Recommendation for a servo motor

[Devon Custard]

I ordered a couple of HS-55 servos to try and build some of the engine gauges in the A10, however seems the motor is restricted to 180 degrees of movement. From looking at the gauge faces im going to need about 300.

 

Anyone done this already and have a servo recommendation? Only other alternative i can think of is to build a gear train, however i really dont want to have to do that 12 times at that scale of precision.

[Boltz]

I found exactly the same problem and I know that hegykc is planning on using gears but you would have to make sure they had no slack in them to keep precision.

 

Another alternative is to use stepper motors like overpro did (http://forums.eagle.ru/showthread.php?t=115997) however this would require a circuit and programming to calibrate the motor and get it back to the 0 degree position.

 

Servos can also be modified to remove the block that prevents it turning past 180 degrees but you would also have to remove the potentiometer and find some other way to calibrate the sensor (Overpro used a light sensor, if I remember correctly, to do this.) This creates a motor and gearbox that can be controlled by simple servo commands.

 

A tutorial for modifying a servo can be found at simkits (http://www.simkits.com/brochures.php) and scroll down to the "Manual "How to modify a HS-322 Servo"" I don't know whether this only covers that specific type of servo but if you opened up one of yours you could probably work something out.

 

Also as another note, will you be including the 10's needle on the ITT and 1's needle on the core speed indicators? I use them a lot as they make it a lot easier than guesswork from the main gauge when + or -1 is going to make a difference. They would be geared 10:1 off of the main shaft.

 

I think your project is going to get me building the EMI as well

[Mike Powell]

If you decide to go with a standard servo and gears, ServoCity is a source of gears which fit on the servo spline. http://www.servocity.com/html/servo_mount_gears.html

 

If you decide to go the stepping motor direction, you can still find a sample chapter from the out-of-print book Building Simulated Aircraft Instrumentation online at: http://www.mikesflightdeck.com/downloads/BSAI%20Sample%20Chapter.pdf This will give you an idea of one approach.

 

For small, single pointer gauges consider using stepping motors designed for automotive instrument gauges. They're cheaply available through multiple vendors on Ebay, for example search ebay for item 310445275703 or use the search terms "stepper motor gauge". I prototyped a gauge using one a few years back, see the 15 Sept 2011 entry on this page: http://www.mikesflightdeck.com/oldnews/oldnews_2011.html