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Post by Ron Walker on Sept 9, 2022 13:33:01 GMT -7
Posted by: Ron Walker Apr 12 2013, 08:14 PM Just didn't want to take the chance of knocking the bottle over into the electronics.
So many things do come to mind and again the word "compromise" rears its ugly head. I basically picked the angle so that I could easily read and reach any component on the three sides. I also wanted to be able to squeak in two people if that ever became necessary. I will probably need the readouts to be a bit brighter so I can read them (at least until I'm really proficient at the knobs and switches) and I don't want a lot of light showing on the dome. I even plan to have a little overhang of the top plate to help stop any light going upward. Also, as the control panel gets flatter, it would have to get thicker because of the various components attached to it.
As you said, my head will be in the stars and I should be able to see most if not all of the audience. But, do I really want to have eye contact with the audience. All those people looking at me is not so "funner" for me. The first experiment will probably place the chairs in one large circle and see how that turns out. Since they are individual, they can be placed in almost any configuration.
My original plan was to have the control desk moveable but I'm thinking that it might cause more problems then it will solve. The plan was always to have it in a north-east direction. That way it is very easy to see the entire ecliptic as well as the north circumpolar constellations. I have the feeling that a lot of other equipment will accumulate around the control console. Certainly the audio equipment as well as the mirror dome projection apparatus, then there's the laser show machine as well as the orrery and the other multitude of devices that will accumulate. Also, once I add the banks of transformers to the base of the control unit, the wheels will go flat. There will probably also be several cable bundles that will not enjoy a lot of flexing so the control console will probably become fixed.
It will stay on wheels until the dome is finished so it will be easier to move out of the way. This part will indeed be funner!
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Post by Ron Walker on Sept 9, 2022 13:36:31 GMT -7
Posted by: Ron Walker Sep 10 2013, 06:24 PM Not at all sure if I should start another topic for this but I guess this is a good a place as any. The heat finally broke today as a major system of storms have come through. While it was rain off and on today it was very much like a typical Chicago day, at least as I remember them. Temperature 75 degrees with a humidity of 80%. Not quite what I would call ditch digging weather so I decided to start some of the preliminary reconstruction work on the planetarium itself. While I know there is a lot of work yet to do on the building itself, I just have to start on the projector a little. After suffering through a rather nasty flu/cold the last couple of weeks, I am reminded that no one lasts forever and I would certainly like to play with this a little before I can't play at all any more. So, since I have found that I am having a hard time doing things like sheet rock by myself, I'm thinking of holding off until some help is available later in the fall. However I need to continue so I'm thinking of starting the wiring to the projector core and get that part of the project moving along. My plan includes building a substantial protective box that can be set up around any parts of the machine that wind up under the dome before it is finished. The first step is to put in the basic wiring which consists of about a mile of individual wire circuits. I actually put in two 3 1/2 inch conduits so I would have a spare to add more circuits if the need should arise. After a substantial amount of pushing and pulling and sliding and sweating, I managed to push 142 wire runs through one of the pipes. Obviously several of these cable runs are multiple singles in a large jacket, but that just makes them larger and more difficult to pull and push through the conduit. I also cut down the conduit as there are mechanical parts of the projector mounted quite low because of the limitations on my building height. The projector itself will probably use only about 100 or so and the extra are for whatever I need them for. Knowing me, I will need them. At the other end the cables just pour out of the conduit. At first I was just going to have them go into the control console but now I'm thinking a short rack mount cage might be best. I have a tall one and might just cut it down to three or four feet.
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Post by Ron Walker on Sept 9, 2022 17:37:30 GMT -7
Posted by: Ron Walker Sep 21 2013, 02:01 PM I have been spending some of my "off" summer time going over the wiring that originally existed for this projector. Certainly for myself and partly to understand some of the JHE changes on Mr. Brent's machine. As I said over on his thread, there is a basic deign for a control circuit that is used and multiplied on each PCB. The nice thing about simplicity is that it usually tends to work best and the longest. Mr. Brent's machine is still basically the original Viewlex electronics with the JHE materials added (I believe) to run slide projectors. On my machine, the entire control circuits were replaced as they had been nothing but trouble from day one with the original Viewlex boards. Once this 100 hour conversion was accomplished, the projector ran fine from then on. My thought now is to try and understand exactly how these various boards and electronics work and perhaps continue the use on some of the circuits. Time will tell as I continue to experiment. As an example here was one of the new control boards that was screwed to the wall in the control closet. This board is designed to run 16 separate functions. On the top left is the power transformer and power supply to run the various circuits on this panel. Top center and right are two comparator boards and a plug to the main control panel. Through the center are four sets of four SCR's that do the actual dimming and then along the bottom are the tie strips for the various circuits out to the projector. A second panel contains all of the high current SCR's for loads like the star lamps. Again across the top are the power supply for this board and an eight channel comparator which runs the eight SCR's below. You will note (especially to the right) the very large heat sinks for the high current loads. Again, the strip at the bottom is for projector connection. If anyone knows off the top of their heads exactly how the comparator boards work it would be appreciated. I know they are used for computer control but was wondering is they add any automation while the machine is in manual mode? If no one knows, I will eventually experiment around and hopefully get an understanding of their operation and report back.
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Post by Ron Walker on Sept 9, 2022 17:41:14 GMT -7
Posted by: Ron Walker Sep 21 2013, 02:36 PM For the life of me, I couldn't remember what was used for power for the various motor circuits. Originally Viewlex used a + and - 100v DC supply that controlled the motor via one of the many PCB's in the original control cabinet. That cabinet was totally decommissioned so the system had to be handled in another manner. The original control had a center stop position on a control pot. Left for reverse and right for forward. Since the control remained the same but the various circuit boards are gone forever, a new system needed to be designed to run the motors. What follows is conjuncture but I believe it hits close to the mark. There were at least a dozen small relays double sided tapped to various nick and crannies both in the control console as well as the control closet. I noted that each of the control pots had a micro-switch that switched at the pot's center position. My assumption is that the switch was used to reverse the polarity of the DC to the projector and thus change direction of the motor. All well and good, but where was the DC power supply for all of this. I did find this plate with four transformers on them as well as a four SCR PCB. So how exactly did this all work? I must say I'm guessing once again but I believe the control pot is center tapped (I need to check that) and will control the SCR when turned in either direction. The SCR will power one of the transformers on the board. The micro-switch will reverse the polarity of the DC motor via one of the many relays mounted about. But where is the AC converted to DC. There are some filter capacitors on the board but none of them are connected. They actually aren't really needed as a DC motor does not require filtered DC to operate well. Now wait, what are those globs of tape on the output wires from the various transformers? Let's open one up and see. Ah, a full wave rectifier for converting AC to DC. Mystery solved! I don't think I've ever seen one of these mounted quite like this before, but if it works...
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Post by Ron Walker on Sept 9, 2022 17:41:50 GMT -7
Posted by: Ron Walker Sep 21 2013, 05:38 PM Did a little research and what I've been calling an SCR is in reality a TRIAC. That really makes more sense as a TRIAC is designed for controlling AC voltages which most of the projector runs on. There is also an optical isolator in the circuit so that the control circuit and voltage never come in contact with the main controlled voltage...nice. If the TRIAC should ever short out, high voltage will never contact the control circuitry.
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Post by Ron Walker on Sept 9, 2022 17:42:44 GMT -7
Posted by: albert Sep 22 2013, 05:24 AM
Hi Ron, I greatly sympathize with you scratching your head in front of all these control circuits. Perhaps it would help to study control circuitry for Radio control models. I remember something called a "bridge" circuit which permitted you to run a dc motor forward and backward. Nowadays its all electronic switching, but I grew up with DC motors....Do you think your motors had some kind of feedback mechanism to tell the electronics how fast they were going? A "tacho generator" attached to the main drive shaft perhaps?I guess the control pots were attached to circuits so that different positions would generate a pulse width modulated signal. From then on one could determine what pulse lengths would be " forward" or backward".Perhaps there was also a set of switches attached to the pots, around the center point, and these would switch relays in the motor line to reverse the motors direction.Just my 2 cents.My old Zeiss has a wire wound double potentiometer controlling the motor in a "Barkhausen bridge" setup. Dont ask me how it works, I will dig out the schematics if I can find them. It works perfectly without any relays or other electronics, but of course the pot gets mighty hot at low speeds of the motor.I recently saw a planetarium that is being built around another old Zeiss ZKP 1. They are redoing the entire control system and run everything off a computer, doing all the circuits themselves. Gave me a complex! I will try and post some pictures soon, they also made a wooden dome. They had to redo all the wiring inside the projector....
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Post by Ron Walker on Sept 9, 2022 17:43:31 GMT -7
Posted by: Ron Walker Sep 22 2013, 12:20 PM
Hi Albert, As I mentioned before, each of the motor drive pots has a micro-switch mounted at center rotation. Thus a simple way of reversing direction.
My original plan (and might still be) is to replace everything with new control electronics. Then I thought it might be nice to have some automation such as automatic dimming of the house lights over a certain period of time. I'm not at all sure that a computer would be required for that sort of thing, probably just some kind of timing circuit. Again I could start from scratch but why not see if any of the existing materials can be used. The problem is that without some kind of schematic, everything needs to be reversed engineered so to speak to see what is really going on. Also, things can't be taken at face value. Some of the boards are marked "SCR board" leading me to believe they were actual SCR's. Now a SCR is designed to work with DC or 1/2 the AC wave form which is fine but not for a lot of these loads. Thank God for the web, as I was able to read the part numbers of of the various parts and find out what they really are. Thus I found out that the SCR's on the SCR boards are really TRIAC's which are basically an SCR for AC current. That makes a lot more sense for the operation of the system. The process is slow.
As to the motor drives. They are simple two wire DC motors that reverse when the polarity of the input changes. I'm thinking that your pot is more like a rheostat in that the slower the motor the more of the drive current needs to be dissipated by the control. My simple fix to this is using an auto-transformer or Variac, the output of witch is run through a full wave rectifier, the a reversing switch, and then to the motor. With this simple system (and with no heat at either the Variac or the motor) the diurnal in the Minolta projector will run a day from 2 to 60 minutes, a tremendous amount of control. There are no feedback winding's on any of the motors but there are Selsyn drives to run positional readouts on the control console. I believe the original circuitry used these units to lock the annular drive to the diurnal motion but all of this circuitry is long gone. I am thinking of using some simple step down transformer to run the annular drive off of the diurnal power for interlock. I just have to see at what voltage and thus what speed the mechanical inertia is overcome.
If you are uncomfortable with the heat buildup in your control, you might consider replacement with a Variac.
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Post by Ron Walker on Sept 9, 2022 17:44:22 GMT -7
Posted by: albert Sep 22 2013, 11:51 PM Hi Ron,reverse engineering these existing boards is quite a chore if you do not have any of the original schematics. That might be indeed a slow process!We are thinking about integrating the Zeiss controls with a DMX driven lighting console. This way one does not have a windows based computer on board - I do not trust them too much on the stage or in a theater. I believe that the main difficulty for a live show is coordinating the various lights- house lights, cove light in various colors- with the functions from the projector. If there is automation on the lighting side, with slow ramps and long fade times -try to do a two minute fade by hand!- then the projector can still be run all manually. In my case I hope to find a way to switch the sun, moon and planet lights separately although I do not have sufficient sliding contacts. Will have to be some kind of wireless control. Or a multiplexer approach with the signal on the power line, nut that will have scratching and noise due to the sliding contact. Of course you are right, my "pot" is a rheostat, but it varies the current thru the stator winding of the motor as well as the current thru the rotor. This way you get very slow speeds and the motor will not ratchet or hum and lose all its torque. I have not been to the bottom of this yet...
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Post by Ron Walker on Sept 9, 2022 17:44:44 GMT -7
Posted by: moonmagic Sep 24 2013, 01:22 PM Just a note to say this part of the peanut gallery is still following along, although I'm really in over my head just trying to follow along. With that said however, NOW this is beginning to look like a REAL planetarium project. All those many wires of every color and size spewing forth from conduit up from the floor. Ah, ha...that's a planetarium for sure! mm
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Post by Ron Walker on Sept 9, 2022 17:45:15 GMT -7
Posted by: moonmagic Oct 16 2013, 11:45 AM WHERE DID EVERYBODY GO?
Ron no posts in 3 weeks?
Gare no posts in a month?
"moon-base one calling..."
mm
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Post by Ron Walker on Sept 9, 2022 17:45:54 GMT -7
Posted by: Ron Walker Oct 16 2013, 10:14 PM
Still alive. Just a bunch of things happening at once. I will explain in more detail later.
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Post by Ron Walker on Sept 9, 2022 17:46:26 GMT -7
Posted by: moonmagic Oct 17 2013, 12:07 PM glad to know you are ok. Been missing my fix of encouragement from the "domes are us" world. mm
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Post by Ron Walker on Sept 9, 2022 17:58:40 GMT -7
Posted by: Ron Walker Mar 5 2014, 09:32 PM I haven't been here for a while as I have been preoccupied with building the dome. It is now time to rebuild this fantastic machine so first it must be moved in an reassembled. The base was moved in some time ago as were the main set of wires pulled through the underground pipe. But now it is time to bring in the major components of the projector. I placed the central core on the support legs when I placed the unit into storage waiting for its resurrection. Now it is time and the unit is moved to the stage door. Vince has a nice low trailer (Vince has everything) that was about the same height as the stage floor. With a large flat aluminum plate (Vince had that as well) the gap was easily covered and the core moved to the trailer. While not going far, Vince ties the core to the trailer. No use taking any chances now. Actually as I look at this picture, it is taking the rope off of the machine as we have already backed up between the OB and the horses. We are actually at the north door of the dome.
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Post by Ron Walker on Sept 9, 2022 18:01:58 GMT -7
Posted by: Ron Walker Mar 5 2014, 09:42 PM Soon we are off on our 200 ft trip to the new dome. Julie suggested that we use the north door as it required less backing up. This was the same way the concrete truck came for the second half of the foundation pour. We then use the engine crane to lift the core off of the trailer and onto the ground.
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Post by Ron Walker on Sept 9, 2022 18:05:56 GMT -7
Posted by: Ron Walker Mar 5 2014, 09:50 PM Once back on the small dolly, the central core is moved into its new home. All of this before lunch. Afterwards Julie and I decided to try and mount the central core onto the projectors base. Boy, that was easier then I thought, dare we mount a planet cage? We have time and we should really balance the load on the central core.
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