Hi all,I'm building a generic two propellers cockpit (using FSBUS) so I found two instruments from a real wrecked aircraft: one is a virosbandometer and the other one is a gyroscope with VOR indicator.I tried to open the gyroscope and I found there are two motors: one moving the compass quadrant and the other moving the arrow of the VOR indicator, both motors are connected to a board.My question is: is it possible to use those two motors directly with FSBUS servo board or stepper board instead of replacing them with servo RC?The gyroscope is reporting the following labels:SLAVED DIRECTIONAL GYRO-RMIIG-830AAircraft Radio CorporationBoonton, New Jerseythe 2nd label reports:Part no. 289-1SSerial no. 370Type SLAVEDSpec. TSO C6cInput 4.5-5.2IN. HgOutput ARINCBest regards,Bob

Bob,It's possible but may be quite a bit more difficult/expensive than it is worth.The compass card is probably driven by a device called a synchro receiver. It looks like a motor with five wires going to it. Often they are labeled S1, S2, S3, R1 and R2. R1 and R2 connect to the rotor. The others connect to the stator. It is pretty common for these to run on 400 hertz power. If this is the type slaved unit you have you would need a digital to synchro ("DTS") converter and a source of 400 Hertz power. A commercial DTS costs a couple hundred dollars.Some slaved instruments used a device that combine a motor with a synchro transmitter. The synchro transmitter measures the position of the instrument's indicator and sends this information to the sensor the instrument is slaved to. The master instrument then sent power to the slave motor to position the slave indicator properly. Converting this style instrument to sim use would be a challenge. Mikewww.mikesflightdeck.com

Thank you Mike for your answer.Well...I've just opened the gyroscope to check what you wrote and... (of course) you were right !So now my challenge is to study the way to mount RC Servo motor to move the compass and the indicator arrow.Then I have another question about that: (if you know how FSBUS servo card works)Do I need a specific servo motor?and....let's suppose that the servo card and the servo motor to move the compass are connected...is the rotation of the servo motor already adjusted to "copy" the same rotation of the one displayed on FS, or I need some kind of a specific gear reduction or setting to adjust the rotation of the servo motor? I hope I was clear.It's not so clear (yet) to me how the servo card works and how to convert real aviation instrument to work with servo motors.I found some web site where there were pics about that "conversion" but there wasn't any kind of explanation on how to do it.Consider that I studied electronics and worked as TV,hi-fi repairing technician so you can feel free to use technical terms.Greetings,Bob

Bob,I'm not up to speed on FSBUS so I can't help you there, however, I have worked a bit with RC servos while building sim instruments. I don't think you'll be satisfied with an RC servo moving the compass card.RC servos have a rotational limit of typically 90 or 180 degrees depending on the specific model. Further, the servos have a dead zone designed into their internal feedback loop that results in the output shaft moving in discrete steps. The standard size Tower Hobbies servo I looked closely at seems to have about 250 steps for 180 degrees of rotation. If this servo were 1:2 geared to a compass card, the card would turn through 360 degrees but the step size would be a rather coarse 3 degrees per step.RC servos are controlled by a variable width pulse. My tests on the servo were done with a continuously variable pulse generator, so I am confident that the apparent step size is not an artifact of my test set up.The Tower Hobbies servo appears to be house labeled version of the standard size Futaba servo. It's a reasonable unit, but certainly there are more expensive models that may operate with smaller dead zones. The dead zone is necessary to stabilize the servo. Think of it as feedback compensation for backlash in the mechanical part of the servo loop.Even if you find a servo with an acceptably small dead zone, there is still the servo's inability to rotate past its internal stops. The servo uses a potentiometer for a position sensor, and that restricts the range of rotation.An alternative to an RC servo for the compass card is a stepping motor. a 400 step per revolution motor can be half stepped to provide 0.45 degree steps. A motor like this costs about US$5~7 http://www.allelectronics.com/cgi-bin/cate...T-46&type=store http://www.goldmine-elec-products.com/prod...aitem=5&mitem=5I don't know if FSBUS can drive stepping motors, but if not, it's not too hard to build a PIC based motor controller that can hang off a serial port. Here's a discription of a DG project that does just that: http://www.mikesflightdeck.com/Downloads/B...e%20Chapter.pdf Mikewww.mikesflightdeck.com

Thank you again Mike...I've just had a quick look at the PDF you linked but I found it very interesting...I will read it with more attention later.Fortunately FSBUS supports stepper motors so now I'm looking for information about that card to have a "wider" view of the whole "subject".Best regards,Bob