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westers151 10th March 2009 12:18 PM

How many people implement switches?
When building your own equipment casing, how many bother with switches and how many just unplug the device from the mains (or if in the UK, use the mains switch)?

Reason I ask is I'm building a case with 8mm thick front and back plates and trying to find a switch to fit those is so far proving impossible. I'm just thinking of putting in an IEC socket at the back which can be screwed in (not clipped in, again impossible to find for 8mm thick casing), but all the screw in IEC sockets come without a switch.

Do we really need switches if unpluging from the wall is used instead?

HK26147 10th March 2009 12:29 PM

For PA equipment and commercial installs, a power distribution strip - a "distro" is used for flexibility.
On a home level, I go from an isolated ground circuit to a small distribution strip.

Steerpike 10th March 2009 12:45 PM

It seems strange that you can't find any switch to fit a panel that thick - or do you need a very specific style of switch?

westers151 10th March 2009 01:34 PM

I've actually now found a switched IEC socket that can fit to 8mm thick material via screws, but yes it is strange to not be able to find switches for that kind of thickness material.

To start with I was looking for a nice round metal push button switch, but because of the current required ( 3 Amps or more) it very quickly narrowed what was available. Then add to that double throw latching requirement and it reduced it even further, and finally wanting one to fit 8mm thick material reduced it down to zero.

So I expanded my searches, but even for rocker swictches the thickness of the panel is too great - most are designed to fit about 3-4mm thickness.

So now I have to re-design my amp to either have a switch at the back, or just an IEC socket and no switch apart from unplugging it from the mains.

I tend to unpluf my equipment when not in use, so I'm not sure if I'll bother with a switch.

john blackburn 10th March 2009 02:35 PM


If you are wanting to use one of the round vandal proof switches take a look at this page About 2/3rds of the way down "doing it discretely"

Or a more complex variant

I haven't built either circuit (yet) but I like the look of the vandal switches also.

Hope it helps.


westers151 10th March 2009 05:12 PM


Thanks for the links and yes I was looking at the vandal proof switches. Farnell have one that will fit an 8mm panel, but my problem was that it's a momentary switch. However that discrete design looks like an answer.

Some questions:

It looks like this isn't a mains voltage switch as it appears to be powered by DC current (load + and Load - ). So this would come after the bridge meaning that it stops current from transfering through to any components when in the off position. However the transformer would still be live and drawinf current, unless I also unplugged the mains cable from the wall. So I'm guessing that the discrete version is more akin to a standby switch?

I also assume the 12V line is just to show that the input load is reduced down to 12V by using the Resistor values shown?

Bobken 10th March 2009 06:46 PM


One way of overcoming too-thick panels like this and still being able to use almost any choice of switch is to mount the switch on a thinner sub-panel. So long as a cut-out (one is needed anyway for any switch mounting) is made adequately-shaped and large enough for free access and actuation of the rocker, or whatever, then this sub-panel can be fixed from within the inside of the enclosure.

Often a 'recessed' switch like this can look very attractive on a front panel and it is less prone to knocks or accidental switching. It can look quite 'professional', and I usually chamfer the edges of the larger cut-out/recess with a 45 degree angle for aesthetics

I have done this several times sometimes using a s/s inner panel, and sometimes aluminium, mostly drilling and tapping the fascia from inside and fixing the thinner panel with some threaded screws, but on occasions I have epoxied the sub-panel in place when machining for screws has proved difficult.

If you have access to good machining facilities, another method is to 'relieve' the panel's thickness with a milling tool from within (or if it is done carefullly with a nice 45 degree chamfer, possibly from the outside) over an appropriate area, and once again a more conventional choice of switches can be used.


westers151 10th March 2009 08:17 PM

That's an interesting idea Bob and I hadn't thought of that. I know of an engineer local to me who can do the machining.

I'll have to do some more thinking on it.

pilli 10th March 2009 08:54 PM, why not just an extension shaft that goes through the front panel and operates the switch "somewhere else"?
This way you have the physical switch close to the place where the plug is (back panel) and you operate it from the front.

(Edit: to answer your question: me, always a double-pole switch, even in prototypes with no case -- especially in prototypes, actually: on-off too often while testing...)


Bobken 10th March 2009 11:02 PM


Originally posted by westers151
That's an interesting idea Bob and I hadn't thought of that. I know of an engineer local to me who can do the machining.

I'll have to do some more thinking on it.

I am fortunate in having my own machining facilities to do this work, but I am sure that any local engineering shop would be able to do this for you.
Just watch that the guys don't damage the panel when clamping it for any machining work, as they don't usually need to care much about the appearance of engineering-work they normally undertake. Assuming that the inside is relieved, the surface finish of the routed area after using an end mill is unimportant in this instance, luckily.

For me, this approach is imperative, as I am particularly fussy over the switches I use from their electrical performance aspects, and their aesthetic appearance. High-inrush switches for larger projects are not so plentiful, and none that I am aware of will fit in a panel of your chosen thickness.


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