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electronic control of my swing arm drilling and tapping machine.

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  • electronic control of my swing arm drilling and tapping machine.

    The swing arm drill I built has three 24vdc valves. One valve is the directional control valve that controls the double acting cylinder to raise and lower the arm. The other directional control valve runs the hydraulic motor for the drill head. Now comes the tricky part. The two mentioned valves sit on a manifold. They are closed center valves. The manifold has pressure in and a return to tank line. In order for the control valves to have pressure another valve is used to shut off the flow to tank thereby forces the pressure to go to the directional control valves. So for any function to work two solenoids have to be actuated. The shut off valve and one solenoid to open the flow to the motor or to the height adjusting cylinder. So in total there are five solenoids to be actuated. Now the problem. I know how to do the control using a PLC. Using function block diagram programming it is easy. But how would one build the circuit without a PLC? I use push buttons to activate the solenoids for the directional control valves. I would have to build something with four relays going to the shut off valve so the 24volts don't feed back to the other solenoids on the DCV's.

    Or is there an easier way to accomplish this circuit?
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    Use diodes in strategic spots to stop the back feed.

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    • #3
      Pre Plc the standard way was with contractors, hard wired, the mte contractors were popular as the contacts could be set NO or NC with just a screwdriver, relay logic though antiquated still can be made to do the job, but difficult as hell to fathom!
      I'd stick with a Plc as you've got to grips with it, could spice it up with a HCI panel if you want some extra things to tinker with,
      Mark
      (S5 made me very sad!)

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      • #4
        Thinking about this more-

        Ran into this on a similar dc solenoid hydraulic valve project a few years ago. As I recall, I used a diode on the ground side of each solenoid.

        On edit:Above is wrong. Here is what I REALLY did:

        Hot wire from each switch runs to a directional valve solenoid, then through a diode to the block off valve solenoid. Repeat for each directional valve.

        Thus any energized directional valve also energizes the block off valve but diodes dis allow back feeding of the wrong directional valves.

        In my case I needed to fire an electric/hydraulic power unit when valves where energized rather than a block off valve, but the principle is the same.
        Last edited by SVS; 04-19-2016, 01:02 AM. Reason: Bad/Slow memory

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        • #5
          Originally posted by SVS View Post
          Thinking about this more-

          Ran into this on a similar dc solenoid hydraulic valve project a few years ago. As I recall, I used a diode on the ground side of each solenoid.

          On edit:Above is wrong. Here is what I REALLY did:

          Hot wire from each switch runs to a directional valve solenoid, then through a diode to the block off valve solenoid. Repeat for each directional valve.

          Thus any energized directional valve also energizes the block off valve but diodes dis allow back feeding of the wrong directional valves.

          In my case I needed to fire an electric/hydraulic power unit when valves where energized rather than a block off valve, but the principle is the same.
          What diode would I use to accomplish this task?
          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

          Comment


          • #6
            The diode would depend on the current rating of the solenoids. The standard rectifying diode up to 1A used to be the 1N4007, they cost about 6 cents each :-)
            For up to 3A, get a 1N5408 for two cents more!

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            • #7
              Originally posted by ikdor View Post
              The diode would depend on the current rating of the solenoids. The standard rectifying diode up to 1A used to be the 1N4007, they cost about 6 cents each :-)
              For up to 3A, get a 1N5408 for two cents more!
              What, I ain't throwing money away on a larger diode if I don't need it. Man O Man some people just like throwing money away.

              The solenoids use less than one amp of current. I looked online to find diodes. Did you know that there are a lot of different diodes out there!!!! Especially for the Electrically challenged like me it is a daunting task this electronic stuff.
              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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              • #8
                OK there are even more than a lot of different kinds of diodes. There is a sh!t load of diodes. A oil tanker full of different kinds of diodes. The universe is full of different diodes.

                Any of these work?
                https://www.google.de/search?q=1N540...diode&tbm=shop
                How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                • #9
                  If the coils are AC you use 4 double pole relays, one for each move and wire one of the contacts of each relay in parallel to power the bypass valve. The other contact would power your "work" valve. Any valve operation ensures the operation of the bypass valve this way. No PLC needed.
                  Helder Ferreira
                  Setubal, Portugal

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                  • #10
                    Originally posted by Noitoen View Post
                    If the coils are AC you use 4 double pole relays, one for each move and wire one of the contacts of each relay in parallel to power the bypass valve. The other contact would power your "work" valve. Any valve operation ensures the operation of the bypass valve this way. No PLC needed.
                    The solenoids on each valve are 24vdc.
                    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                    • #11
                      Can still use the relays. In this way you save the control switch from the inductive load. The diode solution is also viable. 4 diodes pointing to the bypass valve from each of the others. Powering any of these also powers the bypass.
                      Helder Ferreira
                      Setubal, Portugal

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                      • #12
                        Use an Arduino, they like PLCs but cheap, kids use them, some only cost $5
                        My neighbours diary says I have boundary issues

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                        • #13
                          Originally posted by Black Forest View Post
                          OK there are even more than a lot of different kinds of diodes. There is a sh!t load of diodes. A oil tanker full of different kinds of diodes. The universe is full of different diodes.

                          Any of these work?
                          https://www.google.de/search?q=1N540...diode&tbm=shop
                          Well ain't electronics fun :-)
                          All of the diodes in your search are fine as long as they have the same part number. You could create a business account at http://de.farnell.com/ and you'd pay only the 8 cents and no shipping.....

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                          • #14
                            Re diodes-I used some from the parts store intended for vehicle charging/ignition system.

                            Factory made pigtail six inches long with diode soldered in the middle and heat shrink wrapper.

                            A quick google gave me useless fluff.

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                            • #15
                              Ok, checked into this further.

                              Used Radio shack 276-1141, probably no longer available, but comparable to the 1N5408 mentioned above but already set into a pigtail with heat shrink.

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