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by Andy DJ

Auto-On Shop Vac Controller

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This controller switches on an attached vacuum when a power tool is in use. It's made with many found or "spare" components I already had on hand.

Auto-on shop vacuum controller module showing attached 4-gang extension strip, single mains socket for powering the vacuum, and mains plug to provide power to the whole lot.

Problem statement

When I switch on a dust-making tool like a router or mitre saw, I want the vacuum-cleaner attached to the dust extraction port to come on automatically. It would be great if it stayed on for a while too, so that it clears the hose of lingering dust. I also want to be able to attach several tools to the controller so that I don't have to keep unplugging and replugging the mains leads. The vacuum hose can be reattached easily enough, however. I have developed a simple, resilient hose attachment using recycled plastic pop bottles, that I will document one day, that makes this easy and scalable.

Inspiration

I have a Parkside wet and dry shop vacuum that already has this feature, but I don't want to keep it attached to the dust separator all the time as it's useful for other things. I watched quite a few youtube videos, and read a few Instrucibles and blog posts by others who had already made one, and decided it was worth a shot. After talking it over with my dad - a retired Electronics Engineer and life-long maker, he came up with the idea of using an AC current-sensing module.

Solution

A scavenged project box, with a single mains socket mounted on the front to power the vacuum; Inside, is a repurposed 12 volt power supply, an AC current-sensing module, a relay and two terminal blocks. I used an old, but sturdy, 4-gang mains extension lead, and cropped the cable at about a metre from the plug. The section with the plug became the mains feed, and the 4-gang socket strip became the feed for the monitored tools. A bank of 3x 1000 microfarad electrolytic capacitors across the relay keep it energised for a few seconds after the triggering tool is turned off.

Auto-on shop vacuum controller module inside, showing 12V power supply, relay, AC Current-sensing module and terminal blocks.

Bill of materials

Item £Cost Notes
Project box £0.00 Dumpster dived about 10 years ago
4-gang extension lead £5.00 Already had this on the shelf
Switched single mains socket £1.00 "Old new" from local charity shop
Low profile single back box £1.50
AC current sensor switch M3050 £8.59 Purchased on Ebay
3x 1000 μF electrolytic capacitors £1.77 Purchased on Ebay, 5 for £2.95
Terminal blocks - 11 terminals £~2.00 Already had, but cheap to buy. DC terminals are smaller than mains ones
12V 2A DC power supply £?.00 Free, recovered from junk pile years ago. Similar available on Ebay for approx £5.00

Wiring diagram

Auto-on shop vacuum controller wiring diagram.

Additional Features to be added

  • Swap out the 3 1000 MFD electrolytic capacitors for one larger one (my Dad says it's untidy as it is currently) - see update 2
  • Add a manual-on switch so I can turn the vacuum on without powering a tool or unplugging and replugging it - see update 1
  • An external indicator light maybe? - see update 1

Updates