Need bipolar (-5v...+5v) output to interface to vintage Frasca sim

[jph]

Nice, from the time that the right to repair was still honored

So true -

[jph]

Hi Brian, can you post a bit more of the second page with the synchro / resolver details ?

I simply cannot believe what you got for such a small amount of money.. amazing !.

It all looks straight forward enough, but have you considered using the actual digital inputs and leaving all the dac / drivers and voltage converter cards in place ?

Do you actually have details to the digital inputs to the card rack ? . I would be VERY tempted to look at this. I am sure it is all appropriately buffered and will use off the shelf components that are still available. probably stacks of 741 op amps or similar and cmos logic lol

I would definitely be prone to go that route but I was brought up on that stuff.. that way, you only have to supply the digital inputs. (for the majority). It was probably hooked up to a 'mini' frame with a rack of rs232 outputs and unix.. (true 232 +/- not the 5v version - ) so may well be easy to replicate. does the manual have any details of the digital driver circuits ?
It was common practice then to have a 'mini' frame with a mass of 232 outputs and terminals. I would guess this would use a similar scheme. driving true 232 levels is easy from a normal digital output.
We used to have the unix minis with a 50 set 232 output box on the rear for 50 terminals at the Ambulance service control system that I managed then, and that was in the 90's !!!!!! - and that was only the non emergency side..... yikes ...

it would be really easy to service if you had the maps (schematics) also. I doubt there is anything on the card rack that couldn't be replaced today.
Joe

[brianbarr]

I will post more pics of the maint manual later this weekend.

The DAC/ADC/"Bitboard in and out" chassis is the big box in the picture that shows the rear of the rig. From what I can tell, the DAC, etc communicates to a large "processor chassis" in the "IOS" or instructor operator station that is in a separate desk and cabinet. I have not analyzed the IOS portion of this rig in depth, but this IOS box is where the i386 processor that runs the control logic is located. The IOS software loads from EEPROM and talks to the DAC, etc chassis over some sort of serial interface or interface(s). I guessing I would have to reverse engineer that serial protocol to reuse the DAC, etc chassis as you suggested. The visual graphics system is another standard desktop PC of some kind that drives a small vga display with the fresnel lens bolted on the front of the fiberglass enclosure. Frasca is still very much in business (they make every kind of simulator you might imagine, such as full motion B737 stuff ) and maybe I could coax some friendly engineering type to let loose with some vintage docs for a hobby project. Don't know yet. The manufacture date of the majority of this stuff is 1988. The digital control stuff here I think is probably reasonable accurate, the visual display subsystem extremely primitive but the hardware and analog stuff is extremely well engineered and documented. The actual "flight model" logic I can't imagine is very sophisticated. To change airplanes there appears to be largish parameter files that you load into the control subsystem. There are pages and pages of parameters with many penciled notes in the docs. More to discover. I was told this rig was actually working as a teaching aid up until about 9 months ago when something happened to the IOS chassis involving a stray bolt that worked loose and fell into the IOS card chassis and zapped something important. That it was still working as designed in 2019 is amazing. It was not worth repairing to the (secondary) school that was disposing of it and they were installing small desktop redbird systems and needed the room. This thing is huge and I happened to have a heated garage and some space I can make for it -- and I was lucky that it was located in an out of the way place (at the KPLN airport) so no one else in the area was interested. An interesting back story to this project is that this Frasca sim was originally installed at a part 141 flight school in N. Michigan where I did my initial flight training (at KTVC) way back in 1979/80. The chief flight instructor at the school was my instructor for my private pilot rating .. and his name is all over the service documents I received for this thing. Full circle !

[brianbarr]

So I took a flyer and called Frasca customer support down in Urbana, IL.. spoke to a very helpful guy named Jason..

We chatted on what I had and he answered a few questions..

They still support this 30+ year old machine. When I furnish him the serial number of the rig he can be more helpful (that info is buried in the docs somewhere and I am out of town until tomorrow) .. Frasca still has replacement boards for this thing and can do component level repairs on the boards (for a fee of course..). Jason was curious if I was interested in bringing it up to modern standards with a new computer and new graphics display subsystems, and such an effort would be in his words "a sizable investment.." yes I can imagine what that would run..

Per Jason, the DAC/ADC/BITBOARD chassis in my vintage of sim talks to the main IOS controller via a serial protocol and I was led to believe that docs on said protocol might be available. If I can get my hands on more docs I may be able to just run with the existing DAC/ACD/BITBOARD chassis and implement a protocol driver with messageport in Air Manager or on a raspberry pi.
Back in 1988, the max a serial port ran was generally 9600bps or maybe 19,200bps. A 2400bps modem was state of the art. That would be a pretty slow update rate over one serial interface so maybe there are several serial interfaces at work here.

Another benefit of getting my hands on the serial protocol is that the whole simulated bendix/king avionics stack in there would be usable more or less unaltered. All the simulated avionics are on some kind of a parallel bus with a ribbon cable connecting them all to the DAC/ADC/BITBOARD chassis.

An "available" updated card in the chassis features ethernet (prob 10mpbs over coax or somesuch) .. and I may be able to get my hands on such an upgrade, but what protocol might it talk? Novell IPX/SPX ? TCP/IP was not ubiquitous back in the early 90s.. How far we have come.

More to follow on this. A lot to digest.

I might fly my airplane down to Frasca Field near Urbana IL where Frasca is located and pay them a visit. That would be quite interesting.

BTW it seems there is a cotttage industry in buying up older Frasca sims and redoing them with modern compute engines. An overhauled and updated sim runs $40k !

The Frasca sim hardware is very well done and I can see these things easily redone with a second life.

[Ralph]

I spoke to someone last year at AirVenture. He knew about a warehouse in Texas full of these simulators. He was thinking of buying them all and then update them. I'm not sure if he went through with it.

[jph]

I spoke to someone last year at AirVenture. He knew about a warehouse in Texas full of these simulators. He was thinking of buying them all and then update them. I'm not sure if he went through with it.

Hi Ralph, can you PM me with details if you still have them ? cheers, Joe

[jph]

So I took a flyer and called Frasca customer support down in Urbana, IL.. spoke to a very helpful guy named Jason..

We chatted on what I had and he answered a few questions..

They still support this 30+ year old machine. When I furnish him the serial number of the rig he can be more helpful (that info is buried in the docs somewhere and I am out of town until tomorrow) .. Frasca still has replacement boards for this thing and can do component level repairs on the boards (for a fee of course..). Jason was curious if I was interested in bringing it up to modern standards with a new computer and new graphics display subsystems, and such an effort would be in his words "a sizable investment.." yes I can imagine what that would run..

Per Jason, the DAC/ADC/BITBOARD chassis in my vintage of sim talks to the main IOS controller via a serial protocol and I was led to believe that docs on said protocol might be available. If I can get my hands on more docs I may be able to just run with the existing DAC/ACD/BITBOARD chassis and implement a protocol driver with messageport in Air Manager or on a raspberry pi.
Back in 1988, the max a serial port ran was generally 9600bps or maybe 19,200bps. A 2400bps modem was state of the art. That would be a pretty slow update rate over one serial interface so maybe there are several serial interfaces at work here.

Another benefit of getting my hands on the serial protocol is that the whole simulated bendix/king avionics stack in there would be usable more or less unaltered. All the simulated avionics are on some kind of a parallel bus with a ribbon cable connecting them all to the DAC/ADC/BITBOARD chassis.

An "available" updated card in the chassis features ethernet (prob 10mpbs over coax or somesuch) .. and I may be able to get my hands on such an upgrade, but what protocol might it talk? Novell IPX/SPX ? TCP/IP was not ubiquitous back in the early 90s.. How far we have come.

More to follow on this. A lot to digest.

I might fly my airplane down to Frasca Field near Urbana IL where Frasca is located and pay them a visit. That would be quite interesting.

BTW it seems there is a cotttage industry in buying up older Frasca sims and redoing them with modern compute engines. An overhauled and updated sim runs $40k !

The Frasca sim hardware is very well done and I can see these things easily redone with a second life.

Hi Brian,
Nice move, well worth it.I needed info on a twotter (twin otter) and ended up calling the company direct ... excellent response but it all depends on who you get ......
I would avoid the 'network. version like the plague as you rightly say, depending on WHEN it was released, it will probably be Novell ipx/spx - yikes - ... and probably over 10base2 with tees and terminators ...yikes again .. the serial is far FAR better. I also think you 'may' be very surprised at the actual speeds of the serial comms at that time. The common V.XX protocols were all designed for POTTS.... not specifically for point to point short distance. Speeds available - especially custom speeds could be quite high. Take MIDI for example - high speed, 16 channels !!! and developed a considerable time before the sim you have. It should be relatively easy to fix the 386 board providing you have a map and an idea of input and output states. I used to fix commodore PETS / 64 / data General etc as a sideline and they were really simple when you could see what they had done. Has the 386 got the appropriate 387 co-pro on the board as well ? - just wondered - it gives you an idea as to complexity..... The maps for that and any fault finding / scope data and voltage test points -are a gold mine, and a simple logic probe of course .... that should be all available.
From what you are saying I would really go the route of stuffing the appropriate serial data into it. I think you may be surprised at the result. It would save a HUGE amount of work.
Have no fear / doubt at all over 'old' (which is a relative term at my age haha) hardware as it is far far easier to maintain than modern throw away stuff and repairing at board level is usually relatively simple.
As an example, our 'yott' had a 1976 vintage autopilot that is still going - as far as I know - today and when we had the boat for 10 years, I wouldnt have changed it for anything. it was bombproof. Instead of using a fluxgate 'compass' it used a REAL compass with 2 Polaroid opposed polarisation discs and optical sensors - the more the disks overlapped the less light transmission.. amazing simple and again, bullet proof. the main control unit was analog and i had full maps for that with all test date - never had to use it though even though it was often exposed to weather in certain sea conditions. the motor drive for the rudder would have turned turret on a sherman tank... anyway, I digress... I think that is definitely the way to go. I am happy to help where I can, I am sure others here are also. you dont want to re-invent a perfectly round wheel that only needs some 'where to go / what to do' inputs - Think about the force feedback for example ? - much easier to enter a few bits (well bytes lol) of data and let the system do it all for you than programming complete algorithms from scratch.
I love this project, you are so lucky.
Joe

[Ralph]

I don't remember who it was and he didn't mention any names.

[brianbarr]

After some more extensive research on the oddball sin/cos gauges -

https://www.youtube.com/watch?v=emA93hcDrgg

I have found out they are not so oddball after all.

This technology was used extensively in the automotive world back in the 80s and 90s and was generically called “air core” and there are driver ICs that can do most of the messy bipolar work for you.

PWM does not mix well with driving these things as I have discovered:

https://electronics.stackexchange.com/q ... core-motor

The driver chips are generally obsolete, but I have found a source for the CS4122 in china on ebay and have ordered 6 chips (free shipping !) for a test board.

The CS4122 has a SPI interface …should be pretty easy to interface to with a pi or arduino — most of the other driver chips take a pulsed “tach” input

https://www.youtube.com/watch?v=K1krpXF ... gs=pl%2Cwn

CS4122-D (2).PDF

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CS4121-D.PDF

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CS8190-D.PDF

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SA5775_PhilipsSemiconductors.pdf

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[Ralph]

Well done research! You can use SPI on the Arduino with our message port library.