Tony,

Having read my own post, I came up with the same idea:  :-)

On Mon, 25 Sep 2006 22:27:55 +1000, Tony Smith wrote:

> You can buy magnetic switches.  This idea is you can only turn them on when
> power is available.  If you have a blackout, the device doesn't restart when
> the power comes back on.  Quite handy for things such as tables saws and
> drill presses.  They're a bit pricey, so you might just have one to feed all
> of the sharp/hot/spinning things.

They are available as accessories for machine tools (even router tables, which may be the cheapest way to buy them).  They're called "No-Volt 
Release" (NVR) switches here.  Probably a good idea to divide the mains supply into three:

 - Things which mustn't come on after a power cut (anything that moves or gets hot) fed by a NVR switch
 - Things that you want to carry on working for some time into a power cut (computers, communications, some lights) fed by a UPS
 - Things where it doesn't matter if they can come and go with the power (test equipment, room heaters, AirCon) fed from ordinary mains

The first may have a subset which is those things that you want to have an Emergency Power Off function, like PSUs for running experiments and 
projects 

>... 
> > Some jobs that need close visual inspection but don't take 
> > long (say drilling PCBs) may be better done standing up, so a 
> > higher-level work area would be useful.  Your central vacuum 
> > should have a port there, to extract drill waste.  It could 
> > also be used to hold down PCBs being drilled, by having holes 
> > through the table.  Did you know that MDF is porous, and 
> > small pieces can be used as a sacrificial support and will 
> > "transmit" the vacuum to hold the PCB while you drill?  Paint 
> > or varnish the parts (edges at least) where you don't want 
> > the vacuum to act.
> 
> And put the compressor outside!  Damn noisy things.  You can use a
> compressor as a vacuum pump, just hook it up to the inlet side, most have a
> threaded hole for this, with no connector fitted.

You can use this for vacuum hold-down, but don't use this as the vacuum system for removing drill debris!  You need a collection bin and proper 
filtration for that, and compressors aren't expecting to find debris coming into their inlet.  You can use an ordinary vacuum cleaner for this, maybe 
with a pre-collector/filter or a workshop dust extractor.  Either way you need to make sure that there is a reasonable airflow through the system, 
since a lot of workshop extractors and all domestic vacuum cleaners that I'm aware of use the airflow to cool the motor.

Cheers,


Howard Winter
St.Albans, England


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