Auto Vac

This past year I have been reorganizing my shop … like I always wanted and never had time for.

I have learned two important things:

  1. If my tools are hung where I can see them there is a better chance that I use them, return them to their assigned place and don’t buy duplicates. note: I use french cleat walls and I have been very impressed with how easy they are to build and use.
    2. If my vacuum system is easy to turn on and adjust the gates I will use it, if not I find an excuse to think “its only a small cut”. The dust builds up!

note: since my shop is in two locations in the basement & garage a central system is not practical. Instead I have used area vacuums with RF switches on them. This includes single vacs for isolated tools.

Now the reason I wrote this.

In one case I have a drill press with a dedicated small vacuum. I find that I forget to turn the vac until I start drilling. Usually I have on hand on the spindle feed and one on the piece so I just finish the hole and am annoyed by the debris the vac was supposed to remove.

I decided to solve this by building a vac control that senses the tools current and then turns on/off the vac.
This build uses these parts that are all packaged in a power box.

  • an Arduino nano
  • ac current sensor,
  • off line 5v switcher
  • switch
  • relay

Also, much less expensive than the store bought ones.
If there is interest by others I will go through the effort of documenting what I did and sharing it and the code.
I am thinking about making a version that turns on a vac by monitoring current from multiple tools…


That’s really cool. It would be great to see the build documented.

So you will build one :)?

I would give it a try. I have yet to play with Arduinos so this would be a great way to learn something new.

ok then I will get on the documentation.


I would probably build one also. Devices like this just Makes a shop all that more efficient noise-wise, which some don’t consider when using a shop. Soo many tools are loud(vacuums included), so any way to toggle these on/off as soon as their not needed should be mandatory :slight_smile: Extra insulation in the walls doesn’t hurt either im told…lol


Here is my reworked version of the vac control.
Bigger box more features easier to make
After using the proto I realized that it would be nice to turn on another device besides the vacuum, like my drill press light.

  • 4 way box for more room and easy wall mounting
  • Aux plug always on
  • Tool plug (where current is measured)
  • Light plug (comes on with tool)
  • Vacuum plug (comes on with tool)
  • Acrylic sub-plate for easier assy and some isolation
  • All amazon and big box store parts
  • Easy usb port access for programming
  • Nano in socket for easy replacement
  • Large capacity AC cord and gland

Video, docs & code coming next


Looks like this but yours has a few more whistles and bells

That is an AC relay that is controlled by a digital signal. It has no current sense or smarts!
My controller controls 2 outlets based on the current drawn from a 3rd.


I like this approach. It’s sophisticated and extensible.
What I’ve done in a similar situation is use an inline foot switch, because I want to have both my hands on the work sometimes. (Feeding a sheet of plywood into my tablesaw being an obvious case.) Where I need a vacuum, I have the inline foot switch go to a power strip that the vacuum and tool are plugged into.
There’s a significant safety hazard with this, in that something that falls could land on the footswitch and turn on the tool while you’re not even there. Your solution seems inherently safer.


In regard to extensible, I am thinking about a version where multiple tools can start the vacuum using this same design. It would use multiple current sensors connected to a central unit.

1 Like