Remotely controlling a rotary switch

[k4kyv]

I am in the think-tank mode for modifying my remote antenna tuning system so I don't have to run out to the tower every time I change bands.  I found a couple of identical, big-arse dual wafer ceramic rotary switches, each about 5" in diameter with 10 positions, indexed with spring loaded cams.  I would need to gang the two together and figure out some way to rotate the whole thing remotely. I think a reversible DC motor would be too difficult to configure so that it would automatically stop precisely every time at the proper position for each tap position on the switch.

I have seen mechanisms that rotated with a latching cam that looks kind of like a rotary saw blade.  A solenoid with a hook on the armature engages a tooth on the cam, and when activated, pulls the cam down one notch, then releases it. I would like to find something  like that ready-made or at least modifiable to work in my application.  Otherwise it will involve homebrewing from scratch, carving the parts out of hunks of solid steel, not exactly an easy task.

Anyone have anything lying around in the junk that might be made to work, or know of something easily available that would fit the bill?

[aafradio]

Ledex has traditionally been the primary supplier of these solenoids. 
http://www.ledex.com/rotary-solenoid/rotary-solenoid-comparison.html?gclid=CIaI-4r30aACFdk55Qodh0UC1Q
I'm sure I have a couple in the storage unit, but I have some doubts about them rotating a 5" diameter switch, since they are attached to a ~2" multi-pole gang of switches.  Do you have a required torque spec on the 5" switch?

73,
Mike  KC4TOS

[W2XR]

Ledex has traditionally been the primary supplier of these solenoids.  
http://www.ledex.com/rotary-solenoid/rotary-solenoid-comparison.html?gclid=CIaI-4r30aACFdk55Qodh0UC1Q
I'm sure I have a couple in the storage unit, but I have some doubts about them rotating a 5" diameter switch, since they are attached to a ~2" multi-pole gang of switches.  Do you have a required torque spec on the 5" switch?

73,
Mike  KC4TOS

Hi Mike,

That is a wonderful website you have created, pertaining to the B-17 and B-29 aircraft, and early Army Air force avionics equipment. Very nicely written, too.

http://aafradio.org

Anyone who is interested in aircraft and airborne electronics equipment of the Second World War period is encouraged to take a look.

I especially enjoyed the information and interior photos relating to the Enola Gay; this is, of course, the aircraft that dropped the atomic bomb on Hiroshima.

I did not know the Enola Gay had been moved from the Smithsonian to the museum you had referenced in Dallas. I may visiting Dallas later this summer; if so, I intend to pay her a visit.

Thank you for making this information available, Mike.

73,

Bruce

[aafradio]

My pleasure, Bruce. 

Regrettably, it's at Dulles, VA (IAD), not Dallas, TX.  It's about 18 miles west of the downtown National Air & Space Museum, and is known as the Udvar-Hazy Center - http://www.nasm.si.edu/UdvarHazy/

[KL7OF]

clothes and dish washing machines of the 80'sand 90's have solenoids and rotary switch timers and other parts that may be useful to your application....

[Ed/KB1HYS]

a power screwdriver, with a worm gear driving a standard gear, plenty of torque, reversible, and with a little ingeniuety you could put an indicator or stop on it.

Probably what you want is something like the TV antenna rotators with the repeater indicating switch position in the shack?  they arent' THAT big and have plenty of torque.  You could easily calibrate the dial face to show the switch positions. 

Just thinking out loud.

[W2XR]

My pleasure, Bruce.  

Regrettably, it's at Dulles, VA (IAD), not Dallas, TX.  It's about 18 miles west of the downtown National Air & Space Museum, and is known as the Udvar-Hazy Center - http://www.nasm.si.edu/UdvarHazy/

Thanks for the clarification, Mike. How I confused Dulles, VA and Dallas, TX is beyond me; I guess I could use age as an excuse.

The next time I am in that part of VA, I plan on scheduling a visit to the Udvar-Hazy Center. I would really enjoy seeing the Enola Gay, realizing of course, that the likelihood of getting inside the airplane is probably close to nonexistent.

Keep up the fine work of restoring the Enola Gay's avionics and interior. As an example, that kind of work makes the restoration of a '67 Corvette big-block to factory original/as-built condition seem like a veritable walk in the park. I'm fairly sure there are very little authentic OEM or reproduction parts available for B-29 restorations nowadays.

73,

Bruce

[aafradio]

The next time I am in that part of VA, I plan on scheduling a visit to the Udvar-Hazy Center. I would really enjoy seeing the Enola Gay, realizing of course, that the likelihood of getting inside the airplane is probably close to nonexistent.

You would not believe how many signatures it takes for me to get inside to install something I've restored.  Once the "artifact" is turned over to the collections staff by the restoration staff, it becomes a big deal.  Just part of the bureaucracy...  That's one reason I took so many photos of the interior and put them on the website.  On the other hand, the practicality of having thousands of grubby little hands rubbing the gubbins in the interior of a priceless aircraft should be obvious.  There are a few museums who have tours through one or two of their airframes and the yearly loss to theft and vandalism is just something they tolerate.  I wish there was some way to limit access to just hams or some other criteria, but the political consequences of such a proposed action is fairly predictable.

Keep up the fine work of restoring the Enola Gay's avionics and interior. As an example, that kind of work makes the restoration of a '67 Corvette big-block to factory original/as-built condition seem like a veritable walk in the park. I'm fairly sure there are very little authentic OEM or reproduction parts available for B-29 restorations nowadays.

That's actually how I got started in restoration work.  I used to restore Corvettes!  My last one was a ground-up '67 big block.  I was afraid to drive it when it was finished.  Also, the thought of getting under a car in my later years made me shift to old radios, which you could actually use without fear of someone scratching it or rear ending you at a stoplight...   Amazingly enough, I still pick up an occasional part for WWII aircraft avionics on ebay.  Recall that there were hundreds of millions of parts produced during the war, and there are still old warehouses here and there that have undiscovered corners.  I found an original aircraft ash tray in an old "empty" Glenn Martin plant in Baltimore the same way - http://aafradio.org/flightdeck/Peripherals-misc.html

[K5UJ]

Don, what do you want to switch?  you have, I think it was, two 10 pos. dual wafer switches?  do they have stops?  does the contact make with each tap one at a time or connect the current one plus all previous as it goes around?  Are you switching coil taps, feedlines, .padder caps, all of the above ...the reason for all the questions is it might be that rotary switches are not the best way to go.  Depending on what you want to do, you might have it easier and more reliable to have a switch network of relays.

Rob

[aafradio]

That would be my preference as well, Rob.  Back in the dark ages of my youth, if you wanted to switch something remotely, it was the only reasonable way to go.  A rotary switch is inherently a manually rotated device, though I can understand Don's reluctance to abandon such beautiful switches.

[WU2D]

I got over to Dulles the first year they had it open - WOW! I got to see the Enola Gay which is suspended overhead but you get to be 3 feet from the nose and just above the canopy so you can see right in close up.

They had lots of crazy stuff like the last SR-71 - the one that set the record on it's flight east on its wheels.

And they had the Enterprise OV-71 the first orbiter on its wheels.

And Air France donated an awesome SST which is somehow hanging in mid air.

This place is BIG.

And they had a lot of classic foes nose to nose like Zero vs P40 and MIG 15 vs Sabre and so on.

Mike WU2D

[k4kyv]

I have 5 different tuners that have to be switched, both input and output, some of them feeding open wire tuned feeders at a high voltage point.

Right now I do it with one manual rotary switch to select the input and the output is selected using a series of  DPDT knife switches thrown in a sequence to  form  kind of a logic circuit.  I  would need several high voltage ceramic insulated relays with wide spacing between the contacts, all with the same coil voltage.  Don't have anything like that in my junkbox, and a complete set would probably cost a fortune and take for ever to round up.

The wafer switches have spring loaded stops, so conceivably a shaft coupling with a certain amount of flexibility would get them close enough that the indexing stops would seat in proper position.  Coupling the shafts together would allow me to remove the stops from one of the  switches if it took too much torque to operate both.

[aafradio]

I assumed that from your first post.  Removing the stops from one switch is probably essential.  The Ledex style solenoids have quite a bit of torque, but you would have to try one of them to see whether it was enough.  The indexing is also something that will need to be looked at - they have a whole series of rotor angles that the solenoids are designed to turn.

[aafradio]

I got over to Dulles the first year they had it open - WOW! I got to see the Enola Gay which is suspended overhead but you get to be 3 feet from the nose and just above the canopy so you can see right in close up.

It's mounted on a pair of $100,000 scissors jacks to get it up in the air. The catwalk was a deliberate attempt to get you as close as possible, along with the extensive fiber optic lighting to allow you to see the inside lit up.  It's a shame the crazies forced the museum to mount the plexiglass wall between the public and the plane.  The unloaded weight of the aircraft makes for some interesting effects - the balance is normally nose heavy, but in its current condition, I've felt the nose wheel rise when I've been in the radar compartment.  (I've gone on a diet since then, so no nasty comments, please...)

And Air France donated an awesome SST which is somehow hanging in mid air.

The landing gear on the Concorde really jacks it up in the air an amazing distance, but it's not actually hung on cables.  The arched design of Udvar-Hazy was designed to hang a lot of tonnage, but it wouldn't support a Concorde...

[WA1GFZ]

Mike,
That wasn't the last SR71. That was the last one that made the news.
Yeasr later I heard one flying around Palmdale and a guy I work with saw it.
Bad ass sounding motors.

[KB2WIG]

Back in the '70's my brother and I went to the local SAC base.  Early morning, nothing to do.... Got to watch a '71 do touch-and-goes....

The last time around the pilot musta known a bunch of JNs was watching. He lit the afterburners, and she went straight up and up and went away......

klc

[k7yoo]

Don: I have been using large 24V solenoid type RF relays from Russia. They are available from a variety of the vendors on E-pay, QRO parts, etc. They work great for switching antennas and RF tank components. Picture attached
Since you already have rotary switches they are not all that hard to utilize. I assume the ones you have are similar to the T 368 bandswitch and have the really stiff roller follower that rides on an alloy or nylon camwheel. To drive this with a dc motor you must gang an additional wafer with the same indexing to run indicator lights. Use a DC motor like a headlight door (best) or window motor coupled with a LOOSE chain drive. When you do this the motor rotates the switch until the camfollower snaps to the next detent and the chain goes slack, allowing you time to get off the motor switch. This assures that the switch will stay solidly in the detent and contact will be made properly. Drake did this on the remote antenna switch accessory for the "C" line. I have one of the remote boxes if you want to borrow it to check out the operation. If you do not do this trying to time the "coast" on a DC drive will drive you nuts.
Skip

[KL7OF]

Don... Car door window motors....car antenna up and down motors....sunroof actuators..windshield wiper motors (that can move a rotary actuator 1 click with each rotation.......etc   12 volt and available at junk yard prices or free in some cases...lots of possibilities in the older auto world of parts...  good luck   Steve

[KL7OF]

Don....I've not tried this but the windshield wiper motor with the associated controls that allow the 1 wipe cycle might work very well....1 wipe cycle for each click of fhe rotary switch...a simple peg and cam system ..and windshield wiper motors are high torque.......just a thought

[Opcom]

How about old phone-type stepping switches? They have a lot of torque and many small steps. I have some that have contacts about half way around, and I don't know about how easy the shafts are to couple to, but they are strongg enough to turn other switches. I could take pics if you are interested in thinking about that possibility. otherwise the only thing I could suggest would be gearmotors and use reed relays to set the 'detents". There is an article in QST April, page 44 about this right now.

[k4kyv]

Ledex has traditionally been the primary supplier of these solenoids.  
http://www.ledex.com/rotary-solenoid/rotary-solenoid-comparison.html?gclid=CIaI-4r30aACFdk55Qodh0UC1Q
I'm sure I have a couple in the storage unit, but I have some doubts about them rotating a 5" diameter switch, since they are attached to a ~2" multi-pole gang of switches.  Do you have a required torque spec on the 5" switch?

Those look like they would be exactly what I need, except my switches are indexed at 36° per step and the closest thing they list is 35° per stroke. They mention something about building a special unit to order with custom stroke angle, but I suspect that would be way out of my price range. The 35° ones are close, but 1° error per step would accumulate too much error over 5 steps for the switch contacts to line up properly.

The round part of the ceramic wafers are actually 4" in diameter.  The 5" figure includes "ears" or protrusions on each side of the wafer, making it more like an oval shape, to accommodate the mounting hardware. With the spring removed from the detent cam, the switches rotate with very little torque. With the spring engaged, it takes considerable torque, but I haven't attempted to measure it.

I have several 12 vdc reversible gear motors that turn at about 1 rpm.  I used one of these, geared down further with a worm drive, to rotate the tuning cap on my 160m dipole tuner (before I  ran over the control cable with a lawnmower).  The torque is great enough that I can't stop it from turning by hand.  The problem is figuring out how to make it stop exactly for each switch position. On the 160m tuner, I used my el-cheapo SWR meter and and let it run till I hit a null on reflected power. But on this thing I want to be able to just hit the button and have it stop precisely in position each time.

I looked over the QST article, but I doubt the reed switches and magnet idea would be precise enough to make it always engage the detent cam precisely on.

[KX5JT]

Would not programmable stepper motors be the way to go for such a project?

[k3zrf]

Hey Skip nice switching arrangement. What is the value of those RF chokes strapped to ground?

[aafradio]

Those look like they would be exactly what I need, except my switches are indexed at 36° per step and the closest thing they list is 35° per stroke. They mention something about building a special unit to order with custom stroke angle, but I suspect that would be way out of my price range. The 35° ones are close, but 1° error per step would accumulate too much error over 5 steps for the switch contacts to line up properly.

Agree.  There would need to be a careful balance of detent spring pressure and solenoid power to work properly, as the last 1° should easily be taken up by the detent mechanism.  The solenoid will then simply reset for the next step.  I didn't mention it before, but you also have to have a switch section in the mix that will be the inverse of the selector switch in your shack so that when the switch gets around to the correct position the solenoid stops energizing.

The round part of the ceramic wafers are actually 4" in diameter.  The 5" figure includes "ears" or protrusions on each side of the wafer, making it more like an oval shape, to accommodate the mounting hardware. With the spring removed from the detent cam, the switches rotate with very little torque. With the spring engaged, it takes considerable torque, but I haven't attempted to measure it.

A cheap fishing scale on a lever arm should allow you to measure the torque with several different spring pressures to see whether it's within the published capabilities of the solenoid.

I have several 12 vdc reversible gear motors that turn at about 1 rpm.  The torque is great enough that I can't stop it from turning by hand.  The problem is figuring out how to make it stop exactly for each switch position.

Exactly!  A servo system can be designed to do it very precisely (there is a lot of CNC machining equipment out in the marketplace that do this) but the feedback loop with a position sensor is an added complication for something that should be fairly simple.  If you have access to a machine shop, I think it would be fairly easy to cut out an escapement wheel with ten sawtooth positions and then use a linear solenoid with whatever stroke is needed for the radius of the wheel.  Larger radius = less force required, but longer stroke, of course.  I think that's how I'd approach it, but I have a pretty complete machine shop in the outbuilding.  Anyway, it's something to think about....

[KD6VXI]

What about setting the switch so the solenoid is 'spot on' at slot #3.  Then you'd only be out a degree / maybe two at each extreme....

Just a thought...  Might make the 35 degree actuators usable in the 36 degree switches.


SR71s still fly out of Edwards rarely.  Usually at night, they have a telltale VERY distinct sound.

Then they fly around in circles waiting to be fueled.  What's REALLY cool is when you hear a plane, and a half minute later, you look up and see 'donuts on a rope' going across the sky.

--Shane