Looking for automated blast gate options

[Anthony Whitesell]

I have seen Alan's pneumatically operated blast gates and I have seen a solenoid-lever operated version.

I would like to stay all electric so I don't have to run the air compressor. The WWing tools don't wake my daughter, but the air compressor wakes the neighborhood.

I'm pondering a lead screw design in place of Alan's pneumatic cylinders. Most DC motors are reversible requiring only two wires, but I haven't figured out how to stop it at the end of it's travel.

I wonder if there are any other designs out there. So I am looking for links or pics.

[Dan Friedrichs]

I also have been looking at this. I really like Alan's design, but don't want to run compressed air throughout the shop.

First, I considered using a lead screw and stepper motor, since you wouldn't need position feedback or limit switches. I couldn't find steppers that were strong enough.

So I went with a lead screw and reversible DC motor. I configured mine with a simple arrangement of 2 limit switches and 2 diodes, such that it closes when +12VDC is applied, and opens when -12VDC is applied. This way, I can run only 2 wires to each gate, and by flipping the polarity of the voltage on that wire, I can open or close it. Also, I don't need to feed back position information or anything else - once the gate hits the limit switch, it becomes an open circuit until the polarity of the voltage is reversed.

I briefly considered building these and selling them commercially, but just realized that they take about 2 hours each to assemble, and I don't want to spend that much time on something that's not for *my* shop. However, I did find that I could build these REALLY cheap (even using the HDPE shown in the picture below, the cost of all the parts, was about $10/gate). There's really nothing to it - a gate body, a motor, 2 limit switches, 2 diodes, and a handful of screws.

To power the gate, I'm presently building little control boxes that plug in-between a tool and the wall outlet. These control boxes will sense when the tool has turned on, and apply +/-12VDC to the gate motor. Again, there is hardly anything to these control boxes: a current-sense transformer, a relay, a small transistor, and a +12v power supply. I'm having circuit boards printed for this, so in the future, if anyone is interested, perhaps we can discuss doing a group-buy of parts for this (or something), as the quantity discounts are large.

Attached is a picture of a 6" gate. Also, here is a link to a video showing the gate in action:

http://www.youtube.com/watch?v=NGzJ5fpVsOQ

In the next few months, once I finalize the control boxes, I plan to do a large post here at SMC explaining all the details and including all drawings, schematics, parts lists, etc.

All that being said, I'm not sure I'm convinced that a lead screw is a great idea. I really like Alan's pneumatic gates. Consider that they really don't use much air - they just need a small reservoir. I think it may be interesting if someone built a system like Alan's, but used a small air tank in the control box, and a small DC compressor to top it off when it gets low (think something like one of those cheap cigarette-lighter tire inflaters). You need neither high CFMs or high pressure, so this would work very well. You'd get all the advantages of pneumatics (self-cleaning cylinders, etc), and avoid the noise/hassle of a big compressor being connected to it. However, I think the cost of the cylinders may exceed the cost of my all-electric gates by quite a lot.

[Jonathan Spool]

Anthony,
Check this out. I have been looking into it myself. My local Woodcraft uses them in their shop, and they seem to operate quite well, albeit a little spendy.
http://www.ecogate.com/

[Anthony Whitesell]

Interesting design. From one picture I can tell that the there is a pivot opposite the motor. The motor must have a gear on it that mates with the teeth on the moveable blind (you can see the teeth if you look closely at this lower photo here http://www.ecogate.com/industrial/gates.htm)

Anyone else have any designs or ideas. I'm trying to think out of the box.

[Anthony Whitesell]

I wonder if an airbrush air compressor would work? I think that's about the size you're thinking of.

I'm not particularily worried about the auto-on feature. My work area is setup with the tools along the outer edge of a circle due to the construction of the basement. So I'm planning on a central control panel. I have the circuit and parts already. Push one button to open the gate you want and all the others close.

[Dan Friedrichs]

I wonder if an airbrush air compressor would work? I think that's about the size you're thinking of.

I'm not particularily worried about the auto-on feature. My work area is setup with the tools along the outer edge of a circle due to the construction of the basement. So I'm planning on a central control panel. I have the circuit and parts already. Push one button to open the gate you want and all the others close.

That might work - I was just thinking of any generic little 12v compressor like this:
http://www.amazon.com/Industries-HV4.../dp/B000WG952Q



So you're planning on having to walk to a central panel and press a button to open each gate?
I won't try to talk you into it if you're not interested, but I think the auto-on feature would be very nice.

[Jeffrey Makiel]

Most pneumatic actuators need only 20psi or less to generate a couple of pounds of pulling force. And, since they are small and relatively well sealed, an airbrush compressor is likely more than adequate since capacity in not an issue.

One company (Del-Aire, I think) sold pneumatic actuator systems for garden model railway enthusiasts to operate their switch tracks. They used a simple 2 liter coke bottle pressurized with air to demonstrate the operation of their pneumatic solenoids.

Also, plumbing your shop would likely only require 1/8th inch or so plastic tubing similar to the stuff that comes with automotive air shocks which is generally rated over 200psi. The connectors and tee fittings use simple screw type compression nuts. Again, there is really no significant air volume associated with these class of pneumatic solenoids. This is all that is needed.

As for my shop, I used electric solenoids to flip a damper blade. Although I've had little problems over the 20+ years they operated, I would probably look at used pneumatic stuff now that ebay makes these parts accessible to hobbyists. Years ago, the cost of pneumatic switches (not the solenoids themselves), made pneumatic systems too expensive for my hobby use.

-Jeff

[Jeffrey Makiel]

Regarding 'auto-on'...

I've found that I often cycle my woodworking machines (like clearing the cut-offs from a tablesaw). However, I would rather keep the dust collector running instead of cycling it too. If you decide you really want an 'auto-on' feature, I would also recommend a way to have a 'manually-on' option too.

For me, all my actuator switches for my electric solenoid driven dampers are located right where I stand when operating the machine. It's about as simple and convenient as I desire.

-Jeff

[Dan Friedrichs]

Regarding 'auto-on'...

I've found that I often cycle my woodworking machines (like clearing the cut-offs from a tablesaw). However, I would rather keep the dust collector running instead of cycling it too. If you decide you really want an 'auto-on' feature, I would also recommend a way to have a 'manually-on' option too.

For me, all my actuator switches for my electric solenoid driven dampers are located right where I stand when operating the machine. It's about as simple and convenient as I desire.

-Jeff

I haven't got my system fully installed, yet, so maybe I'm not thinking of it correctly....but isn't the whole point of this to avoid having to take the additional step of opening the blast gate (or turning it on)? If I have to flip a switch to open the gate, why not just....open the gate? Is it just because your gates might not be immediately next to the tool for some reason?


I think that having the BLOWER turn on automatically is a bad idea, though (many times I might just be making one cut and will be done for the day before the blower even spins up) - do you just do manual control of the blower?

[Anthony Whitesell]

Walk is relative. Being 6' tall, my reach alone is 3' and a half step makes it 4-4 1/2'. My work space is in two sections with a wall in the middle. One section is 7x12 the other is about 5x12 (actually larger but my tractor is parked on the other half, it is 45 years old after all, so it gets some special treatment). With the wall in the center it makes it a perfect spot for a control panel. I also plan to locate a remote DC on/off switch with in the panel. Alan Schaffter recently re-posted his design for a mag starter/remote box switch panel which I'm going to adapt to my system.

Most of my blast gates are behind the tools which are located against the walls. So the extra steps come in walking (or squeezing) around the tools to open the gates.

I think that having the BLOWER turn on automatically is a bad idea, though (many times I might just be making one cut and will be done for the day before the blower even spins up) - do you just do manual control of the blower?

I don't think it's a bad idea as long as there is a off-delay time (2-5 minutes). This would allow the lines to be sucked clean while alsp providing an opportunity for you to have the next cut ready. Due to the combination of the work and home schedules, waiting for the tablesaw to spin up seems like an eternity sometimes.

[Alan Schaffter]

Dan- have you had a chance to test your gate when it is connected to an operating DC? Is there any trouble moving the gate with suction on it? That is the only thing I would worry about with the motor/lead screw actuator.

I think one of the small compressors would work fine with a pneumatic system. You could make an accumulator or two using 6" PVC as long as you don't exceed its rating. I'm using really cheap vinyl (fish tank aerator) hose for air since as someone mentioned you don't need much pressure - less than 20 psi will operate the gates easily, in fact I use flow restrictors to slow down gate actuation.

I also retained manual control from wall stations.

Eco-gate is WAY too expensive for my blood. Check these prices from their 2008 price list:

greenBox Control Panel (will control 12 workstations) $995
Clip sensor: $59 (basic toroid sensor $20)
4" 24VDC metal gate: $149
6" 24VDC metal gate: $380 YIKES!!!!

As far as the "auto-feature" that is why I built my gates. I never need to worry about opening a gate or turning on the DC. The gate at the machine I am using is always the one that is open- with only one gate open I have maximum suction at the source. There is only one situation where that is a bit annoying- when I'm drilling metal at my drill press and really don't need or want the DC on.

I wanted the blower to turn on automatically also, but designed it to stay on unless I turn it off manually.

Unless you have a BIG shop or are really quick on the switch, you don't need a time delay. At the typical 4000 fpm (67 fps) dust will traverse your ducting and arrive at the cyclone or dust bag before you even think about turning off the machine, do the math if you don't believe it.

[Dan Friedrichs]

Dan- have you had a chance to test your gate when it is connected to an operating DC? Is there any trouble moving the gate with suction on it? That is the only thing I would worry about with the motor/lead screw actuator.

Yeah, I did, and didn't have any problems. Those little DC motors are impressively strong - I'm curious (although not inclined to find out) what would happen if I got a finger pinched in there.

Mine were made from HDPE, but I think in terms of ease-of-assembly and cost, MDF/hardboard/plywood/etc would be better.

[Dan Friedrichs]

Eco-gate is WAY too expensive for my blood. Check these prices from their 2008 price list:

Clip sensor: $59 (basic toroid sensor $20)

That really annoys me. If you look at their sales lit on the clip sensor, you see that it's just two inductors and a small amplifier. Really, there shouldn't be any magnetic flux leaving an AC line cord to detect, so they detect just the slightest bit of fringing flux that leaves the wires. A neat idea (although I've read that it doesn't work all that well - unreliable), but the parts to build that sensor are literally less than a dollar. If they're charging $60 for it, they should at least get it working reliably....

[Jeffrey Makiel]

I haven't got my system fully installed, yet, so maybe I'm not thinking of it correctly....but isn't the whole point of this to avoid having to take the additional step of opening the blast gate (or turning it on)? If I have to flip a switch to open the gate, why not just....open the gate? Is it just because your gates might not be immediately next to the tool for some reason?


I think that having the BLOWER turn on automatically is a bad idea, though (many times I might just be making one cut and will be done for the day before the blower even spins up) - do you just do manual control of the blower?

My shutoff dampers are either located behind the machine or in between the ceiling joists above my head. I didn't want to reach around a machine to turn anything on. But, that's because I'm lazy. Having a system with automated blast gates (or dampers, in my case) is really a luxury item and just a fun gizmo for me.

Since my system uses 110V household current, I used simple lamp cord and toggle switches that could be located anywhere fairly easily. The toggle switch at each machine also activates a relay to power my dust collector.

As far as needing a time delay to clear the duct work of debris, I agree with Alan that it's not necessary for a standard home shop the size of a two car garage.

-Jeff

[Alan Schaffter]

That really annoys me. If you look at their sales lit on the clip sensor, you see that it's just two inductors and a small amplifier. Really, there shouldn't be any magnetic flux leaving an AC line cord to detect, so they detect just the slightest bit of fringing flux that leaves the wires. A neat idea (although I've read that it doesn't work all that well - unreliable), but the parts to build that sensor are literally less than a dollar. If they're charging $60 for it, they should at least get it working reliably....

I suspect the signal is very low level coming from those clip-on detectors. I had contemplated making my current sensor switches mobile- putting them in an enclosure with male plug & female receptacle for the machine with a low voltage cable and connector running to the gate. That would have allowed me to change the location to a different machine and blast gate. I decided that was not needed since. Though most of my machines are mobile, I will likely never move and operate them from a different location or outlet. Also, it is much neater looking to have all the magic behind the walls. One option I might incorporate in at least one gate location is to add another current sensor switch and mount a selector switch on the manual gate control plate- so I can select between two different sensed outlets (110V and 220V). That is the one advantage of having a centralized PLC type system. But, so far in over two years, I haven't needed to do that.

I think a retail autogate system that is cheaper than Eco-gate is possible, but it is amazing when you get down to every little component, assembly, etc, the costs climb quickly. I think it could be done using a small DC motor and leadscrew. Pneumatics would be too expensive. Though start-up costs for tooling, PCBs, molds, etc. might run in the high tens of thousands or more, I think production (and retail cost) could be kept down if it was manufactured off-shore. I wonder what the auto industry pays for the small motors used on door locks?

Such a system would need really inexpensive injection molded blast gates, etc. Based on the research I did for my high dust alarm enclosure (just a plastic box), the molds for a plastic blast gate could run $20K or more, but each gate might cost less than $5 (plastic parts only). Injection molding would allow for easy assembly with integral mounting tabs/brackets for the motor, leadscrew/followers, and limit switches, and if designed properly might provide all gate components with protection against dust. Amortized development costs, materials (PCB and components, DC power supply; enclosure; male/female power connections; low voltage cable and connections to the gate; etc.), and manufacture (etching, surface mount components installation, including toroid sensor; etc. wouldn't be cheap but probably less than the Eco-gate system. It would probably need U/L certification. Making it a standalone unit would make it more attractive to potential customers since a master control box would not be needed and the woodworker could build a system gate by gate as money became available. Control of the DC if desired could be done via wireless, which could be designed as a user-installed add-on. With a clip-on sensor system, you locate the gate at the machine but would need a separate power cord.

Just thinking out loud.