Loading ...
Sorry, an error occurred while loading the content.

Paper shredder "jam" indicator

Expand Messages
  • Dave C
    A commercial-grade paper shredder has indicators for bin full and paper jam . The bin full indicator consists of an IR beam across the top of the bin. It is
    Message 1 of 20 , Nov 15, 2012
    • 0 Attachment
      A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.

      I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.

      The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.

      A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.

      Any idea how such a device would detect a jam? Just curious...

      Thanks,
      Dave

      [Non-text portions of this message have been removed]
    • Willie Pierce
      The shredder I use... I ve looked it over and I m thinking it has to do with pressure on the blades. Excessive pressure= jam. The ir is for how full the bin
      Message 2 of 20 , Nov 15, 2012
      • 0 Attachment
        The shredder I use...

        I've looked it over and I'm thinking it has to do with pressure on the blades. Excessive pressure= jam. The ir is for how full the bin is and when beam Breaks... Jam

        Sent from my iPhone

        On Nov 15, 2012, at 2:00 PM, Dave C <davec2468@...> wrote:

        > A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.
        >
        > I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.
        >
        > The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.
        >
        > A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.
        >
        > Any idea how such a device would detect a jam? Just curious...
        >
        > Thanks,
        > Dave
        >
        > [Non-text portions of this message have been removed]
        >
        >


        [Non-text portions of this message have been removed]
      • Jeffrey Engel
        Motor RPM? Maybe the 51 looks for paper falling past the bin full detector? Now I m curious, too.  Please let us know what you find out.   Jeff Happiness
        Message 3 of 20 , Nov 15, 2012
        • 0 Attachment
          Motor RPM?

          Maybe the '51 looks for paper falling past the 'bin full' detector?


          Now I'm curious, too.  Please let us know what you find out.

           
          Jeff

          Happiness is - positive intake manifold pressure.


          ________________________________
          From: Dave C <davec2468@...>
          To: Electronics101 <Electronics_101@yahoogroups.com>
          Sent: Thursday, November 15, 2012 2:00 PM
          Subject: [Electronics_101] Paper shredder "jam" indicator


           
          A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.

          I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.

          The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.

          A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.

          Any idea how such a device would detect a jam? Just curious...

          Thanks,
          Dave

          [Non-text portions of this message have been removed]




          [Non-text portions of this message have been removed]
        • jong kung
          ... 80C51 is pretty hefty processor - it can easily take sensor input (to detect if rotation has stopped). Maybe there s a magnetic sensor, rotation sensor
          Message 4 of 20 , Nov 15, 2012
          • 0 Attachment
            > I don't know how a jam is detected. There is an another IR
            > pair at the top of the cutting rollers to turn on the motor,
            > but no other sensors.
            >
            > The motor is a mains-voltage AC with dual windings (forward,
            > reverse). There is no large series resistance in the motor
            > path that would be used for current sensing nor motor
            > speed.
            >
            > A Philips-flavor 80C51 (87LPC762) conducts the whole show,
            > and turns on and off the indicators.

            80C51 is pretty hefty processor - it can easily take sensor input (to detect if rotation has stopped). Maybe there's a magnetic sensor, rotation sensor that tells the CPU the cutters / rollers stopped moving.


            Jong
          • Dave C
            ... And how is excessive pressure detected? ... No, when the Full Bin beam is broken... Full Bin. Dave
            Message 5 of 20 , Nov 15, 2012
            • 0 Attachment
              On 15 November 2012, at 3:02 PM, Willie Pierce wrote:

              > The shredder I use...
              >
              > I've looked it over and I'm thinking it has to do with pressure on the blades. Excessive pressure= jam.

              And how is "excessive pressure" detected?

              > The ir is for how full the bin is and when beam Breaks... Jam

              No, when the Full Bin beam is broken... Full Bin.

              Dave
            • Dave C
              ... No tach on the motor. ... The sensor is offset from the output of the cutter. ... You ll be the 2nd to know! ;-) ... Dave
              Message 6 of 20 , Nov 15, 2012
              • 0 Attachment
                On 15 November 2012, at 4:07 PM, Jeffrey Engel wrote:

                > Motor RPM?

                No tach on the motor.

                > Maybe the '51 looks for paper falling past the 'bin full' detector?

                The sensor is offset from the output of the cutter.

                > Now I'm curious, too. Please let us know what you find out.

                You'll be the 2nd to know! ;-)

                > Jeff

                Dave
              • Dave C
                ... No sensors other than Bin Full and the sensor at the input of the cutters. Dave [Non-text portions of this message have been removed]
                Message 7 of 20 , Nov 15, 2012
                • 0 Attachment
                  On 15 November 2012, at 5:00 PM, jong kung wrote:

                  > 80C51 is pretty hefty processor - it can easily take sensor input (to detect if rotation has stopped). Maybe there's a magnetic sensor, rotation sensor that tells the CPU the cutters / rollers stopped moving.
                  >
                  > Jong

                  No sensors other than Bin Full and the sensor at the input of the cutters.

                  Dave

                  [Non-text portions of this message have been removed]
                • Donald H Locker
                  Jam would be indicated if motor current exceeds some level for a period of time after startup. That would not require a separate (visible) sensor. Donald. --
                  Message 8 of 20 , Nov 16, 2012
                  • 0 Attachment
                    Jam would be indicated if motor current exceeds some level for a period of time after startup. That would not require a separate (visible) sensor.

                    Donald.
                    --
                    *Plain Text* email -- it's an accessibility issue
                    () no proprietary attachments; no html mail
                    /\ ascii ribbon campaign - <www.asciiribbon.org>

                    ----- Original Message -----
                    > From: "Dave C" <davec2468@...>
                    > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                    > Sent: Friday, November 16, 2012 1:08:17 AM
                    > Subject: Re: [Electronics_101] Paper shredder "jam" indicator
                    > On 15 November 2012, at 5:00 PM, jong kung wrote:
                    >
                    > > 80C51 is pretty hefty processor - it can easily take sensor input
                    > > (to detect if rotation has stopped). Maybe there's a magnetic
                    > > sensor, rotation sensor that tells the CPU the cutters / rollers
                    > > stopped moving.
                    > >
                    > > Jong
                    >
                    > No sensors other than Bin Full and the sensor at the input of the
                    > cutters.
                    >
                    > Dave
                    >
                    > [Non-text portions of this message have been removed]
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > Please trim excess when replyingYahoo! Groups Links
                    >
                    >
                    >
                  • Andrew Mathison (Alice)
                    A possible method is to detect the current through the motor. This can be done in several ways. A simple one is to wrap a coil of wire around a reed relay, so
                    Message 9 of 20 , Nov 16, 2012
                    • 0 Attachment
                      A possible method is to detect the current through the motor. This can be
                      done in several ways. A simple one is to wrap a coil of wire around a reed
                      relay, so that when the current exceeds a certain value, the relay operates
                      and switches a LED on or whatever.

                      If the motor is AC, you will need to place the coil/relay (now to be called
                      the sensor), in the middle of a full wave rectifier so that the motor still
                      gets AC, but the coil sees current from both directions, but then in the
                      same direction at that point. I can produce a diagram if needed, but it is
                      very simple.

                      The wire used must handle full load current when stalled without heating.
                      The number of turns will probably need to be empirically found.

                      Instead of the sensor, a resistor of low value could be used, with a wattage
                      that would allow full load current to be passed without undue heating, then
                      monitor the voltage drop across that resistor in some simple way, even a LED
                      might be OK with a series resistor to prevent burnout.....

                      There must be a great deal more possible method, but these are fairly
                      simple.......

                      Detection of commutation is a further possible method, assuming that the
                      motor is a Universal type with a commutator for example, or even if it is a
                      brushless DC type. I believe that there are chips around for this used on PC
                      mainboards to detect fan motors turning.

                      Even painting black/white stripes on a moving part and then "watching it"
                      using an IR LED and IR detector (they cost only pennies nowadays), would
                      allow movement or not to be detected.....

                      Not knowing what type the motor is exactly precludes anything
                      further.....but I hope that this causes a few ideas to be produced...

                      Regards

                      Andy
                    • Stefan Trethan
                      I think you must be missing the motor current sensing element. It is the obvious and reliable method. What the heck do they need a microprocessor for is what
                      Message 10 of 20 , Nov 16, 2012
                      • 0 Attachment
                        I think you must be missing the motor current sensing element. It is
                        the obvious and reliable method.

                        What the heck do they need a microprocessor for is what I'm asking myself......

                        ST

                        On Thu, Nov 15, 2012 at 9:00 PM, Dave C <davec2468@...> wrote:
                        > A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.
                        >
                        > I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.
                        >
                        > The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.
                        >
                        > A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.
                        >
                        > Any idea how such a device would detect a jam? Just curious...
                        >
                        > Thanks,
                        > Dave
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >
                        >
                        > ------------------------------------
                        >
                        > Please trim excess when replyingYahoo! Groups Links
                        >
                        >
                        >
                      • Dave C
                        I, too, was a bit impressed to find a uP in this thing. Without a fancy human sensor (some models have a proximity -- or was it a contact type -- sensor near
                        Message 11 of 20 , Nov 16, 2012
                        • 0 Attachment
                          I, too, was a bit impressed to find a uP in this thing. Without a fancy human sensor (some models have a proximity -- or was it a contact type -- sensor near the document input) much of this can be done with relay logic of very low parts count. Maybe this uP -- as programmed -- shares many models so cost is relatively low compared with redesigning a new PCB?

                          The current sensor must be a large, small-value resistor, if I'm not mistaken. There is no such component:

                          http://tinypic.com/view.php?pic=11sz607&s=6

                          The (physically) largest resistor is near the left end: a 1/4(?) watt 1K flame-proof. A bit high for current sensing, I think?

                          Thanks,
                          Dave

                          -=-=-=-

                          On 16 November 2012, at 9:51 AM, Stefan Trethan wrote:

                          > I think you must be missing the motor current sensing element. It is
                          > the obvious and reliable method.
                          >
                          > What the heck do they need a microprocessor for is what I'm asking myself......
                          >
                          > ST
                          >
                          > On Thu, Nov 15, 2012 at 9:00 PM, Dave C <davec2468@...> wrote:
                          >> A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.
                          >>
                          >> I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.
                          >>
                          >> The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.
                          >>
                          >> A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.
                          >>
                          >> Any idea how such a device would detect a jam? Just curious...
                          >>
                          >> Thanks,
                          >> Dave
                        • Dave C
                          Thanks Andy for the motor current primer. Nice to know the many ways... This motor is -- as far as my knowledge of motors will let me identify it -- a
                          Message 12 of 20 , Nov 16, 2012
                          • 0 Attachment
                            Thanks Andy for the motor current primer. Nice to know the many ways...

                            This motor is -- as far as my knowledge of motors will let me identify it -- a brushless synchronous type with 2 windings: forward & reverse. In any case it has only 3 wires to it: neutral and F & R leads. No other wires.

                            The PCB (see separate post with link to PCB phoo) uses a Triac to turn the motor on and off, and a SPDP relay to choose F or R mode. Pretty simple on the motor control end of things.

                            Cheers,
                            Dave

                            -=-=-=-

                            > A possible method is to detect the current through the motor. This can be
                            > done in several ways. A simple one is to wrap a coil of wire around a reed
                            > relay, so that when the current exceeds a certain value, the relay operates
                            > and switches a LED on or whatever.
                            >
                            > If the motor is AC, you will need to place the coil/relay (now to be called
                            > the sensor), in the middle of a full wave rectifier so that the motor still
                            > gets AC, but the coil sees current from both directions, but then in the
                            > same direction at that point. I can produce a diagram if needed, but it is
                            > very simple.
                            >
                            > The wire used must handle full load current when stalled without heating.
                            > The number of turns will probably need to be empirically found.
                            >
                            > Instead of the sensor, a resistor of low value could be used, with a wattage
                            > that would allow full load current to be passed without undue heating, then
                            > monitor the voltage drop across that resistor in some simple way, even a LED
                            > might be OK with a series resistor to prevent burnout.....
                            >
                            > There must be a great deal more possible method, but these are fairly
                            > simple.......
                            >
                            > Detection of commutation is a further possible method, assuming that the
                            > motor is a Universal type with a commutator for example, or even if it is a
                            > brushless DC type. I believe that there are chips around for this used on PC
                            > mainboards to detect fan motors turning.
                            >
                            > Even painting black/white stripes on a moving part and then "watching it"
                            > using an IR LED and IR detector (they cost only pennies nowadays), would
                            > allow movement or not to be detected.....
                            >
                            > Not knowing what type the motor is exactly precludes anything
                            > further.....but I hope that this causes a few ideas to be produced...
                            >
                            > Regards
                            >
                            > Andy
                          • Dave C
                            ... The small wires leading away from the PCB are to two IR emitter & sensor pairs: jam detect and paper input detect. Dave
                            Message 13 of 20 , Nov 16, 2012
                            • 0 Attachment
                              > http://tinypic.com/view.php?pic=11sz607&s=6

                              The small wires leading away from the PCB are to two IR emitter & sensor pairs: jam detect and paper input detect.

                              Dave
                            • Willie Pierce
                              I have a fairly cheap shredder it s lights indicate jam, forward or reverse when the bin fills it displays the same light as jam. Sent from my iPhone ...
                              Message 14 of 20 , Nov 16, 2012
                              • 0 Attachment
                                I have a fairly cheap shredder it's lights indicate jam, forward or reverse when the bin fills it displays the same light as jam.

                                Sent from my iPhone

                                On Nov 16, 2012, at 12:02 AM, Dave C <davec2468@...> wrote:

                                > On 15 November 2012, at 3:02 PM, Willie Pierce wrote:
                                >
                                > > The shredder I use...
                                > >
                                > > I've looked it over and I'm thinking it has to do with pressure on the blades. Excessive pressure= jam.
                                >
                                > And how is "excessive pressure" detected?
                                >
                                > > The ir is for how full the bin is and when beam Breaks... Jam
                                >
                                > No, when the Full Bin beam is broken... Full Bin.
                                >
                                > Dave
                                >
                                >


                                [Non-text portions of this message have been removed]
                              • Willie Pierce
                                As for pressure I was figuring something along the lines of a current sensor. When the motor draws over x voltage then jam light comes on. Sent from my iPhone
                                Message 15 of 20 , Nov 16, 2012
                                • 0 Attachment
                                  As for pressure I was figuring something along the lines of a current sensor. When the motor draws over x voltage then jam light comes on.

                                  Sent from my iPhone

                                  On Nov 16, 2012, at 12:02 AM, Dave C <davec2468@...> wrote:

                                  > On 15 November 2012, at 3:02 PM, Willie Pierce wrote:
                                  >
                                  > > The shredder I use...
                                  > >
                                  > > I've looked it over and I'm thinking it has to do with pressure on the blades. Excessive pressure= jam.
                                  >
                                  > And how is "excessive pressure" detected?
                                  >
                                  > > The ir is for how full the bin is and when beam Breaks... Jam
                                  >
                                  > No, when the Full Bin beam is broken... Full Bin.
                                  >
                                  > Dave
                                  >
                                  >


                                  [Non-text portions of this message have been removed]
                                • jong kung
                                  ... You know.... stuff.... Jong
                                  Message 16 of 20 , Nov 16, 2012
                                  • 0 Attachment
                                    > What the heck do they need a microprocessor for is what I'm
                                    > asking myself......

                                    You know.... stuff....


                                    Jong
                                  • Stefan Trethan
                                    There are other ways of sensing current, such as hall effect, inductive current transformer, or just using a PCB trace as shunt. Shunts don t have to be high
                                    Message 17 of 20 , Nov 16, 2012
                                    • 0 Attachment
                                      There are other ways of sensing current, such as hall effect,
                                      inductive current transformer, or just using a PCB trace as shunt.
                                      Shunts don't have to be high wattage if your sensing circuit is sensitive.
                                      That inductor left of the triac looks suspicious, how many connections
                                      does it have?

                                      ST


                                      On Fri, Nov 16, 2012 at 9:20 PM, Dave C <davec2468@...> wrote:
                                      > I, too, was a bit impressed to find a uP in this thing. Without a fancy human sensor (some models have a proximity -- or was it a contact type -- sensor near the document input) much of this can be done with relay logic of very low parts count. Maybe this uP -- as programmed -- shares many models so cost is relatively low compared with redesigning a new PCB?
                                      >
                                      > The current sensor must be a large, small-value resistor, if I'm not mistaken. There is no such component:
                                      >
                                      > http://tinypic.com/view.php?pic=11sz607&s=6
                                      >
                                      > The (physically) largest resistor is near the left end: a 1/4(?) watt 1K flame-proof. A bit high for current sensing, I think?
                                      >
                                      > Thanks,
                                      > Dave
                                      >
                                      > -=-=-=-
                                      >
                                      > On 16 November 2012, at 9:51 AM, Stefan Trethan wrote:
                                      >
                                      >> I think you must be missing the motor current sensing element. It is
                                      >> the obvious and reliable method.
                                      >>
                                      >> What the heck do they need a microprocessor for is what I'm asking myself......
                                      >>
                                      >> ST
                                      >>
                                      >> On Thu, Nov 15, 2012 at 9:00 PM, Dave C <davec2468@...> wrote:
                                      >>> A commercial-grade paper shredder has indicators for "bin full" and "paper jam". The bin full indicator consists of an IR beam across the top of the bin. It is tested and working.
                                      >>>
                                      >>> I don't know how a jam is detected. There is an another IR pair at the top of the cutting rollers to turn on the motor, but no other sensors.
                                      >>>
                                      >>> The motor is a mains-voltage AC with dual windings (forward, reverse). There is no large series resistance in the motor path that would be used for current sensing nor motor speed.
                                      >>>
                                      >>> A Philips-flavor 80C51 (87LPC762) conducts the whole show, and turns on and off the indicators.
                                      >>>
                                      >>> Any idea how such a device would detect a jam? Just curious...
                                      >>>
                                      >>> Thanks,
                                      >>> Dave
                                      >
                                      >
                                      > ------------------------------------
                                      >
                                      > Please trim excess when replyingYahoo! Groups Links
                                      >
                                      >
                                      >
                                    • Dave C
                                      Good eye, Stefan. It is a small transformer. The primary is in series between the mains fuse and the triac. The secondary feeds (as best I can figure it) a
                                      Message 18 of 20 , Nov 16, 2012
                                      • 0 Attachment
                                        Good eye, Stefan. It is a small transformer. The primary is in series between the mains fuse and the triac. The secondary feeds (as best I can figure it) a comparator pin of port 0 on the 80C51. That pot (with a blob of glue on the adjustment screw) looks like calibration for the jamb condition.

                                        Looks like this is the current sense method for a jam condition.

                                        I wonder why they used a pricey transformer like that rather than a simple shunt resistor...

                                        An aside: the IR emitter was wired backwards with the cathode to positive. The job looks like it was done at the factory -- no indication of repair or modification. I tested the emitter and it's dead -- after a few years of reverse polarity, I guess it's understandable. And this may explain why I acquired it all jammed up with a stripped plastic gear: I think the owner thought that it was to be operated manually: just turn it on and feed it paper; there was no automatic "start & stop" function when feeding paper. But it does bring up the question: why didn't the current sense circuit do its job?

                                        Thanks!
                                        Dave

                                        -=-=-=-

                                        > There are other ways of sensing current, such as hall effect,
                                        > inductive current transformer, or just using a PCB trace as shunt.
                                        > Shunts don't have to be high wattage if your sensing circuit is sensitive.
                                        > That inductor left of the triac looks suspicious, how many connections
                                        > does it have?
                                        >
                                        > ST
                                      • Stefan Trethan
                                        The reason to use the transformer is because it provides insulation to the mains, a shunt does not. ST
                                        Message 19 of 20 , Nov 17, 2012
                                        • 0 Attachment
                                          The reason to use the transformer is because it provides insulation to
                                          the mains, a shunt does not.

                                          ST

                                          On Sat, Nov 17, 2012 at 8:59 AM, Dave C <davec2468@...> wrote:
                                          > Good eye, Stefan. It is a small transformer. The primary is in series between the mains fuse and the triac. The secondary feeds (as best I can figure it) a comparator pin of port 0 on the 80C51. That pot (with a blob of glue on the adjustment screw) looks like calibration for the jamb condition.
                                          >
                                          > Looks like this is the current sense method for a jam condition.
                                          >
                                          > I wonder why they used a pricey transformer like that rather than a simple shunt resistor...
                                          >
                                          > An aside: the IR emitter was wired backwards with the cathode to positive. The job looks like it was done at the factory -- no indication of repair or modification. I tested the emitter and it's dead -- after a few years of reverse polarity, I guess it's understandable. And this may explain why I acquired it all jammed up with a stripped plastic gear: I think the owner thought that it was to be operated manually: just turn it on and feed it paper; there was no automatic "start & stop" function when feeding paper. But it does bring up the question: why didn't the current sense circuit do its job?
                                          >
                                          > Thanks!
                                          > Dave
                                          >
                                          > -=-=-=-
                                          >
                                          >> There are other ways of sensing current, such as hall effect,
                                          >> inductive current transformer, or just using a PCB trace as shunt.
                                          >> Shunts don't have to be high wattage if your sensing circuit is sensitive.
                                          >> That inductor left of the triac looks suspicious, how many connections
                                          >> does it have?
                                          >>
                                          >> ST
                                          >
                                          >
                                          > ------------------------------------
                                          >
                                          > Please trim excess when replyingYahoo! Groups Links
                                          >
                                          >
                                          >
                                        • Dave C
                                          Ah, of course... Dave --=-=-
                                          Message 20 of 20 , Nov 17, 2012
                                          • 0 Attachment
                                            Ah, of course...

                                            Dave

                                            --=-=-

                                            > The reason to use the transformer is because it provides insulation to
                                            > the mains, a shunt does not.
                                            >
                                            > ST
                                          Your message has been successfully submitted and would be delivered to recipients shortly.