Auto dust collection when tool starts


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I have a new wet/dry vac that allows me to plug in my power tool and the vac will start when I power up the tool. Sweet.

I am now building a woodworking work bench with many of my power tools built into the bench (table saw, router, jigsaw, etc...). I want to have a power strip into which all of the power tools will be plugged in and I want to build my old shop vac (one without the auto start feature) into the work bench for centralize dust collection. I'm trying to figure out how to get it so that if I power up one of my built-in tools my shop vac will also start and then when I turn the tool off it, the shop vac will also turn off.

I guess the main problem for me is I'm not sure what this is called. Is it an automated switch or a trigger switch or what? Also I'm in Europe just to complicate things. I'm not averse to building the device myself if there isn't too much voodoo involved (like a raspberry pi).

Cheers,
 
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Your new vac must have some device in it that detects current flowing when power is taken by the plugged in power tool then presumably runs for a certain amount of time after the power tool is turned off - a bit like a bathroom fan with a timer. I have a large Bosch wet and dry vac that does the same thing. The current detector could be all manner of things but probably a PCB with maybe a current transformer, maybe a relay and a timer. I do a fair amount of electronics - voodoo - and could knock something up if I thought it worthwhile. It would end up as a box of tricks with the shop vac powered from it and one or more current sensors. The timer is easy and there are modues available to do that - sometimes described as run-on timers. The current sensor is trickier, but not impossible. Are you having individual nozzles at each tool? Axminster Power Tools used to do an extraction system but pricey. Maybe another approach might be to use a cheap radio controlled switch at each workstation. Europe shouldn't make a difference and Raspberry Pi would be overkill. However, my approach might be to use a microcontroller like an Arduino. There are chips that detect voltages - HCPL3760 comes to mind - but it could be over-complicated. Current sensors generally work on one of the phases or the neutral so you would need to access the wiring. The easiest way would be to make up a block to plug the tools in and get at the wiring in the block. Yes, it's doable, but...........
 
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Piglet has the right idea.
The current flow being detected is usually passed through a diode array. This consists of a chain of silicon diodes. One diode has a voltage drop of approx 0.6 volts, so if you needed 3 volts for detection, you would need a chain of 5 diodes. Back to back with these you put another set, connected in the opposite direction, so that the alternating current can flow in both directions. If you need a DC voltage for detection, then the back to back set could be just one diode conducting in the opposite direction. (The reason for using diodes, rather than resistors, is to be able to detect very small currents, yet pass much larger ones without a massive voltage drop and heat problem).
Of course you will need a circuit to detect the voltage, but I don't have any details of such.
The diodes should be rated to carry the maximum expected load current. It would also be wise to have their voltage rating at least 350 volts, since if one half of the 'back to back' set should fail 'open-circuit', the others will 'see' mains voltage across them.

The above describes Current detection, so only one sensing circuit will monitor each tool as it is powered up. It could be simpler to have a mains relay to detect Voltage on each tool, but this would have to be downstream of the switch(es) controlling power to the tools, with any further switches (eg on the tools themselves) left in the On position.
Or perhaps simply use double pole switches, the second pole powering up the vac!!

I hope this has helped.
 
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Another time waster. Two people help the original asker out and then silence. Blacklisted.
 

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