Instrument - DCS Mig-21Bis AOA Indicator

For a very long time have i wanted to build a physical cockpit. Unfortunately I am lacking the space to bring this project to fruition but atleast I can tinker around and build something.

And so I’ve decided to start working on this. A few months ago I started with drawings and plans of all sorts, and I’ve finally picked it up again. The first image is the AOA indicated from the 21 that I will be fashioning. Probably from a geared servo, that should be sufficient and fast enough.

The CAD drawing I made, for those interested:

So yeah, consider this my motivational topic too ;). Hopefully I can get this finished within a reasonable amount of time and perhaps even inspire someone else!


Wow…that is cool. I wouldn’t even begin to know where to start. I assume you snag some output data from DCS, output it through a cable to something that converts it to an electrical signal that sends the right stuff to the instrument?

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Thats is where you are wrong @BeachAV8R, It just magic. Pure and simple.


That is the standard answer on systems questions during our FAA oral - P.F.M.

Yes indeed, I’ve done some experiments before using DCS-BIOS, which is a framework build on top of the functionality provided by Export.lua.

I’ve both used it with a simple microcomputer called Arduino, or a Raspberry Pi. I kinda like the latter one since it supports my favourite language, Python. Another advantage of the Pi is, is that it works over the network with UDP. So hooking up extra mini-computers to listen in is easy. With instruments this is fine since they are mostly on the receiving end of data.

I’ve been toying around a bit on how to do the signals in the backend, probably some 12F625 or 16F* chip on the backend that I can use to also drive PWM for the LED lightning. That save me from generating and isolating a clock line. I can just send a discreet code for the PWM time and be done with it.

On the other hand, an 12C system would allow me to talk to each chip individually, is widely available and relatively cheap. But really, I don’t feel like making a whole framework of wiring on the back. Right now I will probably stick a cheap clone arduino on the back and be done with, directly plugging it in the USB.


great project - please keep us up to date on your progress, i’d like one of these myself :smiley:

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Hey…YOU just became my new best friend! :smiley:

I’ve been wondering if it is possible to use Python to make land based arresting cables in X-Plane. This guy apparently did it way back in 2006 for X-Plane, but the files can no longer be found, and his last post was in 2007 - so he has disappeared (scroll down to “redcooper’s” post):

I have no knowledge of Python - other than that it has been used successfully in X-Plane to do things such as sling loading and air-drops such as this one I did with a C-17:

For my NOLF concept for KMUD I was hoping to put cables across the carrier box pattern and then (it would require Python) somehow make the cables active (not animated…just working to grab the aircraft like the Nimitz does in X-Plane)…

Now, I know real NOLFs don’t have cables for trapping, they are just doing bounce and gos, but I’d love to be able to trap on an airfield. That same author apparently made an IFLOLS “ball” as well…but it was for X-Plane 8.4 and when I tried using the plug-in for X-Plane 10 it doesn’t show up in the sim.

Of course, I didn’t know how to design scenery either…so I might just decide to roll up my sleeves and learn Python. Oh dear…

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Well, I don’t have X-plane 10 yet myself, I plan on getting it somewhere in the near future. But perhaps it’s possible, I can imagine having to create some sort of vector going in the opposite direction to create the spring-y feeling of an arrestor cable. I wonder if that information is in the Python API.

Hoorah! Progress pics!

Although I prepared these bit earlier…

Mudspike mug for scale ;). This will be a backplate and the acryllic light diffuser and spacer plate(Its multifunction?!! Wow!). I just wish I had some better tools at home at this point. Oh well, that’s what you get when people put pressure on a drill…

In case anyone is wondering, the space between the drill holes, the space that is closer to the corner that now looks vacantly open will be for mounting holes once I decide on how to go about that. I could either build it all on rail systems with a few hinges(hoorah, compact!) Or mount it in a nice wooden frame for permament use.


Now then, onto the electrical work. In theory, all that I need is a little board that has a standard 5V(or, 3.3V, whatever. really) output and some sort of movable surface. Servo’s a nice and cheap, but noisy. Aircore motors are cool but hard to get, although the aircore and steppemotors used in dashboards are easier to get these days, and relatively cheap.

Each and everyone of those have their own disadvantages. A servo uses a PWM, Pulse Width Modulation. What this means is that it has a little cheap that measures how long the pulse over a width is high. The width is usually 20ms, and within that width the HIGH time determines a position. This is a quick system that is easy to use, widely available and relatively accurate. Unfortunately the rotation is limited, usually to 180 degree. You can off course sacrifice accurate for range with gears, which is what I will do for this gauge.

Steppe motors are neat, they use a pulse coming in over 2 different lines(the simple ones) to rotate by 1 step. This step usually has a rotation distance associated with it, for example 0.8 degree per pulse. If you hook this system up with a reference point then you’ve got a pretty accurate system. Although very fast rotations can throw it off over time. Useful, but a bit trickier.

Aircores are also really cool. They do not have a lot of torque, they do have the highest speed and accuracy though(if properly calibrated). Aircore consists of 2 coils, both creating a magnetic field that is 90 degree offset. This will then rotate a magnet that is attached to the indicator axis. This magnet will try and find the balance point between it’s own field and that of the 2 coils. Magnets! Waddayagonnadoaboutiteeeh?!

Anyway. All I really need is this:

The Arduino is broken but consider it an illustrative example. I can simply hook up servo, and funnel the DCS-BIOS data straight through the arduino to the servo! How cool is that?! REALLY COOL!

I also figured that I would show the methods and technique’s I’ve used to create this once I have the AOA gauge done. perhaps one of you all would like to give it a go? :wink:


Oh no, Dad has just bought himself an Arduino Kit. I may have to liberate it and make my own setup now…



For those that don’t know, Microchip is an actual manufacturer and not the name for a IC(Integrated Chip) package. The name is as generic as can be, but C’est la Vie in the great words of the late Robespierre, fervent supporter of the MiG-21Bis as is well known.

Anyway, I have this fine programmer, it does what it needs to do but its a clone. What programmers do is upload the code to those little black chips you see everywhere.

The grey box connects to the computer, gets a hex file from a IDE(where people write code), and sends it to the chip. The green box on top of it is a easy way to upload it to the chip. In this case the venerable PIC12F series from Microchip.
As luck would have it I cannot get this grey box to talk with MPLab(X) anymore. Last time I got it working was in 2012 and thus I wasn’t in the mood to hunt for a specific driver combination. In this case I opted to go for the Atmel AT chipset architecture. These days owned by Microchip so yeah, i loose out on any price advantage.

Long story short, I got a new programmer!

It’s a Pocket AVR Programmer sold by Sparkfun. Quite a nifty little device, and because the Arduino uses the same chipset I can use it to change(or remove) the bootloader and get some extra space! Unfortunately I do not have any chips to program with it yet, that’ll have to wait until tomorrow I fear.

Short little update for today. I ordered a whole bunch of parts so hopefully I’ve got something to show for it in the near future!


Schematic, pls

Once I got it all worked out I will publish all the schematics, material lists, etc. Just let me make sure i am not creating some bug-riddled mess first :wink:

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This is the area of witchcraft. How many goats will be harmed in the making of the AoA?:grin:

I always admire those who can do this. Good luck and looking forward to seeing how it pans out


Alright,. Found cheapo instrument steppe motors so I’m using those for the instruments with a small range, looks very easy to use!

4 wires and a arduino makes a nice hackjob!

All the code I’m using currently grabbed from here:

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