I have seen gadgets that sense the current flow in a circuit when the chop
saw is turned on, and it then turns on a plug that the dust collector is
What I want is some type of plans for a home brewed one. I have a variety
of relays and magnetic contactors to work from.
Anyone know of some plans, or smart enough to draw something I can build?
I've made several of these. The first one I made using a small current
transformer (CT) from Functional Devices. I had to use it to power a relay
that turned on a small power transformer to turn on a larger relay to turn
on the vac. Clunky but functional.
The next one I made used another relay in a box (RIB) from Functional
Devices. This one had a CT on board. I experimented with the size of a
dropping resistor connected from the CT to the load circuit to get it to
work. The resistor had to be subbed each time you changed to a different
vac. Again not elegant but functional.
A year ago, the FD people offered a relay with a CT and an adjustable time
delay off load relay. P/N RIBD01BDC-DOB.
This thing is the cat's meow.
All you have to do is connect the box to a regular 4 square with a split
duplex outlet, one for the saw, one for the vac. I got fancy and used a
panel mounted recessed plug for the line connection, although you could
substitute a cheater cord.
I think when I got done I spent about $75, but the relays are 10 amp motor
duty and it's rugged and portable - a requirement for all the left feet in
If you're interested in a schematic, let me know. I'll hold my beer in one
hand and draw one up for you on the back of the napkin.
I think I have enough of a clue to build one with the junk I have on hand
now. The problem with the one like Sears is that if the unit all runs off
of one circuit, there is not enough capacity to run two 13 amp units. I'll
fix that in my design.
Is the supply circuit going to handle 2-13amp units? Unless you
configure in a delay, which most of these units have built in you might
be popping a breaker every time you start the saw.
For instance, my Festool vac turns on a second or two after starting the
power tool. The power tool plugs directly into the vac for power. I
don't recall the amps that the vac pulls but it is suggested that the
suction be turned down when running larger power tools to decrease the
chance of blowing a breaker. And IIRC the vac and power tools are soft
start to cut down on the surge.
Maybe he likes building electronic stuff for himself the way we like
doing woodworking for ourselves.
I can't remember building anything for myself that was cheaper than if
I'd bought one. Sure, mine might be more durable and solid, but not
Yep, I like to dabble in all things. But mine will be virtually free, if it
come out like I think. You see, I have been organizing my work area, and I
have more stuff than I ever dreamed. I made boxes to store stuff, just to
organize and to par down my excess wood supply. I have to reduce the
By the way, anyone have need for a Velux skylight, from the early 90's with
flashing kit, that has never been installed? Good condition, in box. It
has to go. Size is about 4 foot by 4 foot. West Central NC area. Will
ship if you pay shipping.
I counted it up. I have a wall of storage boxes, about 7" x 8 1/2" x 13".
Some are double and triple wide, but if they were all singles, I would have
225 boxes. They are filled with either tools of any type you can imagine,
or supplies of any description and quantity. Then there are about 10 boxes
that are about 50% larger. Then there are two sets of shelves 2 foot x 8
foot and about 6 foot tall, and one set about 1 x 8 x 12. Two rolling tool
chests. That does not count wood storage.
I'll post some pictures a few months down the line when I get it somewhat
close to like I want it.
So, I think I have everything I need to make a dust collector automatic
switch work, free. I am going to start with trying to make my own
transformer/current sensor. I have some old ones I can rewind to handle the
amps. Next in line, a bridge rectifier, which I think I have the parts for,
which the output will go to a big transistor left over from my dad's days of
fixing his own tv's. The switched output from that will close the switch to
let 24 volts from a power supply energize the hold in winding for a magnetic
starter, to turn on the dust collector. I will experiment with some
capacitors and resistors to keep the transistor energized after the current
is gone, to give it a time delay, so the collector is not starting and
stopping all of the time. I will shoot for 20 to 30 seconds. If that does
not work, I think I can hack an outdoor motion detector timing circuit to
get the desired time delay. The auto switch will also have two current
sensors, one for 110 and one for 220.
I need to rewire the shop, since I have drop cords running everywhere for
machines. I plan to run a two circuit 20 amp 110 line, one leg fed through
the auto switch, and one leg not. At each machine station, I will place a
switch, to feed the outlet from the sensor circuit or the non auto run
circuit. That way I can decide if I want to be starting the dust collector
all of the time. All of the 110 stuff will go on the same lines. It is
just me, so there really is no need to be able to run more than one machine
at once. The 220 equipment I have is just the table saw and air compressor,
so those will be separate, with just the table saw on the auto option.
There will of course be various other lighting and receptacle branches for
other stuff through out the work area, along with ventilation exhaust fan,
and air filter, and entertainment (tv and stereo and computer) stuff.
The you tube video that Leon, or someone posted on the guy making a switch
for his dad got me going. Thanks for that, whoever that was. I only have a
shop vac and a dust collector I made from an old barrel and an electric leaf
blower, but it is too small. I may use it for a boost somewhere, if I need
it, or just as a vac. I am going to make a dust collector along the lines
of the one I saw on you tube, which was made from an old portable table saw.
I have one of those, at 10 amps, but am going to use a chop saw motor I have
that got run over by a Lowes truck that is larger at 13 amps. I only need
to find a drum that will stand the vacuum, to be able to build it.
Big plans, huh? It will take a while to do it all, but I only have time on
my hands, being disabled. I work for an hour and lie down for close to an
hour. Like eating an elephant, it will all get gone, one small bite at a
Just use a double pole switch for the saw, and have the second side
control power to the transformer that supplies power for the
If your saw uses a contactor, get a "pilot contact" for the contactor
and have it switch the low voltage to the DC contactor, or connect a
transformer to the switched side of the contactor to supply the low
voltage for the DC contactor.
Or build a circuit that "hears" the saw run and turns on the dust
Lots of ways to skin this particular cat.
Oh, that is the reason I did not like what I had seen for sale. It would
not, I think. The dust collector will be pushing 13 amps and the chop saw
also 13 amps. Now way even a 20 amp circuit could hold that.
My design will have 2 power inputs, most likely 20 amps on each one, and I
will make sure that both are fed from dedicated breakers on the same side of
neutral so there will be no possibility of coming across 220 inside the box.
With that going on, I will not worry about starting the saw and the DC at
the same time.
Yep, but I think I'll go with my way. Too much noise in a shop too spread
out for an audio switch. None of my stuff has contactors. Too much
equipment or not practical to put two pole switches in everything.
I plan on starting the dust collector on auto (or at least will be able to
choose to) for a shaper, router table, lathe, jointer, plainer, radial arm,
chop saw, sanding table, stationary belt/disc sander and table saw. All
will be sensed when they are run because they will all be on the same line,
which the auto switch will be on, except for the table saw (being on 220)
will have its own current sensor in the switch.
That's ok if you have current sensors. But simply wiring a low
voltage transformer across the motor leads and connecting the output
to the relay operating the dust collector is a whole lot simpler - - -
any machine running supplies energizing current to the relay, and on
goes the dust collector .
For the 220 table saw you just need a transformer with a 220 primary.
I've got a good handfull of old bell transformers, thermostat
transformers, 12 volt wall warts, and power transformers out of all
kinds of transistorized stuff - bet you do too. Keep it as simple as
possible, but no simpler - - -
True, but If I am using one machine and cutting, then fitting, I would
rather the DC not run the entire time I don't need it, and I sure don't want
to repeatedly close and open gates to turn it on and off.
Much better to me to open the gate I need and leave it open until I don't
need it, and let the switch auto on and off when it is needed.
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