Started building gauges

[mondo50m]

I have recently started to build a gauge for the Bell 206 that I would like to be able to complete sometime in the future. The gauge pictured below is just the first build for the oil pressure gauge which has 2 needles. More work to be done to perfect the gear sizing, but it is going pretty good. Need to find out how to use a position sensor that will be needed for some of the gauges. As I progress with this gauge and it is working to my statisfaction, I will post pictures of all of the parts that I have made for it. If anyone can give me insight to what I need to do or how to set up, or what is needed for the position sensing part, please let me know.

Milt

[AK Mongo]

Mondo,

I just got Mike Powell's book about instrument building, and it looks like a great reference. Maybe a little over my head until I get started, but most of this hobby is! Using servos, you should just need a servo control card.

Was there another problem you are trying to solve?

I love your bezel. Did you cut those on your cnc?

[mondo50m]

THE BEZELS;

I used a 1/2" thick piece of HDPE to create a mold. This was done by first 'pocketing the square size. Then I used a 1/8" bull nose cutter to a depth of 11mm. This gave me the room to mount the bezel from the back of the panel. In a Bell 206, there is no square section on the front of the panel, only the round bezel itself. Then ii is just a matter of getting some casting acrylic at the craft shop and keep molding until you get enough of them.

WHAT I NEED TO KNOW;

Some of the gauges require one to have servos be able to turn past 360 degrees and keep going. I have that part done. Now, there is a way to use a some kind of sensor to have the gauge return to zero. The servo itself will not do this as it has been modified to run past its default ability and it needs to be told where 'zero' is in order to return. That is what I could use some help with. I could probably figure it out, but somone has to know how to do this here.

I have already proved out that the gears are ok and the servos work. I am using the FSBUS servo card for this. So that part is good.

Milt

[Jordan Farmer]

Well usually, a 360 degree motion instrument uses 'stepper motors'. but anythi ng will do i guess, and a simple way that i have read once before is to use a simple 'optical interrupter'. This is a simple device which blocks an optical gate at zero position. Now dont ask me how to program it, as i dont have a clue :p

jordan

[mondo50m]

Thanks, every bit helps.

Milt

[mondo50m]

AK Mongo, I would love to be able to get Mikes book...........but thngs are not good

Milt

[wannabeaflyer]

Hi Guys just a thought have seen other builders using servos for instruments and they appear to use gears of different ratios to overcome the 360 degrees issue
and over at opencockpits a whisky compass is made and driven via their usb Servo Card and utilises an optical interupter for Referencing - not stating any thing new here just thought i'd add that im also interested in DIY instruments ideally driven by a POLOU servo card or my Opencockpits Card got all the bits ( am a natural Hoarder LOL :-) Just not gotten round to putting something together this seem like a good place to bounce combined ideas off each other :-) version have had both mikes books now for some time but until i got my CNC router going again sorta mothballed this part of my cockpit build . mind you does anyone out there know a good source for printed Faceplates ( Dials ) .. ideally would like to have these guages fed data from FSX - FS2004 through a PIC microchip Serial data / USB would be better and then to the instrument via either contrller Interface , Dont know if anyone out there has gone down this route so putting out feelers as it were ....

[AK Mongo]

Milt,

Just found a sample chapter of the book that deals with the optical interrupter...

http://www.mikesflightdeck.com/Downloads/BSAI%20Sample%20Chapter.pdf

Hope that helps.

Reid

[RobiD]

Hi Mondo,

I used Mike's book. Brilliant!!

CNC'd all the parts including the pointers. I have used everything from AirCore, servo and now stepper.

I used the optical interupers for the steppers in order to give the zero point. I too am using FSBus. There is a problem at present with the stepper cards and the version 2 dll. I have comunicated with Dirk (the designer and programmer of FSBus) and he says that he is working on a solution. So hopefully we won't have to wait toooooo long.

I'll attach a couple of photos on the optical interupter set up on my Altitude indicator. It is driven by 1 stepper but has 3 optical interupters to ensure all 3 needles are zero'd.

http://www.safeweightloss4kids.com/dontlookhere/Picture 007.jpg

http://www.safeweightloss4kids.com/dontlookhere/Picture%20006.jpg

[Marsh]

Servos can be hacked or bought to provide continous rotation (360+ degrees). The trade off is then you lose the positional feedback. You can tell the servo move x steps forward or back, but the servo doesn't know where it is. Basically behaves like a stepper motor.
Can't always get the rotation you need out of a servo anyway. For example a vertical speed indicator. A VSI doesn't need to spin a full circle, but you need to at least get that needle to swing 350 degrees. To do that out of a servo that only swings 180, you need some sort of gearing.

[Tripacer]

Milt,
Very good start. I have been building instruments for about a year now and have five completed. I second MikesFlightDeck books and his web sight. I use servos for gages that odn;t have to turn through a large range. In a standard airplane fuel, oil pressure, oil temp, and other guages fall into that category. For guages that require a full 360 degree rotation like an altimeter, directional gyro compass and so on use a small stepper. These systems do require some type of zero position sensor at start up. I am driving my guages with PIC microcontroller circuits. However, other options exist like Opencockpits cards and even the Arduino controller board. All of these require programjming ot both the pc level and at the instrument level to operate correctly.
You can find several pictures of my guages in the gallery section. I also made a mold for a 3 1/8 and 2 1/2 in guages so that I can cast bezels that all match.
Keep us posted about how you are solving these problems. Now you know why so many folks are building Boeing 737s with all glass cockpits.

Tripacer