuity amongst itself if you use more than one piece of foil/tape, (as you most likely will, at least for the box top/bottom!) and make sure it is connected to your circuits ground.  You'll also probably want to make sure all your jacks are grounded by wires rather than through the chassis as we often do with aluminum boxes.

-Joshua

[Mark Hammer]

If you plan on using plastic boxes a lot, it might be worth investing in a tapered reamer.  I've used plastic boxes quite a bit recently, and I can do pretty much all my "machining" by starting the hole with the tip of a utility knife and finishing up with a reamer.

Not all of us can work with drill presses, for either space, cost, noise control, or other reasons.  Reamers present a relatively quiet, neat (you can simply do it over a wastebasket), and inexpensive solution.  The only downside is the slightly longer time required, and the possibility of some repetitive strain irritation if you do too much in a short space of time.

[rasco22862]

Thank you very much to all. Does any have a photo of a plastic box with the aluminium foil already sticked??? I just want to see how its going to like like.

[Alex C]

Thank you very much to all. Does any have a photo of a plastic box with the aluminium foil already sticked??? I just want to see how its going to like like.

There is a picture in this thread of Basicaudio's Dr. Boogey in a wooden enclosure (scroll down a bit).  The same shelding principles apply.

[Mark Hammer]

I use copper shim that I buy sheets of from a scrap place near me.  You can cut it to shape/size with scissors, solder to it, and punch out the holes for pots and switches with a hand-held paper punch.

You can see an example of this in action here: http://hammer.ampage.org/files/Woody.zip   It's the picture labelled Woody2.jpb.  The shim material is held to the case by the parts fitting through it.  No adhesive.  Just be careful of the sharp edges!

[rasco22862]

But .. when the foil touch the potentiometer´s body..it act like a jumper between the 3 pins of the pot

[sfr]

The lugs on potentiometers are usually set back enough that they won't short out on the chassis - otherwise everyone of our builds in an aluminum box would have the same problem and be fraught with problems! 

Granted, using foil or something else you would need to be carefull that it was flush with the box so that this problem didn't present itself.  (I.e., you can't just throw a ball of foil in there and hope for the best) but you should be fine. 

The body of the pot will connect to ground, but the lugs of the pot are electrically isolated from the body of the pot.  (Although if you need to send one of the lugs of the pot to ground, like in a volume control, the back of the pot become an easy place to make that connection - although not the best because then your ground connection is dependent on the pot staying securely fastened to the ground plane of the chassis.)

[choklitlove]

you don't absolutely have to shield.  it's a good idea, but i don't.  however, if i found some bad humming or noise after i'm done, i would definitely go back and sheild it.  also, there is a spray-on sheilding option as well, but i have never tried it.  other than that, the rest of the process is identical to metal boxes for me.  i drill with standard drill bits, starting small and moving up to the desired size one bit at a time.  i use hot glue do secure the battery clip and the board. 

good luck, and don't use so many smilies!

[Paul Perry (Frostwave)]

On the subject of plastic boxes, never be tempted to use your soldering iron to make a "starter dimple" when you are drilling a hole in the box.
Because, it can screw up your tip big time. I don't know the chemistry behind it - I suspect chlorine is involved if the plastic contains it.

[Mark Hammer]

But .. when the foil touch the potentiometer´s body..it act like a jumper between the 3 pins of the pot

It's nothing that a small piece of electrical tape sitting under the pot can't cure.  Personally, I try to use some heatshrink on my pot lugs these days as strain relief for the wires when twisting things around to insert them into the holes or position the board just right.  Not only does it keep the wires from fracturing, but it also keeps the pot lugs from shorting out against anything near them, be it chassis, shielding, the body of the pot next to them, the tips of vertically mounted resistors, etc.

If it was a pedal that I had built 100 times and knew where everything went, I wouldn't see the need for it.  The problem, and ned for strain relief, arises when it's a first build and you're sort of winging it without any foreknowledge about necessary lead lengths, etc.

[Rafa]

I use wooden boxes, cheap, easy and you can build the size you want.
For plastic boxes I would use a drill
Cheers
Rafa

[brett]

Hi
I'm putting a 6W amp in a little plastic box.
First, I'm using shielded wire, to avoid most interference, then doing basic shielding with two flat pieces of tin in the top and bottom of the box.
Not perfect, but easy to do.
cheers

[rasco22862]

can i paste the aluminium foil to the box with stick glue, glue,, clear tape?? Wich one??
Thanks to all for your replies

[rockgardenlove]

You might consider buying a role of that sticky backed copper shielding tape.

The conductive paint works well too.

[rasco22862]

can i paste the aluminium foil to the box with stick glue, glue,, clear tape?? Wich one??
Thanks to all for your replies

[Seljer]

yep, aluminum foil and glue works fine for sheilding enclosures (and guitars too)