Dust extraction – Part 4: Solid State Relay

In this part of the dust extraction build I will show the solid state relay that is used to drive the vacuum cleaner.

I could make this part of the project with a PCB with a triac and optoupler etc, but decided not to do this to save time. Instead I used an off the shelf SSR-40DA solid state relays.

During use this component will get hot, therefore I mounted it to the side of an aluminium enclosure. In this enclosure I also mounted a grommet for the power input, a grommet for the signal wire and a power socket for the output.

Inside soldid state relais module
Inside soldid state relais module detail
SSR front panel

The box mounted near the vacuum cleaner:
SSR Mounted

Links to previous parts of this build:
Dust extraction – Part 1: Valves
Dust extraction – Part 2: Current sensor
Dust extraction – Part 3: Central Unit

The next part of this project will be the instalation of the tubes / hoses


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    • Sleepwalker3 on May 22, 2020 at 22:52
    • Reply

    Most wiring regulations, and just general safety precautions, say that you should be Earthing the lid also.
    Something else to watch is that any logos,numbers, etc. cast in the case where the SSR mounts, should be below the surface, otherwise the SSR will not make good contact. A logo is visible under the SSR,but it’s not obvious if it’s raised or sunken into the case
    Interesting build though, thanks for publishing it. 🙂

    1. Hello,

      The earthing of the lid is only necessary when the resistance to the earth connection can not be guaranteed to be below 0.5 Ohm. In case it was painted, a wire was indeed needed, however it is bare aluminium and it makes enough contact at low enough resistance.

      For the mark in the middle of the enclosure you are right. It changes the thermal contact of the SSR. In this case it is lower, so it should not be a problem.


    • Fard on January 15, 2023 at 11:56
    • Reply

    Hi sir this is fantastic I looking automatic shop vac but unfortunately really expensive in UK I did research and find your idea , just can’t find wiring diagram for this.
    I really appreciate if you can send me please.
    Also is this work only with one tool like table saw or can contact table saw and mitre saw?
    Thank you

    1. The project is not finished yet (not enough hours in a day at the moment), so no complete schematics firmware yet. But in part 2 the current sensor is a schematic of the current sensor. The “to central unit” signal can be used to drive the (solid state) relays.


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