It’s A Hack: Air Scrubber Controlled Using The Room Lighting

Jet tools air scrubber

Some products just seem to be designed to be annoying. [hardmar] discovered the air filtration system installed in his son’s basement woodshop was orientated for the best airflow, but rather poorly positioned to actually turning the thing on and off. For some reason the unit has its single line-of-sight IR receiver on one side, which when mounted in some positions, forces the user to be the completely wrong position to use the supplied remote.

We find it a little unhelpful sometimes that devices specifically designed to be mounted with varying orientations don’t come fitted with IR receivers in different locations to ensure good controllability. It would get annoying really fast to have to contort oneself into some specific position just to turn something on, and some people just might not bother at all.

Proper control of dust is paramount for continued good health, and essential in any workspace or shared area. When you work wood, it produces a lot of dust. It cannot be avoided and gets into everything, your lungs included. PPE is not enough.  Even in your own shop you still really should manage dust production as best you can. Options are varied from centralised extraction, per machine solutions, and often augmented with air scrubbers mounted on the ceiling to grab those fine particulates.

Instead of solving the IR placement issue, [hardmar] wanted to have the unit tied to the lighting system so that it would power on as soon as someone turned on the appropriate light and would then stay on for a fixed amount of time after the user left in order to continue scrubbing the air some more. His simple hack was to first record and analyse the IR protocol used by the remote, and program an Arduino to be able to send it on/off commands. Next, he hooked up a phototransistor aimed at the light, in order to provide the necessary ‘user present’ trigger to tell the Arduino when to activate the scrubber. Super simple and effective. We love this non-invasive approach of adapting off-the-shelf equipment to our specific requirements, without even showing it a screwdriver.

As [hardmar] admits, the hack is not elegantly implemented, it’s just enough to make it work, and that’s just fine, sometimes you just have a job to do and no more.

8 thoughts on “It’s A Hack: Air Scrubber Controlled Using The Room Lighting

  1. Not to cast aspersions on a good hack, but wouldn’t a small mirror close to and behind the unit give access to the IR channel from the front? IR will bounce off of a lot of things, a white-painted surface would probably work.

    I would maybe take a piece of glass rod, heat it up, form it into a U-shape, and mount one end at the receiver and the other facing where it’s convenient to control the unit. Maybe acrylic rod would work as well.

    Also, they sell dual-head IR receivers on eBay for less than $5, and repeaters for under $10 (powered by any USB wall wart).

    (The unit has a built-in timer that can be triggered by the remote.)

      1. Glass absorbs far-IR, like thermal radiation, but usually not the near-IR used for remote controls. Camera lenses commonly require special coatings to block this near-IR, and if you have an somewhat older phone, you can see the IR from a remote control with the camera, through a glass or acrylic lens. Newer phones have better filters, specifically to block this light, because glass doesn’t sufficiently absorb it.

        A light pipe may require less space than a mirror, and provide more freedom for the positioning of the receiving end.

        Still, this solution has the added benefit of turning the unit on automatically, so the user can’t forget to turn it on, assuming the workshop is such that the artificial lighting will always be used and other light sources don’t interfere with the detection.

  2. I plug my fan into the light circuit. Light on = fan on. Light off = fan off.
    Installing a receptacle is faster and cheaper than frigging with an arduino. More reliable and better longevity too.
    I turn the fan off with its own switch if I don’t need it.

    1. Agreed. Part of the problem with this particular unit is that it can’t be activated just by applying power. It can only be turned on by pressing the soft control buttons on the built-in control panel or by using the IR remote. The user could have definitely looked at bypassing that soft control and just having it turn on when power is applied, but maybe that would have been more complicated depending on what type of motor the unit has.

      In any case, it seems odd that the KISS principle seems to fine for the manufacturer making a vacuum cleaner (power switch, fan, filter) but for some reason this dust filter needs more “features” that seem to just make it more complicated than it needs to be.

      If the unit could just run on power up, the delay-off feature of this project could be implemented with a simple timer relay triggered off the light circuit. It would require two power circuits (one for power to the unit that is separate from the light circuit), but the resulting system would definitely be simpler. Lights turn off, relay keeps unit powered for x number of minutes, relay turns off unit.

  3. “We find it a little unhelpful sometimes that devices specifically designed to be mounted with varying orientations don’t come fitted with IR receivers in different locations to ensure good controllability”

    Honestly I think I have never came across a device with multiple IR receivers. I think it is not trivial to make such a device that works reliably as each receiver may receive at least some part of the signal and so require some arbitration mechanism to make it work.

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