Digital-To-Synchro converter for interfacing real aircraft indicators

Hi,

I wrote a long post as a reply to a question about my upcoming DTS-converter in my B256A13-thread. I had intended for it to be a short post and let it be in the B256A13-thread, but it grew so big that I decided to create my DTS-thread now and put it here.

As the text was written as a reply to someone who already knew what the board is, it is not a good introduction! However, I do not have the time to re-write it now, so here it goes:

I will solder the first unit tomorrow. When I have one ready, I will start adapting the firmware from the earlier prototypes to these new boards. And I will have to create a USB bootloader, because the prototypes I developed didn't have one. Then I will send this whole first batch to customers here in Sweden to let them test it out and help me improve things like documentation, PC-side software and so on. I believe I will have ordered the second batch in 4-5 weeks. Work isn't taking up all my spare time right now, so I really believe I will be able to stick to that timeframe.

About interfacing with DCS. I have already developed an IOCP-client that makes the board compatible with SIOC. It should also be a simple task for someone to write an IOCP-server in Lua to be able to communicate with the boards without SIOC. I won't be that someone though, so that will only happen if any of the DCS customers feel creative. The other thing I will release is a C++ library to interface directly to the boards.

Remember that the indicators that can be controlled by this board vary greatly in design. You will have to know how your particular indicator is interfaced to be able to decide if this board will do the trick. A lot of the synchro-servo indicators are not having internal amplifiers like the ARU-2B/A, and will need more than just this board to run. Also remember that you will need a 26 Vac, 400 Hz power supply to run this board and most of these indicators. The ARU-2B/A will need 115 Vac, 400 Hz, so you will need both 115 Vac for the ADI and 26 Vac for the board. And they need to come from the same power supply so they have the same phase. If you only have 115 Vac on your 400 Hz power supply, one resistor can be used to get 26 Vac to the board. More about that in the currently non-existent documentation.

The power supply for the board should be somewhere between +/- 21 Vdc and +/- 28 Vdc. That is right, you will need both positive and negative voltage. I have written +/- 22 Vdc as a recommendation on the PCB. The higher voltage you use, the hotter the amplifiers on the board will get. You may also be able to use a lower voltage power supply, like +/- 18 Vdc, but that depends on the type of indicator and is for the advanced user to figure out. If a lower voltage power supply is used, a trimmer on the board will have to be adjusted to lower the voltage of the DTS-output to avoid the output amplifiers from clipping the waveform.

As you see, this product is not for the complete electronics fool. Hooking up an indicator that someone else has already figured out how it should be wired to the board is not that hard. It is about 10 wires to hook up one board to one channel (pitch or roll) of the ARU-2B/A, and 8 more wires to hook up another board to the second channel. The hard part is figuring out how the indicator is to be wired to the board, and if the board will be able to run the indicator at all. For the ARU-2B/A, that job is already done. If you have another indicator, I may be able to help figuring out how to interface it if you can provide schematics or detailed photographs of the indicator internals.

As a side note. This board can also be used to create two AC-voltages of equal frequency and vary their amplitude individually from software. I don't know how common that is worldwide, but the Draken has a lot of indicators that is controlled in this way. My IOCP-client and C++-library will be able to run the board in this mode too.

Niclas

In a few months I plan on starting to interface my F-84F fuselage gauges. I might want to pick your brain for information soon.

In a few months I plan on starting to interface my F-84F fuselage gauges. I might want to pick your brain for information soon.

You're welcome! :)

This is a cool project, may bring a bunch of instruments to life.

cheers

Peter

This is a cool project, may bring a bunch of instruments to life.

 

cheers

 

Peter

I already know about 20 indicators here in Sweden in various Draken and Viggen simulators on museums and on NovelAir that will be brought to life by it. Just one Viggen simulator will require about 10 of these boards to run all the synchro-indicators unmodified. It is the number of interested people outside of Sweden that is the big unknown for me. Time will tell, and I'm excited about it :)

Is the price still in the $100 each range?

Is the pricea still in the $100 each range?

Yes, the price is 1000 SEK so it's more than $100. The USD is very weak now compared to what I was used to when growing up. Back then it was about 10 SEK for 1 USD, now it's about 6.5 SEK for 1 USD. The boards have some expensive components and will take about 2-3 hrs each to assemble and calibrate.

Have you found a good source for PSU's, they are not exactly the thing you find at your friendly corner store :)

Have you found a good source for PSU's, they are not exactly the thing you find at your friendly corner store :)

Unfortunately not. Maybe I'll build my own when (or if) I need to run an indicator like this at home. The museums that are going to buy my boards have got them from the air force.

Need some ADI's up and running? ;-)

Need some ADI's up and running? ;-)

Why yes, yes I do. :) (Or will.)

WoW.....

All boards from the first batch are now soldered, programmed and calibrated. I will order the second batch tomorrow.

AJS 37 Viggen 3-axis ADI running with three of my DTS-boards:

This cabling scetch might come in handy. I did this to keep track of cabling in our J-35 Draken Pit for the syncros (work ongoing). Demand was to have a modular setup so each main part can be separated.

Lot of cabling in the rack so it feels a bit more safe to be able to pull the power and have each part accessible with ease if (when) troubleshooting starts :-)

Cheers (and thanks Niclas)

Gus

might add also that it's no warranty attatched to the scetch.. theory is one thing but time will tell :-)

I don't have any of this stuff but this looks awesome! Nice work!

Strangely enough I had a dream last night I was allowed to raid an F-16 cockpit of all its electronics...... You guys are really getting in my brain!

Naaa, we got nothin to do with that.. the effect you experience comes from excessive use of sim forums... ;-)

(but if you ever find a cure, please let me know. Need one badly)

I wish I could find a static inverter for a reasonable price. :(

g.

I wish I could find a static inverter for a reasonable price. :(

 

g.

Gene, what input and output are you looking for? How "clean" does the output need to be?

I need 110VAC @ 400Hz. Because I'm feeding 2 real ADIs and an HSI, it needs to be as clean as possible.

tnx.

g.

Do you have a technical spec for the indicators Gene?

I've got the pinout for the primary ADI, but not the backup ADI & the HSI. The connector on the HSI needs to be replaced. It was "de-milled". :(

For the sake of saving money, I'm planning on driving them with synchro transmitters coupled to stepper motors.

g.

Are you sure they can be controlled by just a synchro transmitter or a DTS-board? I think that you may need special amplifier boards as well. The ADI in the A-10C and the AJ37 have these amplifier circuits built-in, so your primary ADI might have them too. Your HSI may also have them internally if you're lucky, the one in the A-10C does. Your standby attitude indicator will most probably not have them however. Is it a SAI from a simulator? If it is a real one it probably has it's own gyro and doesn't use synchros at all.

If you have the part designations then maybe it is possible to find a technical manual on the Internet?

Powell has some schematics for building your own 400 Hz inverter if I remember correctly. Shouldn't be too hard, just an oscillator and a pair of audio amplifiers in push-pull configuration to get up to 26 Vac. You will probably need a 26/115 Vac transformer as well, because the ADI/HSI might need 115 Vac.