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710 posts

Ultimate Geek

#270665 21-May-2020 10:03
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I recently obtained one of those big 35L ToolPro vacuums from Supercheap Autos which I intend having semi permanently connected to a DeWalt job site saw.  The vacuum has a pass through power socket that senses when current is being drawn, and automatically turns on.  The problem is that the socket is rated at 1000W and the saw draws 2000W.  I rather stupidly thought I'd make a box with a power relay, but quickly realised that this wouldn't work as turning on the saw will not be seen by the relay's coil. 


I feel sure that it is doable, but I am not clever enough to work out how.  I thought about connecting the saw to the vacuum's pass through socket and have it power a relay which switched power in parallel to the vacuum socket, but it would need to split power between relay and vacuum socket or the vacuum would shut down. Would a power relay be fast enough or would the initial surge from the saw have time to damage the pass through circuit. 


I have a vague memory that thyristors are very fast and are available in that sort of current range, but I don't even know if they can handle main voltage, although it seems reasonably that they can.  If that worked it would need to unlatch to let the vacuum shut down.


I spent most of my working life designing and building test instrumentation at Ford Product Development in the UK, but I was mechanical although I did almost as much electronics because it was a small team.  That was a long time ago though, and I am out of my depth working out the above circuitry.  So any ideas would be welcome. It might be simpler to power the vacuum via the saw for instance, but I have only had the saw a few weeks and am reluctant to drill holes in the power box already.  Perhaps I could get an additional cable through the existing cable gland?


Incidentally, my standby solution is a power board with a remote ($29 on TradeMe).  

Trevor Dennis
Rapaura (near Blenheim)

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Uber Geek


  #2489093 22-May-2020 08:58
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I have one of these on the way to do my solder fume extractor via an arduino.


The power strips with the relay don't have a configurable delay for turning off. which you want to keep pulling till all the dust is out of the hose, otherwise it settles and may not move the next time the vacuum starts up. I have a problem with my soldering iron that the draw when its not heating is too low, and the powerstrip turns off, even when its set to the max sensitivity. Usually a problem when I turn the temperature down and it doesnt heat for a while


Also you will probably find the vacuum is 1400 watts since they only allow for 1000 to be drawn, so with the saw you are technically over the limit


600 posts

Ultimate Geek

  #2489101 22-May-2020 09:42
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I made one of these with a 16A relay built for this purpose. I'll find the details of it and let you know. Works like a charm! :)




Edit: Found it


Click to see full size



I'm not a complete idiot, I still have some parts missing.


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  #2489102 22-May-2020 09:44
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On the off chance you haven't considered it.

The saw and vac will need to be supplied from different outlets. The saw at 2000W and the vac at ?(>1000)W far exceeds the 10A rating of the plug. If this is a commercial premises, there is a chance the outlets will be on different phases, so be careful to not accidently get a 400V short circuit.

Location: Dunedin


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  #2489451 22-May-2020 13:35
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Also if you havent already considered it, one of these on a couple of tough buckets works great to minimize the amount in the vacuum itself.


dust cyclone on aliexpress




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  #2489456 22-May-2020 13:40
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one of these on a couple of tough buckets works great



Two buckets?  Interested to hear about the set up.


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  #2489491 22-May-2020 14:53
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YouTube must have at least 100 dust separator videos. It does add some resistance to the airflow. A jobsite saw will probably still spit dust out of gaps unless you can apply a lot of suck to the extract port.

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  #2489509 22-May-2020 15:35
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Two buckets?  Interested to hear about the set up.

One inside the other to resist it collapsing inwards due to the vacuum.


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