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  1. #16
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    Quote Originally Posted by arniew View Post
    I’ve been happy to let go of RC circuits for timing and instead flash code to a controller. Much easier!
    That depends on how lucky you are. I found a bunch of Omron delay timers and mounting blocks during council pick up and wired one via a relay to the DC switch. When I turn the DC off it can be off immediately or go via the delay timer. The delay time can be manually adjusted from zero to 20 minutes. This was much quicker than setting up an MC to do the task. However if I was already setting up an MC to control gates etc then I would go via the MC for controlling the delay off.

    What length of delay do you suggest for a DE and what about an air filter in addition?
    The delay depends on the usual suspects which is why an adjustable timer is handy
    - length of time of completed dust generation activity
    - type of dust making activity
    - size, effectiveness of DC dust capture
    - extent/effectiveness of other ventilation
    ETC

    Using a particle counter to measure the dust here are a couple of examples
    A single TS cut of pine with a 3HP or more DC with an effective OH guard, 30s should be enough
    Half an hour of ripping dry hardwood with a stock 2HP DC, no ventilation and a crappy OH guard, this needs about 30 minutes to clean up the air in a shed.
    Sanding usually requires longer delay times and using a drill press the least - can get away with zero on this.

    To save adjusting back and forth all the time I use a standard "delay off" time of 2 minutes, But I have 1200 CFM of additional forced ventilation that also runs at the same time as the DC. 2 mins covers all activities except longish periods of sanding - then I increase the time to 10 minutes.

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  3. #17
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    FWIW I have done a 2 minute default run on timer for my system as well and since implementation, the sewing room for the mistress of finance went from pitch forks and voodoo dolls to hardly any evidence. That's with a 2HP system, 150mm duct and bell mouths inlets modified as per the sticky on this topic.

  4. #18
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    Quote Originally Posted by BobL View Post
    Some interesting ideas there.

    A gravity return might work by orienting the gate so that it slides in the vertical direction and then just adding weight to wither the top or bottom of teh gate.
    This assumes there is enough space for the gate to work in the vertical direction.

    I'm not familiar with the Clearvue gates but most gates I have seen have stiction issues sometime during their life so weights might have to be quite large to over come this.

    Rocker style gates gates operate in a horizontal/rotary direction so if your motors have enough torque you might be able to go back to your original rotary approach.


    The same microswitch might be able to be used to tell the program what gates are open and closed.


    DE shouldn't be used just when a machine is running but run for some time after the last dust making activity to help clear fine dust.
    Some time of timer should be added wither as a physical timer to the circuit or in the Arduino program.
    I’ve been thinking more about rocker style gates. If I can successfully drive one with a servo, micrswitches aren’t necessary for position feedback.

    The challenge is minimising friction/load on the gate to allow a regular servo to drive it. Bigger servos are available but pricey.

    Any bright ideas about a good gate material (ie. the moving part) that will hold its form against DE suction when closed, but is also lightweight and has a low friction surface?

    I’m thinking maybe a thinnish plastic might work, or maybe 3mm Masonite or perhaps one of those cardboard boards that are both light and rigid, maybe from an art supply place.


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  5. #19
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    Rocker style BG's could be driven from the pivot point, the moving blade would have the shaft fixed to it. A bell crank attached to the shaft and driven by a pneumatic cylinder electrically operated would be a good start point for design. Limit switches in the BG would be necessary I reckon to avoid tearing the shaft out of the blade. I have a few rocker gates on remote string controls but sometimes it is difficult to position them so the strings can move the blade through its total travel. My rocker gates are made from 9mm MDF and if the cyclone is running they can be very difficult to open with the string controls if all other BG's are shut so I have to open the rocker gate before closing the unwanted BG.
    CHRIS

  6. #20
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    Thanks Chris. With the right length levers I reckon a linear actuator might do the job without need of extra limit switches.


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  7. #21
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    I have tried making rocker gates bits and pieces out of, Al, MDF, melamine, HDPE, PVC.

    No matter what they are made of, if the material is too thin they can twist and thus increase friction.

    The worst ones by far were the all Al ones as the Al on Al has fairly high friction, once they get scratched they rapidly get worse. This effect can be reduced by increasing the clearance but then will leak.

    Raw MDF works quite well but I would be worried long term. They could be sealed but its a lot of work.
    Thins sheet material will twist. The best ones I have seen were made by Bunbury Mens shed where they used 9mm MDF for the body and rocker and 12mm MDF for the flange..

    PVC sheet also works well but is expensive, thin (3mm) sheets twists easily and thicker sheet (6mm) is very expensive.
    in teh thread referred to below I show some PVC rockers - the text says they're made of 3mm PVC but its 6mm PVC I got out of a skip.

    I have used 3mm HDPE and Melamine as rockers and these worked well.

    For more ideas check out Blast gate gallery

  8. #22
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    There has been some comment on the blast gate gallery thread about automating gates. As this is a bit off topic for there, it seemed better to revive this thread.

    In particular, responding to this quote:

    Quote Originally Posted by BobL View Post
    Sure.



    Yeah I've thought long and hard about this approach as well (I collected a lot of micro switches from washing machines and driers by the sides of the road expressly for this approach) and I reckon it would be useful if the ducting system was simple enough with the following considerations.

    A gate status indicator (GSI) will tell you if the gate is open or closed, but then so will looking at the gate? That's problem #1, remembering to look at the gate and more importantly #2 doing something about it - I have often looked at a closed gate and said, "Nah - just this one cut", etc

    Either gates have to automatically switch (and if required start the DC) when a machine starts, OR an alternative is a device whereby a machine won't start unless the DC is on and the right gates are open.

    Gates or GSI's located further back in the shed also may not be seen from all places in the shed, then multiple GSIs might be needed for the one gate.
    What a simple GSI won't indicate is if the DC is on and if the DC is outside, machine is on, operator is wearing muffs the DC cannot be heard.



    Yeah costs add up rapidly when there are more than just a few gates.
    The worst case scenario is of the 15 gates in my shed I need a minimum of 10 to be in the right state for my TS to efficiently collect dust.
    The gates controlling the branch going to the TS, the branch going to the TS OH guard, the gates on the OH Guard itself and under the TS cabinet, must be ON
    The gates controlling the branches going to the Lathe, Bandsaw, Beltsander, DP, Router, Thicknesser/planer, Power tool takeoff and table/bench sweep must be OFF.

    This is why a simple single pressure switch (and in the case of the TS its 2 switches - one for the cabinet and one for the guard) near the TS is able to keep the TS from running until I have all 10 of the gates in the right state.

    Despite all this, as Chris Parks knows I like it when I am proven wrong , so I still encourage you to have a go, but now I have hopefully given you a heads up of where some of the pitfalls are.
    I have thoughts about a simple way of sorting out a feedback system, and a more complex way.

    THE SIMPLER IDEA:
    On each blast gate, have a microswitch for the closed position, indicating if a gate is fully closed OR anything but fully closed.
    Manually opening/closing the gate, therefore ensuring an open gate is fully open when needed.
    Using the switch feedback to give visual feedback near the control gear on each machine (and possibly on a central indicator panel).
    On each machine is a two-colour LED. Green means the gate(s) for this machine are open and no others are open. Red means this machine gate(s) is/are not open. Flashing Green means this gate(s) is/are open but some other gate(s) is/are open.

    Switches on gates are inputs into a simple controller (ie. arduino)
    Controller automatically switches DE on when needed.
    A bit of code determines run time of DE depending on machine used and user experience.

    THE COMPLEX IDEA:
    The visual information will probably be the same but the gates are automatically opened and closed.
    Auto switching of DE as above.
    Each machine has switch or current detection feedback to the controller to indicate demand.
    Each blast gate has some form of motorised control system (in my case electric as this is my area of expertise/interest).

    My feeling is that the most practical version of gate to automate is the rocker style.
    I have a linear actuator to test one method of controlling a gate.
    I think a motor driving a linear gear (actually curved on the rocker) is likely to work better (similar to GRNGATE).
    A linear actuator won't need feedback (other than over current) to indicate limits in travel.
    A geared motor with linear track could use current sensing to indicate travel limits (or blockages).

    * my feeling is that the simple idea would prevent the common issue of having no or too many gates open and should be quite easy to implement
    * the complex system is perhaps desirable if it can be done within a reasonable price limit, but is more complex than need be. I do like complex solutions though!

    I'm currently working on a dust extractor installation in a new shed and have done some work towards the simple option. The complex one is a maybe, one day idea.

    I'd be happy for thoughts on either/both of these ideas.

  9. #23
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    I have thought for a while that driving the shaft of the rocking gate might be a solution as the required rotation movement is minimised. It could be done by direct coupling a motor to the shaft or a gilmer (cogged) belt drive if the components were easily obtained.
    CHRIS

  10. #24
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    Should be straightforward to setup but i'm not convinced a red/green LED would be motivation enough make sure the right gates were open so the DC is on. Maybe OK for a conscientious DIYer but I know some blokes at my mens shed wouldn't care if another gate was open still allowing the DC to run, they would just ignore the red LED on their machine and use it anyway. Some are too doddery to know or don't even care if the DC is on.

    Even for someone like myself who sort of cares about dust, in my shed I still sometimes get carried away and am in too much of a rush to bother making sure the DC is on and the gates open for short jobs. Problem is, after a while all those short jobs add up and so then does the dust.

    To be 100% effective, the power to each machine being used needs to be somehow physically linked to the machine's gate position as well to the DC. I reckon doing it through the operators head is not fool proof enough. This then requires using either something like a current sensor on a machine switch to auto turn on the DC and open the right gates, or the reverse, a pressure sensor on the machine's immediate ducting that prevents machine use unless the DC is on and the right gates are open.

    All of my pressure switch boxes have an easily accessible "by pass" switch on them so when a machine fails to start ( ie pressure switch is not activated because either the DC is not running or the gates are not closed or both) I could easily switch the "by pass" but somehow I never do unless it is necessary. The fact that the machine does not start seems to jog my consciousness to do something for my health. At the mens shed the by pass switches are buried inside a screwed shut control box so the ning-nongs can't easily by pass the pressure switches.

  11. #25
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    Quote Originally Posted by Chris Parks View Post
    I have thought for a while that driving the shaft of the rocking gate might be a solution as the required rotation movement is minimised. It could be done by direct coupling a motor to the shaft or a gilmer (cogged) belt drive if the components were easily obtained.
    I plan to drive mine directly from the gearbox shaft. Either using a standard dc gearmotor or a stepper gearmotor. For open and closed indication/feedback i'll use hall effect sensors. Anyway that is if i get the time to play with it

  12. #26
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    Thanks Chris Parks for the Gilmer reference - that gives me another idea when thinking through the mechanical challenges of this. And ericks2, I'd thought about microswitches but hall effect sensors are likely to be more reliable long term. BobL, I think the simple system would work for me but I understand the challenges of different environments, especially a multi-use space like the Mens Shed. If I had all the time in the world I'd go with a fully automated system first up, but I think I'll have to aspire to get there over time.

  13. #27
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    Quote Originally Posted by ericks2 View Post
    I plan to drive mine directly from the gearbox shaft. Either using a standard dc gearmotor or a stepper gearmotor. For open and closed indication/feedback i'll use hall effect sensors. Anyway that is if i get the time to play with it
    My experience of stepper motors is that they tend to have significantly less torque than other motors. That means they can easily slip a step when under stress.

  14. #28
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    As well as an LED maybe add something a bit more annoying like a loud buzzer or alarm as this would probably be more motivational (ie you'd take an active step to get rid of it) than an LED.

  15. #29
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    What about using an electric window winder. Should be cheap enough from a car wreakers and is already set up to open (or close) all the way with a momentary contact.

  16. #30
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    Quote Originally Posted by arniew View Post
    My experience of stepper motors is that they tend to have significantly less torque than other motors. That means they can easily slip a step when under stress.
    That is why i will be testing the geared stepper motors that i showed in the image. I bought them initially for use on a tennis ball machine mechanism, they worked quite well.

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