Dust collection switch for a woodshop

I am currently starting the planning stages for my first arduino project, and first serious electronics project. While doing basic research on electronics and micro controllers for the past few months I've also been thinking of a simple yet functional project which I have just decided on. My wood shop has a 110v centralized dust collection system connected to 4 large stationary power tools (115V 14 amp band saw, Router table, Miter saw, and a 220V 15 amp planer). My goal here is to create a switch that will turn on the dust collector when any of those tools are turned on, and keep it on for 5 to 7 seconds after the tool is turned off. I have circuit diagram for a significantly simplified system that does not do the timed extension, is only connectable to one tool, and is not capable of 220v but moving this from tool to tool would quickly negate the convenience it is meant to offer.

I'm mostly checking to see how difficult this will be, how much it will cost, and how worried I should be that I will burn down my garage. I am very familiar with general home electrical work and have done some simple breadboard projects but haven't done much else of the small stuff so any and all guidance is welcome.

Thanks

Hi, welcom to the forum.

You have to know how to handle the mains voltage in a dusty environment.

The input can be a Current Transformat (CT), that is a core with coil around a single mains wire. It is isolated from the mains. It might even be possible to turn on the dust collection system if the total current of the workshop is above 5A, or something like that.
Here is some info: http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
You could add an Ethernet Shield and show the current of the workshop in a graph on internet.

The output can be a relay or a solid state relay (search on ebay for SSR-25DA or SSR-40DA).

With a CT for input and a relay or SSR-25DA the Arduino is safe from the mains voltages. However the wires should be protected agains the dust. With such high currents for the tools, the wires to the Arduino could pick up some nasty spikes. Perhaps some protection is needed for the Arduino pins.

The CT is a great input for this application. If you run a circuit for just the tools and only the tools, then you can use one sensor to detect when the tool turns on right on the main, otherwise you will need one for each outlet or each tool.

For larger motors relays and solid state relays (SSRs) are not really the best choice. A motor contactor or soft start motor controller is best. Most are for three phase motors but can be used on single phase 110V with one hot leg, or 220V single phase with two hot legs. You can usually get them from eBay for little money. The drawback will be they are usually 24VDC drive, so you will need to add an output drive chip (ULN2003 or ULN2803) to drive the load.

With the same type of CT, you can add one to the dust collector and read, calculate, display the motor amperage, and even shutdown if the Arduino detects the motor is drawing too much current. Which is very important to not overheat the dust collector motor.

I am hoping to do the same project this winter.

I looked at the same thing, decided a commercial product was the way to go.
.

All the tools (including the dust collector) are on the same circuits, with the exception of the 240v planer. The issue comes to mind that once the CT is triggered the collector would pull enough amperage to continuously trigger it. I assume I could change the collector to run on the same circuits as the lights but will have to check how easy that will be. Appreciate the help guys keep it coming.

giser3546:
All the tools (including the dust collector) are on the same circuits, with the exception of the 240v planer. The issue comes to mind that once the CT is triggered the collector would pull enough amperage to continuously trigger it. I assume I could change the collector to run on the same circuits as the lights but will have to check how easy that will be. Appreciate the help guys keep it coming.

The more I think of it half of the design is cased on how the shop area is wired. If the DC is on the same circuit as the tools, the CT cannot be installed on the main feed before the first outlet. A CT will need to be installed at each outlet, but only if you have a trunk line-drop wiring style. If the wiring is daisy chain, the CT will need to be put on the tools cord. So rewiring of your shop may be required. When you start looking at woodworking tools, it becomes readily apparently they are power (amperage) hogs. If you move your DC to a separate circuit it will allow you to go bigger on either your tools or the DC.

The output from CT does not have to be linear with the current draw of the tool. You are not trying to measure the current, just detect flow/no flow. If you use a CT that produces max output with 1 amp and put it on a 10 amp tool, the CT will still reach max output and trigger the Arduino.

Could you use the noise from the tools to trigger the dust collector ? Then there would be no need for the Arduino to sense hazardous voltages.

Maybe there would be no need for an Arduino - just some op-amps and a relay, maybe a 555 timer.

...R

Robin2:
Could you use the noise from the tools to trigger the dust collector ? Then there would be no need for the Arduino to sense hazardous voltages.

Maybe there would be no need for an Arduino - just some op-amps and a relay, maybe a 555 timer.

...R

What type of 'noise' are you speaking of? How could you differentiate between the noise from the tools and the noise from the dust collector?

Making a timer that delays in multi-seconds (rather than milliseconds or tens of milliseconds) requires more than just a 555. I even gave up on that type of design and opted for an Arduino. I would have to guess the Arduino UNO has fewer chips than a component-based 10 second timer.

The band saw in particular is actually quieter than the collector itself.

I'm sure I could easily rewire the existing system to work with a CT, I may have to deal with the lights dimming when the collector cuts on but that can be fixed in the future.

I am still a bit confused about the output device. What is the reason a relay would not be the way to go? Motor contactors and soft start motor controllers seem to be several times more expensive than relays.

giser3546:
The band saw in particular is actually quieter than the collector itself.

I'm sure I could easily rewire the existing system to work with a CT, I may have to deal with the lights dimming when the collector cuts on but that can be fixed in the future.

I am still a bit confused about the output device. What is the reason a relay would not be the way to go? Motor contactors and soft start motor controllers seem to be several times more expensive than relays.

I'm sure the soft start controller are way more expensive. The contacts in a contactor are much more sturdy than those in a relay and are designed for the high current and high power loads of equipment and motors.

The differences:
A Relay:

  1. Goes Click when energized.
  2. Switches loads of lower wattage
  3. Applications include control circuitry
  4. Generally switch currents less than 5-10 Amperes.
  5. Generally switch voltages less than 120VAC
  6. Switch AC or DC
  7. Not normally rated in horsepower.
  8. Double throw is typical (normally open and normally closed contacts in one unit).
  9. Relay coils are AC or DC, but tend to be 5-24VDC with back emf power diodes to protect relay control electronics.
  10. The buck just gets passed here. Relays tend to be "pilot" control devices, controlling more powerful contactors.

A Contactor:

  1. Goes Clunk when energized.
  2. Switches loads of higher wattage
  3. Applications include power circuits (from electric motors to a country's main power grids).
  4. Generally switch currents above 10 Amperes.
  5. Generally switch voltages 120 VAC or greater.
  6. Switch AC or DC, resistive or inductive loads, but generally switch AC Loads.
  7. Usually includes a horsepower rating.
  8. Single throw is the norm (either normally open or normally closed contacts, rarely both).
  9. The buck stops here. Contactors are the real deal. They can be controlled by smaller, less powerful relays.

Appreciate it, Contactors don't seem to cost too much and look to be what I should go with. Since the overall tasking seems pretty simple would an arduino be overkill? Could I get away with something simpler?

It's all about time and effort. If you have played with microcontrollers before, the arduino is VERY easy to use. I don't know of anything that could be simpler or more flexible. As I mentioned, you could even add an ammeter option and display to it later on, for maybe $20. The system described needs a sensor, a timer, and a motor controller. Given the use of the CT for the sensor and a contactor for a motor controller, the only piece that has options is the timer. The arduino fits the bill for use as a timer. The problem will be deciding on how to implement the CT, which may require some work on the building wiring.

I am going to forego the CT and use a pushbutton, but I am also automating the blast gates so the dust collector on/off button and the gate open button are in the same switch plate.

Automating the blast gates sounds as interesting as it does complicated. If only for the sake of curiosity how do you plan on doing this?

adwsystems:
What type of 'noise' are you speaking of? How could you differentiate between the noise from the tools and the noise from the dust collector?.

It was just a suggestion. I assumed you would have a cheap microphone beside each machine you wanted to sense.

...R

Robin2:
It was just a suggestion. I assumed you would have a cheap microphone beside each machine you wanted to sense.

...R

Unfortunately most bandsaws don't make much audible noise, especially so when compared to a dust collector (super noisy). I was hoping you were going to say electrical noise, and I was very interested in hearing your thoughts.

adwsystems:
Unfortunately most bandsaws don't make much audible noise,

Sorry if I am flogging a dead horse ... I am just curious, and stubborn

I suspect if the microphone was very close to the noisiest part of the saw it would register different levels of noise when the saw is working and when it is not. A small wad of cloth might shield it from external noises.

...R

giser3546:
Automating the blast gates sounds as interesting as it does complicated. If only for the sake of curiosity how do you plan on doing this?

To make a long story short. Slow speed, higher torque reversible DC motors to move the gate linearly using a lead screw (length of threaded rod). Travel limited by limit switches (lever switches) with feedback from the normally open side of the limit switches. Power and direction will be controlled via small signal relays as the motors only draw 300-500mADC. Open-close commands are issued via pushbutton control panel. All of this to be run from an Arduino UNO.

Until I discovered and investigated the Arduino, I procrastinated on the project because of the time and effort it would take to wire an 8051. Since the Arduino is ready to go out of the box, it has jumped started this and a few other projects.

I thing I am of a different breed for 230volts and such.

you have a lot of choices for determining if they are on.
you can add a simple wall wart and connect it to the switch. when there is power to the motor, there is 4.5 volts out of the wall wart. (if you get a 4.5 volt one.)

as was mentioned, a CT or current transducer is a loop of wire that goes around ONE of the motor or switch wires, anywhere in the circuit, next to the breaker, next to the motor, anywhere. when there is power flowing, it otputs a voltage.
you can connect that to an AC/DC opto-coupler and then connect that to your arduino.

you can wire in a regular light, put it anywhere. light is on, machine is on. add a light sensitive resistor and you have another means to see when the machine is on. fails once the bulb burns out.

you could just as easily add a relay to each machine.
plug in the wall wart, when the machine is powered, the relay energizes, the power flows through the N/O contact and through the closed end switch. motor runs. once it hits the open end switch, the end switch interrupts power.
when the machine is turned off, the reverse. since each end switch interrupts power at the end of the stroke, you can easily control the motor.

many relays have two contacts Double Pole or DP, the second set could start the vacuum.
this is the old-school way.

giser3546:
The band saw in particular is actually quieter than the collector itself.

I'm sure I could easily rewire the existing system to work with a CT, I may have to deal with the lights dimming when the collector cuts on but that can be fixed in the future.

I am still a bit confused about the output device. What is the reason a relay would not be the way to go? Motor contactors and soft start motor controllers seem to be several times more expensive than relays.

best to google Current transformer, but the simple description is that any time ALTERNATING current is floowig on a SINGLE wire, there is a single magnetic field that is created. A CT interacts with that magnetic field and outputs a miniscule current, only enough to light a single LED, sometimes....
the CT has such little interaction and such little power draw that it is beyond the ability of most devices to know it is present.
however the CT can output a very high voltage. since voltage and current are inversely proportional in this device, the high voltage means low current. adding a resistor and an LED will use the current to light the led while giving the circuit of the CT a grounding effect (relative to itself) and keep the voltage low.
since it is non-contact, all you have to do is lift one wire, insert the CT over the wire, then re-connect the power wire.
some CT's are split core and can be snapped over the existing wire.
these are VERY simple and are beginner toys. very safe for the novice with just a few safety precautions.

I've been thinking about doing this for last couple years. Could a vibration sensor attached the tool be used as the trigger?