Blastgate
This project is a way of turning on the workshop's central dust collector by
means of a low voltage magnetic switch placed at each blast gate, and wired back
to a relay control box placed next to the dust collector. The magnetic switch
makes contact when the blast gate is opened. This sends a signal to the coil on
the relay which sends power to the dust collector. The magnetic switch is
powered by a 12vdc transformer in the main switch box. This is safe low voltage
power. The transformer gets its power from the main 120V line coming in to the
control box. The relay makes the high voltage connection from the 120V line
coming in to the control box through the relay and then to the outlet into which
the dust collector is plugged.
The advantage this system has over a wireless remote control system is that with
wireless you still must perform three acts to get started: 1) open the blast
gate, 2) press the remote to turn on the dust collector, and 3) turn on the tool
you want to use. With my magnetic switch system you have only two acts to
perform: 1) open the blast gate and 2) turn on the tool. There are no batteries
to replace and no remote to lose, to drop, to leave somewhere else and have to
go get (which is as easy as going over and turning on the dust collector in the
first place!), no being out of transmitter range, no false signals switching
your collector on or off. The magnetic switches are sealed in epoxy so there are
no open contacts which can get clogged with dust and fail. The magnetic switches
have about 1/2 inch of play. This means there is a lot of flexibility in placing
them on the blast gate. You can use hot melt glue to fasten the switches. There
are no holes to drill in the blast gate. I have built several units for
friends. One of these units has been in use for over five years. I do not have a
strong background in electronics. Some of you could build this with your eyes
closed, others would not have any idea where to start. I am happy to share my
information with anybody that asks. The parts for the main box run about $80 and
each magnetic switch costs $3.00. The only other supplies needed are 20 or 22
gauge bell or speaker wire and small wire nuts or tape. The system can be wired
to handle up to 20 amps 110 volt (1 1/2 hp).
One item of note, if one of the blast gate magnets or contacts comes loose and falls away from the other then your dust collector will turn on. I flip the breaker to the collector off when I am done for the day.
(click to enlarge)
I am working on assembly instructions, to be done soon.
Ok, Here's the deal. This set up works for me. I am not responsible for your actions. If you are not sure about this don't do it. If you know a lot more about this than I do, I'm always looking for ways to improve it, send me a note.
The pictures above show a 220 volt model I made. I have since found out that it is not as safe as I would like, therefore I do not recommend a 220v model. (for those that want to know why; first it should be a double breaker, and second the transformer I am using is a 110v model and should be a 220v model. I was pulling the 110v off of one leg of the 220v input.)
And the last straw is that a company has started selling one (cheaper)
