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electromagnet for tool dock

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  • undefined
    dc42 administrators
    last edited by 1 Sept 2021, 21:11

    @dutti the holding force of that magnet is 20N (about 2kgf) using a 2mm counter plate. Do you need that much force? If you don't, then you may find that a 24V electromagnet powered from 12V is sufficient.

    Duet WiFi hardware designer and firmware engineer
    Please do not ask me for Duet support via PM or email, use the forum
    http://www.escher3d.com, https://miscsolutions.wordpress.com

    undefined 1 Reply Last reply 1 Sept 2021, 22:09 Reply Quote 0
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      dutti @dc42
      last edited by dutti 9 Jan 2021, 22:10 1 Sept 2021, 22:09

      @dc42
      Yes it's should be 2kg 🙂 but if I really need them... I'm not sure, yet.
      I'll power them from the mainboard duet 3 or expansion board.
      I guess I can choose the voltage?
      What would be the best option to connect it? To the fan outputs?
      Richard

      undefined 1 Reply Last reply 2 Sept 2021, 11:11 Reply Quote 0
      • undefined
        dc42 administrators @dutti
        last edited by 2 Sept 2021, 11:11

        @dutti said in electromagnet for tool dock:

        What would be the best option to connect it? To the fan outputs?

        Yes.

        Duet WiFi hardware designer and firmware engineer
        Please do not ask me for Duet support via PM or email, use the forum
        http://www.escher3d.com, https://miscsolutions.wordpress.com

        undefined 1 Reply Last reply 7 Jan 2022, 06:14 Reply Quote 0
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          spirit.robotics @dc42
          last edited by 7 Jan 2022, 06:14

          @dc42 Hello, Im experimented a simmilar soluction for dock tool, Im planning use the Electromagnet with a low PWM frecuency to avoid heating, I have a doubt.

          In the post about connecting Fans said: "The polarity of the fans is important - don't connect them backwards." but the EM I have have the two cables blue without any polarity, only use 0.2 amps, so the pin could manage it, there is any risky to connect it to the FAN PWM pin? (in another post I wrote about my burned duet, maybe because of this)

          EM at 12V.jpg

          undefined 1 Reply Last reply 7 Jan 2022, 06:29 Reply Quote 0
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            rjenkinsgb @spirit.robotics
            last edited by 7 Jan 2022, 06:29

            @spirit-robotics
            You need to add a diode across the magnet coil to prevent back emf spikes damaging the Duet board.

            A "flywheel diode" function, in other words; preferably something like a 1A fast recovery or schottky rectifier diode.
            https://www.elprocus.com/freewheeling-or-flyback-diode-circuit-working-functions/

            The magnet coil polarity does not matter, but the diode polarity does - it should not be conducting with the normal supply polarity from the PSU or duet.

            Robert J.

            Printers: Overlord pro, Kossel XL+ with Duet 6HC and "Frankentron", TronXY X5SA Pro converted to E3D toolchange with Duet 6HC and 1LC toolboards.

            undefined 1 Reply Last reply 7 Jan 2022, 06:36 Reply Quote 0
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              spirit.robotics @rjenkinsgb
              last edited by 7 Jan 2022, 06:36

              @rjenkinsgb

              Thanks, now I know how I burned my duet, I was reading about it, you consider that this diode will work? it is rated 1amp

              569ab92c-89ce-4742-83b8-4ee5f34649d9-image.png

              undefined undefined 2 Replies Last reply 7 Jan 2022, 07:52 Reply Quote 0
              • undefined
                rjenkinsgb @spirit.robotics
                last edited by rjenkinsgb 1 Jul 2022, 07:53 7 Jan 2022, 07:52

                @spirit-robotics
                A 1N4007 is better than nothing, but not ideal - they are a basic rectifier and react quite slowly to changes in polarity (the "reverse recovery" time).

                As the purpose of the diode is to protect from fast spikes, a fast recovery or schottky diode is much better.

                A UF4007 (or other UF / UR 400x series) would be fine, likewise any 1A or higher schottky rectifier with a reasonable voltage rating.

                eg.
                https://www.amazon.com/Fielect-Rectifier-Rectified-Repetitive-Blocking/dp/B081YX4FZQ/ref=sr_1_12?crid=321AL9ZREAAET&keywords=UF4007&qid=1641541500&sprefix=uf4007%2Caps%2C132&sr=8-12

                https://www.amazon.com/BOJACK-Recovery-1A1000V-Electronic-Silicon/dp/B07Q4FNZZG/ref=sr_1_2?crid=2OEF4XRG1J1KB&keywords=FR107&qid=1641541663&sprefix=fr107%2Caps%2C135&sr=8-2

                Or use such as a 1N5819 or 1N5822 out of one of the cheap diode selection packs;
                https://www.amazon.com/MICSPSF-Assortment-Rectifier-Recovery-Switching/dp/B08VDH8H35/ref=sr_1_6?keywords=1N5819&qid=1641541799&s=industrial&sr=1-6

                Robert J.

                Printers: Overlord pro, Kossel XL+ with Duet 6HC and "Frankentron", TronXY X5SA Pro converted to E3D toolchange with Duet 6HC and 1LC toolboards.

                1 Reply Last reply Reply Quote 0
                • undefined
                  dc42 administrators @spirit.robotics
                  last edited by dc42 1 Jul 2022, 10:28 7 Jan 2022, 10:27

                  @spirit-robotics which Duet do you have, and if it is a Duet 2, what board revision?

                  All duets except older Duet WiFi/Ethernet boards have flyback diodes built in to the fan outputs, so external ones are not needed. Duet 3/3 Mini boards also have flyback diodes built in to all heater outputs except heater 0.

                  If you do need a flyback diode, then as @rjenkinsgb says a fast recovery or Schottky diode is preferred.

                  Duet WiFi hardware designer and firmware engineer
                  Please do not ask me for Duet support via PM or email, use the forum
                  http://www.escher3d.com, https://miscsolutions.wordpress.com

                  undefined undefined 3 Replies Last reply 7 Jan 2022, 10:41 Reply Quote 0
                  • undefined
                    rjenkinsgb @dc42
                    last edited by 7 Jan 2022, 10:41

                    @dc42 said in electromagnet for tool dock:

                    All duets except older Duet WiFi/Ethernet boards have flyback diodes built in to the fan outputs, so external ones are not needed.

                    That's fine, as long as the power to whatever is connected also comes from the same connector.

                    If by chance you use a separate positive supply and only switch the ground via the fan output, I'd consider an external flywheel diode to still be essential.

                    ps.
                    @dc42 - that rings a bell - another thread, someone having fan outputs fail, when using a separate positive feed?? I wonder if back EMF could be a cause?

                    Robert J.

                    Printers: Overlord pro, Kossel XL+ with Duet 6HC and "Frankentron", TronXY X5SA Pro converted to E3D toolchange with Duet 6HC and 1LC toolboards.

                    1 Reply Last reply Reply Quote 0
                    • undefined
                      rjenkinsgb
                      last edited by rjenkinsgb 1 Jul 2022, 10:46 7 Jan 2022, 10:45

                      Also, on a related subject -
                      having a flywheel diode (or snubber etc. depending on the load) close to the load itself means the flywheel current or voltage spike is not passed along the connecting wires through the machine, which reduces the chance of interference with other signals.

                      It's unrelated to damage to the electronics, but just good practice.

                      Robert J.

                      Printers: Overlord pro, Kossel XL+ with Duet 6HC and "Frankentron", TronXY X5SA Pro converted to E3D toolchange with Duet 6HC and 1LC toolboards.

                      undefined 1 Reply Last reply 7 Jan 2022, 17:09 Reply Quote 0
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                        rjenkinsgb @dc42
                        last edited by 7 Jan 2022, 11:06

                        @dc42
                        Thinking further on the external supply situation:
                        You may need to update the board info and tell users not to use external supplies at a higher voltage than the onboard output is set to, on outputs with flywheel diodes.

                        With a higher external supply to a load, the built-in flywheel diodes will presumably provide a direct path from that to the internal supply, when the output switch is off?

                        Robert J.

                        Printers: Overlord pro, Kossel XL+ with Duet 6HC and "Frankentron", TronXY X5SA Pro converted to E3D toolchange with Duet 6HC and 1LC toolboards.

                        1 Reply Last reply Reply Quote 0
                        • undefined
                          spirit.robotics @dc42
                          last edited by 7 Jan 2022, 16:59

                          @dc42 My Duet are the lasted version v 1.04.

                          Output M115:

                          RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.3 ELECTRONICS: Duet WiFi 1.02 or later FIRMWARE_DATE: 2021-06-15 21:45:03

                          About the diodes, they are always active? I supposed it is. In anycase how could be the circuit to put the diode? Thanks

                          undefined 1 Reply Last reply 7 Jan 2022, 17:04 Reply Quote 0
                          • undefined
                            dc42 administrators @spirit.robotics
                            last edited by 7 Jan 2022, 17:04

                            @spirit-robotics the diode will be active if the fan voltage select jumper is installed. As @rjenkinsgb says, the external solenoid supply voltage must be no higher than the selected voltage on the fan jumper (normally VIN).

                            Duet WiFi hardware designer and firmware engineer
                            Please do not ask me for Duet support via PM or email, use the forum
                            http://www.escher3d.com, https://miscsolutions.wordpress.com

                            1 Reply Last reply Reply Quote 0
                            • undefined
                              spirit.robotics @rjenkinsgb
                              last edited by 7 Jan 2022, 17:09

                              @rjenkinsgb Today I connect the board by USB and work fine, and connect a 5V FAN in the always ON fan and the fan work well.

                              However Im little worried if I try to connect the electromagnet, maybe the reason of the shortcut is different...

                              Just to understand, confirm ... in a board V1.04 I have the flyback diodes in place with the fans, so, in theory if I connect to the PWM Fan pin a small electromagent should be work?

                              The Electromagent, rated for 12V 0.2amps, but connected to the 5V pwn fan pin only need 0.09 amps ... could be work?

                              Electromagnet 12V.jpg
                              2022-01-07 (2).png

                              undefined 1 Reply Last reply 7 Jan 2022, 17:24 Reply Quote 0
                              • undefined
                                dc42 administrators @spirit.robotics
                                last edited by dc42 1 Jul 2022, 17:24 7 Jan 2022, 17:24

                                @spirit-robotics what position is the fan voltage section jumper in?

                                And what VIN voltage are you using?

                                Duet WiFi hardware designer and firmware engineer
                                Please do not ask me for Duet support via PM or email, use the forum
                                http://www.escher3d.com, https://miscsolutions.wordpress.com

                                undefined 1 Reply Last reply 7 Jan 2022, 17:44 Reply Quote 0
                                • undefined
                                  spirit.robotics @dc42
                                  last edited by 7 Jan 2022, 17:44

                                  @dc42 this is a test from my power supply, just to check.

                                  I want to connect the electromagnet to a pwm fan pins at 5V, from the reading I understand that it will work because the board have the flyback diode and the current is small.

                                  My idea is hold with the electromagnet my tool, I already tested the electromagnet with the DC power supply and the current is only 0.09 ampers, but still have enough force to hold the tool without getting hot the electromagnet.

                                  Please let me know your recommendations.

                                  ? undefined 3 Replies Last reply 7 Jan 2022, 18:49 Reply Quote 0
                                  • ?
                                    A Former User @spirit.robotics
                                    last edited by A Former User 1 Jul 2022, 18:52 7 Jan 2022, 18:49

                                    This post is deleted!
                                    1 Reply Last reply Reply Quote 0
                                    • ?
                                      A Former User @spirit.robotics
                                      last edited by 7 Jan 2022, 18:55

                                      @spirit-robotics
                                      Hi again
                                      My solution is still working good. It's quiet simple.
                                      I could share my solution...

                                      Cheers
                                      Richard

                                      undefined 1 Reply Last reply 8 Jan 2022, 04:14 Reply Quote 0
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                                        spirit.robotics @A Former User
                                        last edited by 8 Jan 2022, 04:14

                                        @gruna-studio Thanks, sure if you like, I already have my design, I want to hold a small iron plate attached to the tool with the electromagnet, no moving parts.

                                        Im only double check how operate the electromagnet without burn again my board.

                                        Best

                                        1 Reply Last reply Reply Quote 0
                                        • undefined
                                          spirit.robotics @spirit.robotics
                                          last edited by 9 Jan 2022, 15:22

                                          @spirit-robotics Hi dc42, please let me know your comments. Best

                                          undefined 1 Reply Last reply 10 Jan 2022, 20:27 Reply Quote 0
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