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Simple circuit, switching vaccuum on with power tool

Discussion in 'Electronic Design' started by CampinGazz, Feb 20, 2004.

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  1. CampinGazz

    CampinGazz Guest

    Firstly, from my last posts you can prolly gather I can build a circuit if a
    circuit diagram is available, I just need help getting to that stage with
    what components to use and how to connect them...

    For my next project, I have a load of woodworking tools I'm going to be
    using for the next 3 months as I build a motorhome, they are mainly small
    tools, router, sanders, biscuit joiner etc, plus a bandsaw and a table saw,

    I have an old vacuum cleaner I'm going to use for collecting the dust
    produced by the tools in use, but it's a pain to have to keep switching it
    on and off before and after I use the tools,

    So I want something like a 2 way extension lead, plug the tool in one
    socket, and the vacuum in the other socket, when the tool is turned on, the
    vacuum starts up, tool off, vacuum off.

    I know you can buy vacuum cleaners that have this function built in, but
    they're not cheap, and I already have the vacuum I want to use, also they
    usually have a limit of 1800 watts for the tool plugged into them.

    The table saw pulls 2500 watts or there abouts, it's an induction motor, so
    will have a much higher start up current, (were on 230 volts here)

    So I imagine with the vacuum cleaners with the power take off built in, they
    use something in series with the tool to be used?

    What can I use that doesn't limit the power of the tool that switches the
    vacuum? vacuum motor is 1200 watts.

    The smallest tool I'll use pulls 30 watts, largest pulls 2500 watts,
    Should I be looking at something like a ammeter type circuit using a pass
    through coil to detect the current to switch a suitably sized mains relay
    (not sure of the terminology there, but not using a shunt, inductance
    measuring of the current? like a clamp meter does), or should I be looking
    at a high current triac?

    Ideally I'd like something that doesn't have to pass the power of the tool
    through it to switch the vacuum, so I could use it with other things that
    need something turned on when another item starts up.
     
  2. Jamie

    Jamie Guest

    you need a current transformer..
    http://www.crmagnetics.com/newprod/ProductView.asp?ProdName=CR8750
    look at that.
    :))
    simply pass the high leg(black) through the hole and use the
    output and signal a solidsate relay to drive a large contector that
    will run your vac when ever you produce an load 2.5 amps or more
    through that current transformer.
     
  3. Ken Moffett

    Ken Moffett Guest

    I did this for my shop.

    I built a power-on detector using a homemade current transformer, some small circuitry,
    and solid state relays. It will turn on with about a 100W power draw. Because of the
    locations and number of circuits available, I had to run my table saw and vacuum on the
    same circuit breaker. Starting both the saw and vacuum at the same time would
    occasionly pop the breaker. So, I added in a turn-on delay of 2 seconds for the vacuum.
    Also, I added a delayed-off of 10 seconds for the vacuum. It continues to collect dust
    until after saw stops spinning. I also added a knee switch so I didn't have to look
    down and hunt for the little on-off switch they come with. And, since I was at it I add
    a pendent switch, with a coil cord, to clip to my belt so I could start (or stop) the
    saw from over 8 feet away. This makes it easier (and safer) to control the saw when I
    need to rip long stock. This is what electronics techs do in a wood shop! :)

    If you're still interested I could email you a copy of my sketched schematics next
    week. They could be simplified.

    This said, I think Rockler or Woodcraft sell a remote on/off control that uses a small
    key-fob transmitter to start a vacuum. I think they are around $50. If you had to buy
    all of the parts "new" for my control it would probably be more than that. Also, if you
    have never considered a knee switch, do. These are also available as after market
    add-ons.
     
  4. Ian Stirling

    Ian Stirling Guest

    You may find that altering the dust collector helps a lot.
    I really like one made from a large plastic barrel with a plastic top.
    Hoover top mounted to the barrel, hose coming out the side about halfway
    up, and a plate a little bit under some doubled over bedsheet makes
    it clog a hell of a lot less often.
    If you'r clever, you can do the above using an old bin, which lets you
    use binliners for easy collection of sawdust.

    I'll leave the actual question for others to answer, as it seems they are.
     
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