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The best automated system I have seen installed never turns the cyclone off, start the machine and the BG opens, stop the machine and the gate stays open for a pre-set amount of time. All without a computer but they had to have a PC board custom manufactured.
https://mastslav.weebly.com
Chris
Everything I like is either illegal, immoral or fattening
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That is a nice system, but, in reality you shouldn't normally need a delay in the blast gate or DC control. What you are theoretically trying to avoid with both a delay-on-close blast gate and/or delay-on-off DC control is to ensure all dust and chips reach the cyclone and have an opportunity to separate before air flow slows/decreases or stops.
Some may remember that my system which has been operating great for 10+(?) years relies on homemade electrically controlled/pneumatically actuated gates (and a long cone DC) triggered by current sensor switches at each machine outlet. The current sensor switches (simple torroid + internal PNP/NPN transistor switch from CRC Magnetics) control SMC 5/2 pneumatic solenoids directly- no PLC and no circuit boards or any other circuitry except one transformer for the entire system.
I had thought about delay-on-close or delay-on-off but did the math and determined it was totally unnecessary- measure the distance from the cyclone to the farthest machine, then divide that by the typical airspeed in the duct to see how long it might take dust to be "processed." You'll find the time is EXTREMELY SHORT, and shorter than it normally takes me to safely finish the operation (e.g. clear the stock and cutoff from a tablesaw) and turn off the machine.
Someone please check my math, but assuming for arguments sake I am seeing only a modest 350 cfm (5.8 cfs) flow at the farthest blast gate from my cyclone. I use 6" duct (28.27 in² or .196 ft² cross section) so my airspeed at that point is 30.5 fps. It will take dust just a tad over 1 second (1.15 sec) to reach my cyclone 35 feet away. If I am shutting off my machines that quickly after an operation, I'm working at an unsafe pace!!
Contributor
Very true Alan, in addition the cyclone deceleration time will be much in excess of 1 second so the gate closing time wouldn't be an issue...Rod.Originally Posted by Alan Schaffter
I have increased my off delay timers on the routers so I can sweep dust left on the table into the router after the bit stops. Works well for me.
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But you still need to wait until your router spins down, to avoid routing hands and fingers!
If I need to do that I can just push a manual gate button (which also starts the DC.) I have one at each gate. I would post some photos but they are located on NCWoodworker where the photo gallery has been down for a few weeks now after a software "upgrade."
Update- I figured out a way.
Initial prototype- a modification to an existing machine-mounted gate:
Some of the raw materials- experimental homemade cylinder (didn't work), basic blast gate, SMC solenoid valves in a manifold:
Blast gate production line:
Two 6" and one 4" autogate installed behind a knee wall. Outlet covers will have manual buttons (all the magic is behind the walls!):
Duct being run for overhead tablesaw pickup:
Manual gate switch with status indicator:
Updated old gate behind the knee wall:
Under-floor autogate for tablesaw:
SMC 5/2 solenoid valve- 24volt (bell) wiring and vinyl air tubing- the operating pressure is only 12 - 15 psi. Uses little compressor air. Other widgets that came with the solenoid valves- muffler/air filter on the right. T fitting on the right with orange ring is a (needle valve) flow restrictor- without it the gate slide would be an effective guillotine! Really!!
CR Magnetics current sensor switch- small twisted orange and black wires are 24v that go to the solenoid valve. Single black wire passing thru toroid is one leg of a 220V outlet circuit.
Last edited by Alan Schaffter; 12-14-2018 at 9:06 PM.
Member
Corrimal Mens Shed turn the cyclone on when they arrive and turn it off when they leave 8 hours later so it runs continuously all day. I was going to copy their system until we worked out that using a VFD we can use two wires and a switch which is far more simple. The ramp up and ramp down time can be custom programmed and the one I installed the other day can be controlled from the bast gates, remote control, VFD or an isolation switch, all with a couple of wires and no additional electronics. We have found that VFD's simplify things to a huge extent on the control side and make running the DE far more flexible. I for one would never willingly install a system without one now.
Chris
Everything I like is either illegal, immoral or fattening
Contributor
Alan — What model CR current sensing switch are using in your setup? I really like the relative simplicity of your approach for automating the blast gates, especially from a 240V machine with a magnetic starter. Thanks for sharing.
-Tom
I tried the same CR magnetics current switch and it didn’t develop enough output voltage for the loads I’m dealing with. So, I switched them out for a different device I bought last year when I was sorting out my design.
The device I’m using is a Veriz Industries Hawkeye H608 split-core current switch with adjustable trip point. Works great even on a very low current load. Still fits inside a 4 square box and is adjustable. I found them on ebay for $10/ea shipped.
Tom - I'm sure I still have the CR Magnetics CR9321-PNP current switches. I didn't use them. I'd give them to you if you could use them. Email says I should have three of them.
Last edited by Steven Wayne; 12-14-2018 at 9:53 PM.
Member
It has been quite a few years- I had to search the SMC archives to find the photo at the link below. CR 9350 (NPN) (the difference between the NPN and PNP switches is where you intend to locate the load. https://sawmillcreek.org/showthread....t=CR+Magnetics
When you run a current carrying wire thru the center of a toroid a current is generated in the toroid coil. The amount of current depends on how many coils are in the toroid and number of loops of the sensed wire that run through the center of it- All my machines, with the possible exception of the router table, required only one loop of my 120v and 240v circuits. I don't remember but may have needed to run two or three loops of the router's wall outlet wire through the toroid.
It is possible to use the small amount of current generated by a toroid (no PNP/NPN transitor) to trigger a sensitive circuit or PLC, but that increases the complexity and cost. In my setup, the current causes the integral PNP or NPN transitor to change state, which switches the external 24 volts used to operate the solenoid air valves. The only problem going direct like I do is that the current rating of the PNP/NPN switch may be limited. Fortunately for me, my solenoid valves draw around 63 uA @ 24 volts DC and the NPN/PNP switches are rated at 120 uA @ 24 volts DC. If the solenoids drew too much current I would need current sensor switches with a higher current rating or use a relay or something else to power the solenoids.
One interesting (annoying?) feature of my setup. When I turn on my drill press work light the blast gate opens and and DC starts. I guess I need to put a separate cord on the add-on light.
Contributor
Steven — Thanks kindly for the offer. I’m months away from tackling this project so probably best to hold onto them for now.
-Tom
Just passed two years with the automated dust collection. No failures, no issues. It has worked out really well. Turn on a machine and use it, with the full force of the cyclone collecting all of the dust. Quite happy with the whole thing!
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