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Re: [Electronics_101] Open Antenna becames Quiet Relay

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  • Stefan Trethan
    ... what do you mean, like soundwaves? i thought you speak of noise on the signal? ST
    Message 1 of 16 , Nov 3, 2004
      On Wed, 3 Nov 2004 12:19:14 +0100, Vito Russo <vrusso@...> wrote:

      > An explanation. I'm speaking of ACOUSTIC noise.
      >
      > Vito

      what do you mean, like soundwaves?
      i thought you speak of noise on the signal?

      ST
    • Vito Russo
      I ve understood too late that there could be a misunderstanding using only noise .. Yes, I m speaking of soundwaves. The demo equipment should be placed in a
      Message 2 of 16 , Nov 3, 2004
        I've understood too late that there could be a misunderstanding using only
        "noise"..
        Yes, I'm speaking of soundwaves.
        The demo equipment should be placed in a library, so it's not acceptable to
        hear a continous TIC TAC..

        Vito

        ----- Original Message -----
        From: "Stefan Trethan" <stefan_trethan@...>
        To: <Electronics_101@yahoogroups.com>
        Sent: Wednesday, November 03, 2004 12:20 PM
        Subject: Re: [Electronics_101] Open Antenna becames Quiet Relay


        >
        > On Wed, 3 Nov 2004 12:19:14 +0100, Vito Russo <vrusso@...> wrote:
        >
        > > An explanation. I'm speaking of ACOUSTIC noise.
        > >
        > > Vito
        >
        > what do you mean, like soundwaves?
        > i thought you speak of noise on the signal?
        >
        > ST
        >
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        > Yahoo! Groups Links
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      • Stefan Trethan
        ... so the problem is the switching noise of the relay? get the most silent one you can find and put it in a noise box. efficient noise blocking requires
        Message 3 of 16 , Nov 3, 2004
          On Wed, 3 Nov 2004 12:40:08 +0100, Vito Russo <vrusso@...> wrote:

          >
          > I've understood too late that there could be a misunderstanding using
          > only
          > "noise"..
          > Yes, I'm speaking of soundwaves.
          > The demo equipment should be placed in a library, so it's not acceptable
          > to
          > hear a continous TIC TAC..
          >
          > Vito

          so the problem is the switching noise of the relay?

          get the most silent one you can find and put it in a noise box.
          efficient noise blocking requires layers of acoustic very dense and very
          light materials.
          e.g. cushion the relay with foam, put it in a steel box made of 5mm steel
          plate. cushion this
          box with another layer of foam. should be totally silent.

          the secret to kill noise to dampen the mechanic oscillation (noise through
          solids) by using
          a high impedance conductor (foam) and feed it into a lot of weight. it is
          not able to drive the
          weight. The second secret is to prevent sound waves through air. enclosing
          in foam.

          If you don't want to use steel to make box i found that small sandbags
          (plastc kitchen bags filled with sand) work very well. just wrap it in
          alternating layers of sand and foam.

          But keep in mind the number of switching cycles of a relay is limited, so
          continuous click-clack is no good.

          ST
        • Vito Russo
          ... From: Stefan Trethan To: Sent: Wednesday, November 03, 2004 12:48 PM Subject: Re:
          Message 4 of 16 , Nov 3, 2004
            ----- Original Message -----
            From: "Stefan Trethan" <stefan_trethan@...>
            To: <Electronics_101@yahoogroups.com>
            Sent: Wednesday, November 03, 2004 12:48 PM
            Subject: Re: [Electronics_101] Open Antenna becames Quiet Relay


            >
            > On Wed, 3 Nov 2004 12:40:08 +0100, Vito Russo <vrusso@...> wrote:
            >
            > >
            > > I've understood too late that there could be a misunderstanding using
            > > only
            > > "noise"..
            > > Yes, I'm speaking of soundwaves.
            > > The demo equipment should be placed in a library, so it's not acceptable
            > > to
            > > hear a continous TIC TAC..
            > >
            > > Vito
            >
            > so the problem is the switching noise of the relay?
            >
            > get the most silent one you can find and put it in a noise box.
            > efficient noise blocking requires layers of acoustic very dense and very
            > light materials.
            > e.g. cushion the relay with foam, put it in a steel box made of 5mm steel
            > plate. cushion this
            > box with another layer of foam. should be totally silent.
            >
            > the secret to kill noise to dampen the mechanic oscillation (noise through
            > solids) by using
            > a high impedance conductor (foam) and feed it into a lot of weight. it is
            > not able to drive the
            > weight. The second secret is to prevent sound waves through air. enclosing
            > in foam.
            >
            > If you don't want to use steel to make box i found that small sandbags
            > (plastc kitchen bags filled with sand) work very well. just wrap it in
            > alternating layers of sand and foam.
            >

            Noise suppression is a good idea, but it's better to avoid steel. I can try
            to use sand and foam, but there's not much spare room to place them.

            > But keep in mind the number of switching cycles of a relay is limited, so
            > continuous click-clack is no good.

            Yes, the relay lifetime its a problem.
            The equipment purpose is to control the access to a library using RFid
            technique. The relays are part of the RFid system. We are planning to use a
            secondary detection equipment, for example a motion sensor or similar, to
            turn on the RFid system only when needed. Doing this way I hope we can raise
            the lifetime, there will be relay switches only when a person is walking
            through the controll access passage.

            >
            > ST
            >

            Vito

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          • Stefan Trethan
            ... Why must the antennas be switched at all? that is to be avoided IMO. if not possible then there should be two RX systems, duplicate all down to a level
            Message 5 of 16 , Nov 3, 2004
              On Wed, 3 Nov 2004 13:09:49 +0100, Vito Russo <vrusso@...> wrote:

              >
              > Yes, the relay lifetime its a problem.
              > The equipment purpose is to control the access to a library using RFid
              > technique. The relays are part of the RFid system. We are planning to
              > use a
              > secondary detection equipment, for example a motion sensor or similar, to
              > turn on the RFid system only when needed. Doing this way I hope we can
              > raise
              > the lifetime, there will be relay switches only when a person is walking
              > through the controll access passage.


              Why must the antennas be switched at all? that is to be avoided IMO.
              if not possible then there should be two RX systems, duplicate all down
              to a level where you can easily switch the signals electronically.
              Are there any solid state antenna switches? i guess not but who knows?

              do the maths, how many people a day, and how many cycles has the relay.

              ST
            • Vito Russo
              ... From: Stefan Trethan To: Sent: Wednesday, November 03, 2004 1:14 PM Subject: Re:
              Message 6 of 16 , Nov 3, 2004
                ----- Original Message -----
                From: "Stefan Trethan" <stefan_trethan@...>
                To: <Electronics_101@yahoogroups.com>
                Sent: Wednesday, November 03, 2004 1:14 PM
                Subject: Re: [Electronics_101] Open Antenna becames Quiet Relay


                >
                > On Wed, 3 Nov 2004 13:09:49 +0100, Vito Russo <vrusso@...> wrote:
                >
                > >
                > > Yes, the relay lifetime its a problem.
                > > The equipment purpose is to control the access to a library using RFid
                > > technique. The relays are part of the RFid system. We are planning to
                > > use a
                > > secondary detection equipment, for example a motion sensor or similar,
                to
                > > turn on the RFid system only when needed. Doing this way I hope we can
                > > raise
                > > the lifetime, there will be relay switches only when a person is walking
                > > through the controll access passage.
                >
                >
                > Why must the antennas be switched at all? that is to be avoided IMO.
                > if not possible then there should be two RX systems, duplicate all down
                > to a level where you can easily switch the signals electronically.
                > Are there any solid state antenna switches? i guess not but who knows?

                The antennas are not only switched but opened too. This is done to avoid
                mutual induction between them, because they are very near each other.

                >
                > do the maths, how many people a day, and how many cycles has the relay.

                I've done the calculations, but I don't know if I can trust the relay
                datasheets. Usually the number is always the same, 10^8 cycles. Some relay
                makers say this is the average rating, other say this is the minimum
                guaranteed. The average doesn't mean anything when you are considering the
                worst case, I need a statistical description, but I don't think that the
                maker can show me it.
                However, from the calculation, I find out that if I continuosly switch the
                relay, the equipment life should be 1.5 years.
                Considering that is not a very crowded place (a library full of ancient holy
                books), I can guess a gross extimation of 1 person per minute walking trough
                the passage for 5 second, that leads to 18 years of service, 36 years if you
                consider that during night time there will be no visitors. Probably in such
                a long time I must take into consideration also phenomenon such as oxidation
                or similar.
                But, I don't trust the datasheets..

                >
                > ST

                Vito

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              • Stefan Trethan
                ... Why can t you use 1 antenna only? ... there you are not the only one. but i think it might be OK. i think you can dampen the relay sound enough so it isn t
                Message 7 of 16 , Nov 3, 2004
                  >> Why must the antennas be switched at all? that is to be avoided IMO.
                  >> if not possible then there should be two RX systems, duplicate all down
                  >> to a level where you can easily switch the signals electronically.
                  >> Are there any solid state antenna switches? i guess not but who knows?
                  >
                  > The antennas are not only switched but opened too. This is done to avoid
                  > mutual induction between them, because they are very near each other.
                  >

                  Why can't you use 1 antenna only?

                  > But, I don't trust the datasheets..

                  there you are not the only one. but i think it might be OK.

                  i think you can dampen the relay sound enough so it isn't disturbing the
                  holy books ;-).
                  Maybe you can reduce the drive voltage/current so that the speed/force is
                  reduced.
                  check what the minimum is and use only a bit above. Of course the
                  construction of the relay is
                  also a big factor. something like a reed relais would be most silent, but
                  i'm not sure if they
                  are made for HF. I'd order a few and try. A simple foam isolation or
                  enclosure is probably well enough to reduce noise below noticeable level
                  (or below walking noise of the person).

                  ST
                • Vito Russo
                  ... From: Stefan Trethan To: Sent: Wednesday, November 03, 2004 2:38 PM Subject: Re:
                  Message 8 of 16 , Nov 3, 2004
                    ----- Original Message -----
                    From: "Stefan Trethan" <stefan_trethan@...>
                    To: <Electronics_101@yahoogroups.com>
                    Sent: Wednesday, November 03, 2004 2:38 PM
                    Subject: Re: [Electronics_101] Open Antenna becames Quiet Relay


                    >
                    >
                    > >> Why must the antennas be switched at all? that is to be avoided IMO.
                    > >> if not possible then there should be two RX systems, duplicate all down
                    > >> to a level where you can easily switch the signals electronically.
                    > >> Are there any solid state antenna switches? i guess not but who knows?
                    > >
                    > > The antennas are not only switched but opened too. This is done to avoid
                    > > mutual induction between them, because they are very near each other.
                    > >
                    >
                    > Why can't you use 1 antenna only?

                    Using the an huge antenna we found out that if the tag carried by the person
                    was orientend in some defined positions it was impossible to detect.
                    So we tried to place small antennas near each other, oriented in different
                    directions and placed at differnet heights. Only one antenna is active in
                    the same instant, but we switch very quickly among the antennas. Doing this
                    we cover the same range of the huge antenna, we are able to detect a tag
                    even if the carrier is running though the passage and there are no
                    undectable positions. The structure is more complex but performs better.

                    >
                    > > But, I don't trust the datasheets..
                    >
                    > there you are not the only one. but i think it might be OK.
                    >
                    > i think you can dampen the relay sound enough so it isn't disturbing the
                    > holy books ;-).
                    > Maybe you can reduce the drive voltage/current so that the speed/force is
                    > reduced.
                    > check what the minimum is and use only a bit above. Of course the
                    > construction of the relay is
                    > also a big factor. something like a reed relais would be most silent, but
                    > i'm not sure if they
                    > are made for HF. I'd order a few and try. A simple foam isolation or
                    > enclosure is probably well enough to reduce noise below noticeable level
                    > (or below walking noise of the person).

                    Uh, I was ordering reed relay at Farnell's.. well, I'll try them in the next
                    days. I hope they works for HF too.

                    >
                    > ST
                    >
                    >
                    >
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                    >
                    >
                  • Phil
                    Head noise in disk drives is a function of a number of things that are controllable (seek distance, head step rate, seek order, etc). The relay has only one
                    Message 9 of 16 , Nov 3, 2004
                      Head noise in disk drives is a function of a number of things that
                      are controllable (seek distance, head step rate, seek order, etc).
                      The relay has only one thing you can control, the coil.

                      Assuming that the pull-in noise is the issue, maybe you could PWM the
                      coil to make for a "softer" switch. Worth a try. I don't know how
                      that would effect life span of the contacts (more arcing?). The goal
                      would be to reduce the speed of the contacts which would reduce the
                      mechanical vibrations that are then becomming acoustic noise.

                      Secondly, look at how your relay is mounted. Is it on a PCB which is
                      acting like a sounding board (like the face of a guitar). If so,
                      placing deadening foam under the PCB where the relay is should help a
                      lot.
                    • Roy J. Tellason
                      ... I would tend to disagree with this. Mechanical construction is going to have a lot of effect here, I d think. I have one box that has a number of
                      Message 10 of 16 , Nov 3, 2004
                        On Wednesday 03 November 2004 12:27 pm, Phil wrote:
                        > Head noise in disk drives is a function of a number of things that
                        > are controllable (seek distance, head step rate, seek order, etc).

                        I would tend to disagree with this. Mechanical construction is going to have
                        a lot of effect here, I'd think. I have one box that has a number of
                        similarly-sized drives in it but they're different brands, and sound *quite*
                        different.

                        > The relay has only one thing you can control, the coil.
                        >
                        > Assuming that the pull-in noise is the issue, maybe you could PWM the
                        > coil to make for a "softer" switch. Worth a try. I don't know how
                        > that would effect life span of the contacts (more arcing?). The goal
                        > would be to reduce the speed of the contacts which would reduce the
                        > mechanical vibrations that are then becomming acoustic noise.

                        Then there's the fact that it takes a certain amount of magnetic force to
                        overcome the inertia, and a whole lot less to hold the contact in place.
                        You'd need a timing curve...

                        > Secondly, look at how your relay is mounted. Is it on a PCB which is
                        > acting like a sounding board (like the face of a guitar). If so,
                        > placing deadening foam under the PCB where the relay is should help a
                        > lot.

                        That strikes me as a good idea.
                      • Steve
                        Why not use tried and true technology? PIN diode switching. Look in Links in RF, for anything concerning Doppler Direction Finding. They switch 2 to 16
                        Message 11 of 16 , Nov 3, 2004
                          Why not use tried and true technology? PIN diode switching.

                          Look in Links in RF, for anything concerning Doppler Direction
                          Finding. They switch 2 to 16 antennas at rates from 1KHz to 200KHz
                          using PIN diodes, something you could -never- do with relays.

                          Steve Greenfield
                        • Stefan Trethan
                          ... best idea so far. st
                          Message 12 of 16 , Nov 3, 2004
                            On Wed, 03 Nov 2004 20:27:33 -0000, Steve <alienrelics@...> wrote:

                            >
                            >
                            > Why not use tried and true technology? PIN diode switching.
                            >
                            > Look in Links in RF, for anything concerning Doppler Direction
                            > Finding. They switch 2 to 16 antennas at rates from 1KHz to 200KHz
                            > using PIN diodes, something you could -never- do with relays.
                            >
                            > Steve Greenfield
                            >

                            best idea so far.

                            st
                          • Phil
                            ... going to have ... of ... sound *quite* ... sure but we re talking about what is controllable via programming... ... the ... how ... goal ... the ... force
                            Message 13 of 16 , Nov 3, 2004
                              --- In Electronics_101@yahoogroups.com, "Roy J. Tellason"
                              <rtellason@b...> wrote:
                              > On Wednesday 03 November 2004 12:27 pm, Phil wrote:
                              > > Head noise in disk drives is a function of a number of things that
                              > > are controllable (seek distance, head step rate, seek order, etc).
                              >
                              > I would tend to disagree with this. Mechanical construction is
                              going to have
                              > a lot of effect here, I'd think. I have one box that has a number
                              of
                              > similarly-sized drives in it but they're different brands, and
                              sound *quite*
                              > different.

                              sure but we're talking about what is controllable via programming...

                              >
                              > > The relay has only one thing you can control, the coil.
                              > >
                              > > Assuming that the pull-in noise is the issue, maybe you could PWM
                              the
                              > > coil to make for a "softer" switch. Worth a try. I don't know
                              how
                              > > that would effect life span of the contacts (more arcing?). The
                              goal
                              > > would be to reduce the speed of the contacts which would reduce
                              the
                              > > mechanical vibrations that are then becomming acoustic noise.
                              >
                              > Then there's the fact that it takes a certain amount of magnetic
                              force to
                              > overcome the inertia, and a whole lot less to hold the contact in
                              place.
                              > You'd need a timing curve...

                              Well, yes but a first approximation is probably going to help a lot.
                              The pull-in voltage is usually well below the rated voltage (30-40%
                              often) so even just PWM at a lower level should reduce the force of
                              pull-in and, theoretically, reduce the noise. I agree that a higher
                              RMS (i.e. larger duty cycle) pulse to get it started pulling in and
                              then even lower to finish it would probably be good but that may take
                              some time to figure out and holding force isn't the issue on noise.

                              By the way, a (possibly) simple thing to do is just adjust down the
                              coil voltage as low as possible to get it to close. That should
                              reduce the pull-in force and maybe reduce the noise.
                            • Stefan Trethan
                              ... i did suggest that several posts ago ;-) What do you guys think, is there any arcing when switching antennas? ST
                              Message 14 of 16 , Nov 3, 2004
                                On Wed, 03 Nov 2004 23:02:21 -0000, Phil <phil1960us@...> wrote:

                                >
                                > By the way, a (possibly) simple thing to do is just adjust down the
                                > coil voltage as low as possible to get it to close. That should
                                > reduce the pull-in force and maybe reduce the noise.
                                >


                                i did suggest that several posts ago ;-)

                                What do you guys think, is there any arcing when switching antennas?

                                ST
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