I found cheap, simple current sense switches for dust collector

[Lynn Kasdorf]

I am installing a dust collector for my miter saw, and for the heck of it, I did a search to see how cheap current sensing switches have gotten. Well, it turns out, they have gotten cheap!

There are several out there- but here is one:

https://blackhawksupply.com/products...fDsaAlrQ8P8HAQ

You run one leg of the power to your saw through the hole, and you get a normally open set of contacts that close when current is flowing. Use those contacts to switch power to a relay that controls your dust collector, and bada-bing, you have an automatic dust collector!

Google "current sensing switch" and you'll find a lot of relatively cheap products. Yes, you can get down to the circuit level and build your own, but for an industrial quality control for $15, plus a relay (I have several laying around), I'll go that route.

FYI

[Chris Padilla]

Hmmmm, looks pretty nice and I like the price!

[Jim Becker]

Very nice way to control the control-side of a contactor for this application!

[Malcolm McLeod]

Good solution.

I'd recommend an 'off-delay' relay paired with it (so the DC runs for a few seconds after the saw shuts off). The variable time relays are also worth a look as well. I have an i-socket (4s. delay off) on my CMS, and wish it would run longer for repetitive cuts. The vacuum dies just as I get lined up for the next cut, and while cycling the CMS on/off is probably unavoidable, there is no reason to do the same to the connected shopvac.

The inrush current and wear and tear on the motor is worse than letting it run for an extra 10-12 seconds.

[Ben Rivel]

Nice, just grabbed one off eBay for $15 shipped. Might be fun to play around with. I already have iSockets and a couple wireless remotes for my large DC, but this might be used to someday create a system to automate my blastgates.

[Lynn Kasdorf]

Good solution.

I'd recommend an 'off-delay' relay paired with it (so the DC runs for a few seconds after the saw shuts off). The variable time relays are also worth a look as well. I have an i-socket (4s. delay off) on my CMS, and wish it would run longer for repetitive cuts. The vacuum dies just as I get lined up for the next cut, and while cycling the CMS on/off is probably unavoidable, there is no reason to do the same to the connected shopvac.

The inrush current and wear and tear on the motor is worse than letting it run for an extra 10-12 seconds.

Good point. If I build an arduino controller, this would be easy, but I'll look for such a relay as you describe. Heck I probably have on in my vast stores of junk.

[Lynn Kasdorf]

And note that there are several mfrs of this sort of thing, so do some googleing. Dwyer is another I found.

[Ben Rivel]

And note that there are several mfrs of this sort of thing, so do some googleing. Dwyer is another I found.

Dwyer makes one? Any idea what the part number is?

[Lynn Kasdorf]

Dwyer makes one? Any idea what the part number is?

http://www.dwyer-inst.com/Product/Pr...ches/SeriesCCS

You'll have to research or call them to get the best part number for your app. I'm sure they have application engineers eager to help.

[Ben Rivel]

http://www.dwyer-inst.com/Product/Pr...ches/SeriesCCS

You'll have to research or call them to get the best part number for your app. I'm sure they have application engineers eager to help.

Nice, looks like the

CCS-121050 is about the same price and specs as the ACI

A/MCS. Good to know.

[Mike Heidrick]

Do an ebay search on sct-013-000 non-invasive AC Current Sensor Split core Current transformer. They are about $5 delivered. They can also easily be placed around wires you already have run with plugs on them. There are other models there for $5-$6 as well.

[Chris Padilla]

Do an ebay search on sct-013-000 non-invasive AC Current Sensor Split core Current transformer. They are about $5 delivered. They can also easily be placed around wires you already have run with plugs on them. There are other models there for $5-$6 as well.

Wow, those are about a dime a dozen there!

[John K Jordan]

I went a different route which works for me. I use a remote wireless RF transmitter/receiver to control the 220v DC contactor (relay) and put keyfob size remote transmitters at each major tool. This way I turn the 5hp DC on and off on my timing. Since I understand cycling a large motor too quickly can cause overheating, I generally turn it on then leave it on until I'm ready to walk away, even if I turn the saw on and off many times. Fortunately, my DC is in a sound insulated closet so my nerves and sanity don't suffer.

In addition, I sometimes use a shop vac hose connected to a blast gate to clean up stray dust that escaped from the bandsaw or the unavoidable mess around the lathe. For this I keep the DC running for a while after I turn the machine off.

Some people clip a little wireless transmitter to their belt or pocket but I'm too scatterbrained to remember to do that each time.

I've been using one for about 3 years. I wired it into a box along with the bin-full sensor electronics and alarm and mounted it in my main shop along with a controller cutoff switch:

DC_controller_box_ce.jpg DC_electrical_shop_s.jpg

I can't find the exact model I ordered but this one on Amazon looks close: https://www.amazon.com/gp/product/B000BQRHMM

JKJ

[Alan Schaffter]

Some of you may remember the automatic dust collection set-up that I built and have been using for many, many years. It uses current sensor switches by CR Magnetics at each power outlet that supplies a machine. The current sensor switches operate low voltage/low current (24V/60 mA) SMC electric solenoid air valves that port shop air to pneumatic cylinders which open and close my blast gates. A separate sensor on the transformer that provides the 24V to the solenoids, controls the 220V contactor which powers my DC. (to keep the DC motor from cycling too often, while each gate opens and closes when machine power is cycled, the DC stays running until I manually shut it down.)

Please check the ratings of any current sensor switch and the demands of the application. The solid state switches in many of these units are not rated to operate anything but small, low voltage/low current devices (like my solenoid valves) directly- NOT higher voltage/current items like a shopvac, DC, etc. For those you will need an intermediate relay/contactor, PLC, Arduino, etc. Also, some of these current sensor switches come in NPN or PNP configurations so they must be wired accordingly.

Also, some (most?) of these units will only work with one conductor. If you try to clamp it around a power cable containing both hot and neutral wires, the currents will cancel flow in the torriod and the current sensor switch will not operate.

Here is the switch rating of the unit in Lynn's post taken from the spec sheet: "A/MCS: 0.5A Continuous, 36 VAC/VDC"

For the Dwyer unit: "For fixed set point models: 0.3 A @ 135 VAC/DC; For adjustable set point models: 1 A @ 240 VAC."

Many of the SCT models on eBay are only rated for only 30 - 50 mA (milliamps).

[Curt Harms]

I don't know if my problem would occur with one of the 'donut' current sensors but I have a mid '90 Fein vac with machine activated plug. I also have a Delta 12" CMS with dual lasers. The lasers are switched but the laser power supply is not. The power supply draws enough current with the lasers turned off that the Fein vac will not turn off. It doesn't turn on without the saw being started but it may or may not turn off. As long as the sensor can be set or if the 'on' amperage is high enough it wouldn't be an issue.