Automate turning of manual rotary switch?
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From: John Fields on 31 Mar 2010 14:28 On Wed, 31 Mar 2010 08:29:08 -0700 (PDT), Chris <christofire(a)talktalk.net> wrote: >On 31 Mar, 15:54, "markp" <map.nos...(a)f2s.com> wrote: >> Got a little problem. I've been asked to come up with something that turns a >> manual 3 way rotary switch from one position to another and back again under >> software control. The switch is one of those bulky things with a pointer >> style knob. They basically want to control a piece of equipment without >> modifying it in any way. >> >> Does anyone know of a switch actuator manufacturer? I'm looking for >> something I can place over the switch with a motor or solenoid to turn the >> switch (about 45 degrees per switch position). >> >> Thanks! >> >> Mark. > > >A Ledex switch perhaps, like http://www.surplussales.com/switches/SWLedex-1.html --- "I've been asked to come up with something that turns a manual 3 way rotary switch from one position to another and back again under software control." I don't think a LEDEX switch can do "and back again". JF
From: Tim Wescott on 31 Mar 2010 14:34 markp wrote: > Got a little problem. I've been asked to come up with something that turns a > manual 3 way rotary switch from one position to another and back again under > software control. The switch is one of those bulky things with a pointer > style knob. They basically want to control a piece of equipment without > modifying it in any way. > > Does anyone know of a switch actuator manufacturer? I'm looking for > something I can place over the switch with a motor or solenoid to turn the > switch (about 45 degrees per switch position). I'll bet that you're doomed to rolling your own, but I'd sure do those suggested web searches. Motor -> gear -> adapter on the mechanical side, position feedback -> processor -> software -> drive -> motor on the electro-software side. Can you remove the knob and attach directly to the shaft, or do 'they' want you to leave the knob on? Does it have to work under manual control when the software isn't diddling with it? How much individual adjustment are you allowed? How can you anchor this gizmo to the equipment? In principle this is a snap, but in reality there's some effort to make it all work. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
From: Jon Kirwan on 31 Mar 2010 15:37 On Wed, 31 Mar 2010 15:54:50 +0100, "markp" <map.nospam(a)f2s.com> wrote: >Got a little problem. I've been asked to come up with something that turns a >manual 3 way rotary switch from one position to another and back again under >software control. The switch is one of those bulky things with a pointer >style knob. They basically want to control a piece of equipment without >modifying it in any way. > >Does anyone know of a switch actuator manufacturer? I'm looking for >something I can place over the switch with a motor or solenoid to turn the >switch (about 45 degrees per switch position). I don't. But you reminded me of a remove control TV I used to have. It used a few metal bars that were "hammered" when you pushed a mechanical button. (Basically, tuning forks.) These emitted a precise audible tone which was decoded and used by the TV set to cause the tuner to move left or right (you had one control for each.) The TV could be set while sitting in a rocking chair from across the room! The knob was _also_ designed as a standard manual tuner so the remote wasn't required, at all. You could, of course, use the TV as a "normal" TV of the time where you had to get up and switch channels by hand. Of course, manufacturers soon got rid of the manual tuner assemblies and digitized these and then began using buttons and remote controls which, today, seem more necessary than mere convenience, anymore. Interesting question. Jon
From: whit3rd on 31 Mar 2010 16:46 On Mar 31, 7:54 am, "markp" <map.nos...(a)f2s.com> wrote: > Got a little problem. I've been asked to come up with something that turns a > manual 3 way rotary switch from one position to another and back again under > software control. Your basic requirement is a torque-limited (so it doesn't break the shaft) reversible motor that senses the clickstops of the switch (or that has some springy coupling and can relax between changes). Simply attaching a motor will not work, because it might park the switch between positions. I'd suggest a rotary position encoder (five bit Gray code is plenty) and a stepper motor with a forward/reverse/release control. It's generally easier to modify the box than to mount this kind of thing to its control cluster, though.
From: markp on 31 Mar 2010 17:18
"Tim Wescott" <tim(a)seemywebsite.now> wrote in message news:5qednQCgAZgvCC7WnZ2dnUVZ_rGdnZ2d(a)web-ster.com... > markp wrote: >> Got a little problem. I've been asked to come up with something that >> turns a manual 3 way rotary switch from one position to another and back >> again under software control. The switch is one of those bulky things >> with a pointer style knob. They basically want to control a piece of >> equipment without modifying it in any way. >> >> Does anyone know of a switch actuator manufacturer? I'm looking for >> something I can place over the switch with a motor or solenoid to turn >> the switch (about 45 degrees per switch position). > > I'll bet that you're doomed to rolling your own, but I'd sure do those > suggested web searches. Indeed, but this is a one-off so a ahnd crafted solution would be OK (as long as it's reliable!) > > Motor -> gear -> adapter on the mechanical side, position feedback -> > processor -> software -> drive -> motor on the electro-software side. > > Can you remove the knob and attach directly to the shaft, or do 'they' > want you to leave the knob on? Ideally leave the knob on, but could remove it and replace it. I'm not sure whether the knob is press-fitted or screwed. > Does it have to work under manual control when the software isn't diddling > with it? No, there will be a little control box with a manual override so all done in software. > How much individual adjustment are you allowed? How can you anchor this > gizmo to the equipment? Good question. There are some existing fixings I could attach to, I'm sure they could accept a few holes drilled in the panel that has the switch. > > In principle this is a snap, but in reality there's some effort to make it > all work. > > -- > Tim Wescott > Control system and signal processing consulting > www.wescottdesign.com This might be quite a tough mechanical challenge, as you say it sounds easy but the devil is in the details. The switch has click positions, I may need a way to sense it has seated properly in a particular position. Also I don't want this to ever sit just off centre of a position in case the switch contacts arc. Mark. |