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?
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?
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.
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
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?
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?
Hi,
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.
Regards,
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.
Regards,
...er, 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...)
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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...)
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westers151 said:
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.
Regards,
Pilli, another interesting idea and again something to think about.
Bob, I agree about the engineers not worying about the surface. Fortunately my engineer is pretty good about surface protection, however I'm sure he's not as good as I would be if I had the tools
My alluminium plate is going to be sprayed as I'm not a fan of brushed alluminium, but it will be sprayed using the "coat with P45 filler and sand smooth" technique that custom car shops use for getting their bodywork ready for paint. A lot of effort, but it pays off for a top class finish.
I'm actually wondering whether to bother with a switch, especially with your comments about their electrical performance and ability to handle inrush currents. I'm "only" building a chip amp, but the first one I built using a 300VA torroid blows any close coupled rated fuses at switch on, when it really shouldn't.
At the moment I'm using a 4A fuse with a light bulb connected before the switch to act as a soft start circuit, but I know I'm going to have to do some form of soft start circuit when I put my new amp into the casing, otherwise I'll not be able to use close coupled fuses. So the soft start circuit should reduce the impact of inrush currents and allow me just to use the mains plug as my switch.
Bob, I agree about the engineers not worying about the surface. Fortunately my engineer is pretty good about surface protection, however I'm sure he's not as good as I would be if I had the tools
My alluminium plate is going to be sprayed as I'm not a fan of brushed alluminium, but it will be sprayed using the "coat with P45 filler and sand smooth" technique that custom car shops use for getting their bodywork ready for paint. A lot of effort, but it pays off for a top class finish.
I'm actually wondering whether to bother with a switch, especially with your comments about their electrical performance and ability to handle inrush currents. I'm "only" building a chip amp, but the first one I built using a 300VA torroid blows any close coupled rated fuses at switch on, when it really shouldn't.
At the moment I'm using a 4A fuse with a light bulb connected before the switch to act as a soft start circuit, but I know I'm going to have to do some form of soft start circuit when I put my new amp into the casing, otherwise I'll not be able to use close coupled fuses. So the soft start circuit should reduce the impact of inrush currents and allow me just to use the mains plug as my switch.
Hi Westers,
Personally, unless you intend to leave the equipment powered up almost permanently, I would avoid using a mains plug as a switch, as, of course, they are not intended nor constructed for this application.
I have gone to great lengths in my domestic set-up where mains is concerned, with a dedicated system for my audio room, and all outputs are (unswitched) rhodium-plated MK outlets. I used to work in the jewellery trade and this was easy and quite cheap to do, and using switched sockets, even the same quality MK types, are sonically less good, unfortunately.
When plugging in an unswitched piece of equipment (i.e permanently 'on') which will draw current immediately any contact is made, you will quickly discover that the brass pins on the plug become eroded and blackened and this is not desirable in my view. In my case it would ruin the plug & socket's plating, of course, which I once did during a trial when I was developing and testing an unfinished amp design! Regrettably, using toroidal transformers does exacerbate the problem, and a 300VA toroid does have quite a high inrush current as you know. You wouldn't see quite the same problems with a similar sized "E-I" or "R-core" transformer as their inrush characteristics are less severe.
Even with a soft-start circuit, I would still be wary of using the suggested *plug* to make and break any contacts, if it was myself, and I would accept the slight deterioration attendant to using at least a switched mains outlet.
Anyway, I hope it works out well for you.
Regards,
Personally, unless you intend to leave the equipment powered up almost permanently, I would avoid using a mains plug as a switch, as, of course, they are not intended nor constructed for this application.
I have gone to great lengths in my domestic set-up where mains is concerned, with a dedicated system for my audio room, and all outputs are (unswitched) rhodium-plated MK outlets. I used to work in the jewellery trade and this was easy and quite cheap to do, and using switched sockets, even the same quality MK types, are sonically less good, unfortunately.
When plugging in an unswitched piece of equipment (i.e permanently 'on') which will draw current immediately any contact is made, you will quickly discover that the brass pins on the plug become eroded and blackened and this is not desirable in my view. In my case it would ruin the plug & socket's plating, of course, which I once did during a trial when I was developing and testing an unfinished amp design! Regrettably, using toroidal transformers does exacerbate the problem, and a 300VA toroid does have quite a high inrush current as you know. You wouldn't see quite the same problems with a similar sized "E-I" or "R-core" transformer as their inrush characteristics are less severe.
Even with a soft-start circuit, I would still be wary of using the suggested *plug* to make and break any contacts, if it was myself, and I would accept the slight deterioration attendant to using at least a switched mains outlet.
Anyway, I hope it works out well for you.
Regards,
Bob
Thanks for the reply.
Yes, I too wondered whether the plug would be suitable for being used as a switch and you've answered that question.
I think the easiest option is to install a switched IEC socket at the back of the amp. It's not pretty, but saves faffing about, plus it's out of sight so the ugliness will be hidden (and it can be easily reached in my simple setup).
I think my next project (a pre-amp) will have a front plate less than 8mm.
Thanks for the reply.
Yes, I too wondered whether the plug would be suitable for being used as a switch and you've answered that question.
I think the easiest option is to install a switched IEC socket at the back of the amp. It's not pretty, but saves faffing about, plus it's out of sight so the ugliness will be hidden (and it can be easily reached in my simple setup).
I think my next project (a pre-amp) will have a front plate less than 8mm.
Hi Westers,
I think that this is a very sensible move under the circumstances, and, longer term, I am sure you will not regret this slight additional effort.
Keeping all mains contacts very clean (some enthusiasts polish their mains plug pins with Brasso, to good effect!) is important in my experience, and UK brass plug pins will not take any switching abuse without detereoration and potential problems in due course.
Regards,
I think that this is a very sensible move under the circumstances, and, longer term, I am sure you will not regret this slight additional effort.
Keeping all mains contacts very clean (some enthusiasts polish their mains plug pins with Brasso, to good effect!) is important in my experience, and UK brass plug pins will not take any switching abuse without detereoration and potential problems in due course.
Regards,
I almost always use EMI filters these days, mostly to keep nasty things on the outside, outside. These modules (Corcom and similar) can be had with switches, plus the line voltage switching card and fuses, and can screw into any panel, unless it s a couple inches thick. Almost any power level is obtainable, though they might be a bit expensive. IMO, if you're doing 8mm thick chassis work, cost is of little concern
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