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Guest kdfossum

Servos HELP!

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Hi everyone,I'm putting my dual joke assembly together for my 744 cockpit I want them to be driven by servos, for feedback from A/P. I know this should be possible and I have a few questions regarding it.-What type of software do I use for feedback from FS9?-Is there a certain type of motor I would use, or could I use any old electric motor? I have motors from an old reel-to-reel (tape machine) I would like to use.-If I use them, can I have external power (not powered by computer)?The motors I have a pretty strong, I think they would be great if I could use them.Anyone have knowledge about this to give me some feedback on my questions?Best regards,

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Kevin,In real planes, the AP does not have any link to the yoke in the roll and pitch axis and rudder pedals for the yaw axis. The AP is only linked to the Trim Stab of those axises. What you can do, and that would be the closest to the reality, is to link your strong motor to the fsuipc offsets of each trim axis. ELEV_TRIM_DN 65607ELEV_TRIM_UP 65615AILERON_TRIM_LEFT 66276AILERON_TRIM_RIGHT 65613RUDDER_TRIM_LEFT 66278RUDDER_TRIM_RIGHT 66279If made so, your servos will always set the controls to the corresponding trim setting. While flying on AP your controls will move slightly each time when the trim is working, and once you disconnect it your controls will be in the right position.The main advantage of that setting ( and that's my interest because I never fly on AP) is to get when you flying by hand, is to feel the force feedback.example: After take-off ( trim set in take position - mainly around center)your motor will always bring your controls back to trim set position. As soon as you trim for the initial climb setting, your control should stay in the position your were holding it.I do have a question to you. You are saying having a very strong SERVO motor. If so with kind, because beside industrial heavy geared motors I do not see any of the R.C. servos having the force of acting on controls. GreetingsRoger

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Thank you, that helps quite a bit and makes sense. I don't have that much understanding of how it works, I just know it's possible.I don't know how strong my motors are, but I assume they are pretty strong because in size they are pretty big. They are taken from a real-to-real player, a tape machine used in recording studios.How strong of a motor do you think I would need?My main concern is not only to get it working correctly, but to get the right feel as well. Without actually gotten to fly a 747, that would be very hard to duplicate, but I am going to try my best anyway.I need to learn alot more about this, but if my motors are usable, I would like to make use of them for my yokes.I don't know. What do you think? Possible?Best regards,

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Kevin,It is a matter of torque in expressed in NM. Ask Mike Powell of mikesflightdeck.com. He has the technical background for that kind of equations.Roger

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Hi Kevin,Roger is correct. The key parameter is torque. Apologies in advance for the long winded answer. The short answer is: "Yes, probably, but it can get involved."The long answer:The static analysis (i.e. controls held steady) is pretty straightforward. If you have a 3 foot column and you want 10 pounds of force, you need 30 foot-pounds of torque. (I'm going to stick to English units for the moment) If you have a motor capable of providing 32 inch-ounces of torque (a value representative of small AC induction motors at stall), you will need some sort of mechanical transmission to scale the torque. As 32 in-oz is 1/6 ft-lb, the transmission should have a 1:180 speed ratio if there are no losses. Because there will be losses, the ratio should be higher to compensate, but let's ignore them for simplicity.The transmission can be done with gears, belts and pulleys, radius wheels, whatever.The dynamic analysis is a bit more involved. When you move the column, the transmission will put a torque on the motor's rotor causing it to spin. Because of the transmission's speed ratio, the rotor will spin much faster than if you had simply applied torque directly to the rotor shaft. Effectively, the transmission has multiplied the rotational inertia of the rotor. The force needed to move the column, then, is the sum of the static and dynamic loading (inertia) presented by the motor AND the rotating elements in the transmission.So, unfortunately, the situation rapidly gets messy. Setting up the static forces on the yoke is easy, but establishing the dynamic feel of the controls becomes much more involved. I realize the question started out as an AP topic, but if you're going to connect something to the column, you don't want to screw up the control feel.A typical approach to get the dynamics under control is to measure the actual force (torque) delivered to the column and use active feedback to control the motor power so the force (torque) on the column fits the flight model.Another approach is to reduce the peak force required and use a larger motor. If only 1 pound of force is needed at the top of the column, and a motor capable of 128 in-oz is used, the transmission ratio drops to 4.5. The dynamic effects become much less, even though the larger motor has a larger rotor inertia.So, now, on to the motor. (HA! you thought you were done.)You almost certainly have the right kind of motor, though perhaps not the correct size. AC induction motors deliver torque that varies with speed. A certain type of induction motor is designed to have approximately constant torque at stall and low speeds. Called a torque motor, it is (or was) frequently used on high end reel-to-reel tape decks (Ampex, Crown, etc.). Additionally, torque motors don't overheat like normal induction motors when stalled for extended amounts of time.Building a system based on torque motors connected to the controls would be an involved project, but would actually provide the means for dynamic control loading. This would be (as my daughter says) an uber-cool project.If you simply want to provide a slow shift in the centering force presented to the controls, you might instead consider using a lead screw to move a traveling nut that in turn is spring connected to the control. The lead screw could be turned by an electric screwdriver or cheap electric drill.Mikewww.mikesflightdeckbooks.com

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Thank you much for your answer. I'll have to do some research to really get into this, especially if I need to make a transmission. ugh. My knowledge of this is very little, so I might have to find someone in my area for some expert help.Never the less, I was trying to figure out how strong my motors are. I'm reading the label and it gives me some numbers, but I dont know how to read them, or what it even means.The motors are made by TEAC who makes Tascam recorders. It's 60V, 50/60Hz, 22/23W and what I dont understand is 5/4yF. I dont have the symbol for the "y" on my keyboard, but it looks like a y. See, I have no idea what I'm talking about. Maybe someone else does?Does it tell me how strong the motor is?

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It could be that the y-like symbol is the Greek character mu. It's like a script "U" with a longer tail. It means micro-. When in front of an "F" it refers to microFarad, the size of a capacitor. Many AC motors require the use of a capacitor.Determining the torque of the motor can be done by tracking down the manufacturer's data. Sometime this is possible online, but becomes more difficult the older a motor is. Another approach is to connect the motor to power and measure the torque.

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Yes, that is exactly what I mean, and I knew there was a reason why I saved some of the capicators from the machine as well. Is this an involved process you think to hook this up?What does the capicator do?I wouldnt even know what wires went where. lol.It says 60V on the motor. How and where would I get the power to drive the thing?

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It can be an involved process in the absence of documentation. Some motors have multiple windings, not all of which are used at the same time. When you have a lot of wires, it gets increasingly confusing. Some tape transports switched diferent value resistors in series with the motor windings to vary the torque. Low torque was used for tape take up and tensioning during play and record, while higher torque was used for rewind and fast forward. Other transports perhaps worked by selecting different motor windings.The capacitor is used to provide a phase shift in the current of one of the motor's windings. Induction motors work by creating a rotating magnetic field that drags the rotor around. You need sine and cosine magnetic field components to produce a composite rotating field. The capacitor phase-shifts the single AC power phase to produce a second AC power phase. Hmmm, techno-mumble-jumble. Short answer: the cap makes the motor go 'round.The 60 volt rating is non standard. Are you sure that's what the label says? A more standard power rating for US equipment would be something like 110 to 120 volts at 60 Hz. Sometimes you will see a rating that says 60 volt-amps which is not the same thing as 60 volts.Mikewww.mikesflightdeckbooks.com

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I took some pics of my motor with my cheap webcam. Hopefully you'll be able to see, and read the label. 60V right?U think this motor is duable?http://www.absoluteplanes.com/images/news/motor1.jpghttp://www.absoluteplanes.com/images/news/motor2.jpghttp://www.absoluteplanes.com/images/news/motor3.jpgLemme know what you think.I have two of these, plus one smaller one. The smaller one runs on 100V.

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Sure looks like 60 volts, doesn't it. It also explains the 5/4 uF. Taken in conjunction with the 50/60 Hz it means use a 4 microFarad cap when used with 60 Hz power.The 22/23W means it's a fairly low power motor (23 watts when run on 60 Hz power) with limited torque. Mikewww.mikesflightdeck.com

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"The 22/23W means it's a fairly low power motor (23 watts when run on 60 Hz power) with limited torque."Does that mean it's not a good motor to use?Also, I need to figure out which capasitator to use, plus which component in my reel2reel is the transformer for 60V power supply.What is the preferred software to hook this up to?regards,

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Whether it's a good choice or not depends upon what you expect it to do. How fast, how much force, how it is coupled to the column and so on. It gets very involved.As for software, I expect a large portion would have to be written specifically for the application. FSUIPC could be used to pull data out of FS, but you still have to control an as yet undefined, undesigned motor control unit.

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Ok, that is really involved, and not anything I'll be able to do on my own. FSBUS has nothing I can use?

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Hi Mike,Do you think it could be possible to use the electronic part of a standard servos, to put the 22K pot on the gear of a high torque motor and drive it with any servo card ( Phidget - Fsbus - Iocard etc...) ????What would be the issues in that configuration??GreetingsRoger

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Hi Roger,Qualified yes. You would have to use some sort of power buffer between the servo electronics and the larger motor. The servo electronics is designed for a particular electrical power demand that a larger motor would quite likely exceed.There could well be dynamic issues. Imagine a powerful motor which spins too far and overshoots relative to where the servo control electronics is trying to position the output shaft. The motor then overcorrects and undershoots. The servo electronics is "tuned" to a particular set of parameters that include motor torque, inertia and power gain. Changing motors will upset this. Since all these paameters interact, it is hard to predict offhand just how well or poorly a motor substitution will work.Mikewww.mikesflightdeckbooks.com

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Kevin,I don't use FSBUS and haven't kept up with its cuurent capabilities, so can't really say.Mikewww.mikesflightdeck.com

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Hello Mike,Thanks a lot for the explanation. Your answer takes me to an other question:There must be someboby ( who knows probably you)out there able to design the electronic and the pcb of such a circuit. Greetings from France,Roger

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>Hello Mike,>>Thanks a lot for the explanation. Your answer takes me to an>other question:>>There must be someboby ( who knows probably you)out there able>to design the electronic and the pcb of such a circuit. How about that:http://www.bobblick.com/techref/projects/sv2hb/sv2hb.htmlIt takes a Servo PWM signal (as FSBus, Opencockpits, PHCC, ... can generate them) and uses it to control a motor (two actually).All you need to add are the feedback pots and some code for the microcontroller to use it.Still not a beginner circuit as motors generally draw lots of current and thus there's the potential of lots of smoke :)Manuel

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Manuel,I am absolutely unable to write ever any codes for a chip like the PIC or any other kind of microchips. I have a very superficial understanding of what I am doing. I have an creative approach on such issues, not the knowledged technician one.But as far as I understand, the circuit of basic RC servos motors seems not to be that complicated. There must be somebody able to design such a servo circuit for high torque motors.I think that the servo approach for a feedback on the controls is more appropriate since they move in an small angle:about 60

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>Manuel,>>I am absolutely unable to write ever any codes for a chip like>the PIC or any other kind of microchips. >I have a very superficial understanding of what I am doing. I>have an creative approach on such issues, not the knowledged>technician one.>>But as far as I understand, the circuit of basic RC servos>motors seems not to be that complicated. >There must be somebody able to design such a servo circuit for>high torque motors.Hi torque motor means hi amperage drivers... and thats where things get a little more complicated and more expensive.It probably would be better to buy a industrial type servo complete with controller circuit. Ebay might be a source for this.I don't know if those servos can be controlled with RC-type PWM servo signals.>I think that the servo approach for a feedback on the controls>is more appropriate since they move in an small angle:>about 60

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Roger,It looks promising, but Oatley has posted very little documentation. It appears they have added power transistors to buffer the output from the standard RC servo control chip. Without Oatley specs and information about the motor it is expected to drive, it's hard to say. Mikewww.mikesflightdeckbooks.com

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Roger,>Did you take a look here ???>http://www.oatleyelectronics.com/kits/k165b.htmlYes, I did.I just tried the chip name they mention on google, and it returned a data sheet:http://www.oatleyelectronics.com/pdf/m51660e.pdffrom the same site.500mA is what this chip can drive. Hardly enough. And this would still be a DC motor, but you mentioned that you'd like to use AC motors.When I looked at the site earlier, I saw the circuit picture. If you could drive high loads with it, then there'd be a big transistor, probably with heatsink. Not seeing this, and as the text seemed to indicate that the target audience are RC models and such, I concluded it would not suffice.Manuel

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