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  • contactor control wiring question

    please tell me what's wrong with this application.

    i would like this contactor to activate whenever a 220v power tool is activated:

    Packard C240A 2 Pole 40 Amp Contactor 24 Volt Coil Contactor: Amazon.com: Industrial & Scientific

    but i want to activate the contactor via this current sensing (CS) switch:

    Relays / Switches - CR Magnetics

    specifically, the CR9321 shown on the linked page.

    the 220v circuit supplying power to a dedicated power tool outlet will be configured so that one leg of the 220 circuit will pass through the CS switch's sensing "donut". when the power tool is activated, and current passes through the 220v conductors, since one of the conductors passes through the CS switch, the CS will close. i'm planning on putting a 24v transformer between the contactor and the CS switch. that way, when i activate a 220v power tool, the circuit to which the tool is connected will experience current flow, the CS switch will close and complete the control circuit of the contactor. the CS switch's control leads are wired between the 24v transformer and the contactor's control connections. if this works as i'd like it to, the contactor will then close and activate whatever is connected to the contactor's line voltage connections.

    anyone out there famliar with low voltage controls who can look at what i'm trying to do and provide some insights regarding what i've overlooked or misunderstood? constructive comments appreciated.
    there's a solution to every problem.....you just have to be willing to find it.

  • #2
    Re: contactor control wiring question

    How are you going to get your current flow if you are breaking one leg where your sensor is going? I would like to see a drawing to help further simplify your post...for my sake.
    AllurePlumbing.com
    • leak detection
    • drain cleaning
    • utility locating
    • conductor fault locating
    • and other specialties.

    Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

    Comment


    • #3
      Re: contactor control wiring question

      the current carrying leg goes through a hole in the current sensing switch. this creates a magnetic field in the sensing switch which causes an internal switch ( i'm suppposing somewhting tranistorized, although i don't know that for sure) to close. since 24v will get the contactor control circuit to close, my thought is to interrupt that action with the current sensing switch so that when the tool attached to the dedicated circuit is energized, current flow will cause the CS switch to close, completing the low voltage circuit causing the contactor to close therely energizing whatever the line voltage side of the contactor is connecrted to. look at a picture of the linked CS switch for how the line voltage goes through a part of that CS switch.
      there's a solution to every problem.....you just have to be willing to find it.

      Comment


      • #4
        Re: contactor control wiring question

        Share with us what kind of diabolical device you are building

        Im sure Honeywell makes an all-in-one relay you are looking for.

        Comment


        • #5
          Re: contactor control wiring question

          Ahhh, somehow misread. Sounds like you are good to go. Check these guys out.
          AllurePlumbing.com
          • leak detection
          • drain cleaning
          • utility locating
          • conductor fault locating
          • and other specialties.

          Greensboro NC, Winston-Salem NC, High Point NC, Thomasville NC, Kernersville NC

          Comment


          • #6
            Re: contactor control wiring question

            For what you are describing you will want the CR 9321 ACA
            You will need to add the suggested capacitor/resistor snubber in order for it to reliably turn off.
            http://www.crmagnetics.com/Products/...tPDFs/9321.pdf

            Comment


            • #7
              Re: contactor control wiring question

              wbrooks...if i'm planning on using low voltage (24v) to activate the contactor, why suggest the 9321 aca? isn't that for alternating current (line voltage)? i came across this schematic done by another woodworker who uses the 9321 (pnp) to activate a 24v solenoid. wouldn't i just use the same components as those shown in the "schematic", but substitute the contactor i linked in the opening post for the solenoid in the "schematic"?
              Attached Files
              there's a solution to every problem.....you just have to be willing to find it.

              Comment


              • #8
                Re: contactor control wiring question

                Originally posted by bhead62 View Post
                Share with us what kind of diabolical device you are building

                Im sure Honeywell makes an all-in-one relay you are looking for.
                i'm trying to activate this switch:

                MBright Tools IVAC Inc.

                which is for 110v tools, with a 220v table saw. the current sensor will sense when the 220v dedicated outlet is sending power to the table saw. the current sensor will close, completing the low voltage circuit shown in the previouisly posted "schematic" and close a contactor (relay). when the relay closes, it will turn on a 40w bulb, the power for which comes from the tool outlet of the ivac switch. the slave outlet of the ivac will sense the .25A load of the light bulb and activate the slave tool, which is my 220v, 1.5hp dust collector. it's a little rube goldberg, but not having to concern myself abotu activating or deactivating the dust collection tools makes for a safer environment.

                obviouisly, just converting everything to ivac pro switches would be simpler and easier but much more expensive. besides, i've got it to where my two ivac switches are daisy chained to activate the dust collector and a shop vac (which will eventually handle blade guard dust collection duties for the table saws) simultaneously. also comes in very handy for the radial arm saw, my routert table and, eventually, all 3 table saws (albeit one at a time).
                Attached Files
                there's a solution to every problem.....you just have to be willing to find it.

                Comment


                • #9
                  Re: contactor control wiring question

                  Simpler circuit.
                  The ACA can be used from 24 to 240 VAC and will sink 1 amp which should be enough to power the coil on the relay.
                  Check if it is an AC relay as well if not you will still need to rectify to stop the relay from buzzing but you will have more drive power
                  The PNP needs a bridge and can only sink 120 mA which may not be enough to drive the relay.
                  If this is tested then go for it but if not I would check the requirements for the coil on the 240V relay

                  Comment


                  • #10
                    Re: contactor control wiring question

                    Simpler circuit, put a double gang switch on your saw (or on the wall) that will turn on both the saw and dust collection system.

                    Comment


                    • #11
                      Re: contactor control wiring question

                      Originally posted by johncameron View Post
                      Simpler circuit, put a double gang switch on your saw (or on the wall) that will turn on both the saw and dust collection system.
                      considered and dismissed. i want to activate one switch on the power tool and have the slave tools come on and off relative to the operating state of the activating power tool. my unisaw has a magnetic starter switch with a 24v power on circuit. i don;t think a double gang switch address that situation? it might for the band saw, but that would mean changing out power switches if i didn't want to mount somehting on a wall.
                      there's a solution to every problem.....you just have to be willing to find it.

                      Comment


                      • #12
                        Re: contactor control wiring question

                        Originally posted by wbrooks View Post
                        Simpler circuit.
                        The ACA can be used from 24 to 240 VAC and will sink 1 amp which should be enough to power the coil on the relay.
                        Check if it is an AC relay as well if not you will still need to rectify to stop the relay from buzzing but you will have more drive power
                        The PNP needs a bridge and can only sink 120 mA which may not be enough to drive the relay.
                        If this is tested then go for it but if not I would check the requirements for the coil on the 240V relay
                        thanks for the reply, but it's a little "jargonesque" in it;s tone. do you think you could dumb it down a bit for me in terms of the handwritten schematic included in posting #7?
                        there's a solution to every problem.....you just have to be willing to find it.

                        Comment


                        • #13
                          Re: contactor control wiring question

                          Originally posted by FINER9998 View Post
                          considered and dismissed. i want to activate one switch on the power tool and have the slave tools come on and off relative to the operating state of the activating power tool. my unisaw has a magnetic starter switch with a 24v power on circuit. i don;t think a double gang switch address that situation? it might for the band saw, but that would mean changing out power switches if i didn't want to mount somehting on a wall.
                          I dont follow. I thought you wanted your dust col sys come on whenever you turn on one of your saws. You just run one at a time, right?

                          It could be done with switches but you would have to hard wire it to your band and table saw. the switch could be switching 24v for that matter.

                          If you still want to do the sensing switch thing, why not just have the relay in the sensing switch drive the contactor coil, and that feeds your dust collection system? It could be problematic if the sensing switch has a narow pick-up range. You dont want to be fiddling with sensitivity adjustments all the time.

                          As wbrooks said it can be done electronicly but it must be designed based on the specs of the contactor coil. Personally, I would not trust the electronic circuit unless it underwent some serious testing.

                          Comment


                          • #14
                            Re: contactor control wiring question

                            i am copying the control wiring for this pretty sophisticated dust collection system:

                            Watch "Automatic Dust Collection" Video at American Woodworker

                            alan is the architect of the hand written scematic i posted in post #7, so i'm fairly confident it works.

                            i should also mention that i can connect any of my power tools to my ivac switch set up and have automatic dust collection activation for any tool. employing switches that are specific to only one tool defeats that functionality. the issue, as you note in your third paragraph, is ensuring that the current sensing switch will activate the contactor ( the coil rating for the contactor has to be less than the rating of the current sensor switch). now that i've confirmed that the contactor needs 37mA for activation, and the specified current sensor switch provides up to 120mA, i am really confident i can replace the solenoid in the schematic with a 24v, 2pole 40A contactor and it will be activated by the current sensor switch. BTW, the contactor isn't activating the power tool. the contactor is only activating a 40W bulb (why a 40A, 2pole switch for a light bulb? because i can get it for ~$6, it'll do what i need it to do re: the light bulb and it can be repurposed it in the future should my needs change) to initiate the powering up activity of the lead ivac switch. but if i configure this correctly, i will have created a method where all the 110v stationary tools will activate the DC tools automatically, and any 220v tools will do the same.
                            there's a solution to every problem.....you just have to be willing to find it.

                            Comment


                            • #15
                              Re: contactor control wiring question

                              Prety cool system. It looks like he had the automation just for the shoots, and a start/stop is on each machine for the dust col motor.

                              Yes, The current switch should activate the contactor ok, I was trying to say the different machines will draw varying amperage and could be problematic if the current switch will not turn on and off like you want.

                              BTW, The 37ma spec sounds way low to me. (unless this is one tiny contactor) That might be a holding current of the coil, but will likely draw much more during in-rush current. Use mov's across the coil (ac) or diodes/snubbers (if dc) to save the rest of the circuit from spikes when the coil de-energizes.

                              Good luck.

                              PS: I will stick with turning my Dust col system by hand for now.

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