Asi

This thread will show my construction of an airspeed indicator using the techniques in Mike Powell's book.
So far I have the faceplate and motor deck constructed from 0.064" aluminum.
The motor was salvaged from an old HP Scanjet flatbed scanner, it is a nice little 1.8° stepper.

I hope the pictures work, I am using Facebook to save my poor home DSL connection.

http://photos-f.ak.fbcdn.net/photos-...38765_7196.jpg
Laying out the holes for the motor deck

http://photos-g.ak.fbcdn.net/photos-...38766_7481.jpg
Faceplate and motor deck

http://photos-h.ak.fbcdn.net/photos-...38767_7816.jpg
Motor deck from rear

My wife was totally unimpressed, but maybe somebody here will appreciate what I am trying to do. :)

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Originally Posted by wriley

My wife was totally unimpressed,

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Yup! Been there. ;)

Wow, looks great Wriley, tell us a bit about the servo motor and how you plan on interfacing it.

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Originally Posted by ak49er

Wow, looks great Wriley, tell us a bit about the servo motor and how you plan on interfacing it.

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Thanks for the kind words.

I haven't decided yet on how I am going to interface my instruments. The OpenCockpits stuff looks great but I may roll my own since I am familiar with Atmel AVR microcontrollers and enjoy that hobby as well. The downside would be having to write my own software. SIOC looks very nice and all the hard work is already done. For now I am enjoying dusting off my fabrication skills.

I have started prototyping a USB-interfaced GA nav/com unit so have a head start on rolling my own, but that is for another thread someday. :D

Final test assembly before painting. The only mechanical piece left is the connector that joins the stepper motor shaft to the pointer shaft.

A big thank you to Jackpilot for sending me the faceplate graphic.

http://photos-g.ak.fbcdn.net/photos-...42198_5951.jpg

http://photos-h.ak.fbcdn.net/photos-...42199_6294.jpg

http://photos-a.ak.fbcdn.net/photos-...42200_6608.jpg

http://photos-b.ak.fbcdn.net/photos-...42201_6925.jpg

http://photos-c.ak.fbcdn.net/photos-...42202_7294.jpg

That is a graet looking ASI, can i just ask if the acrylic as used in the cutout is for back lighting, is there a reason you have acrylic (clear plastic)?

Alex


Ps.How the heck do you make gauges that requires 2 pointers? does that completely change the design of the DIY gauge?

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Originally Posted by alexpilot2008

Ps.How the heck do you make gauges that requires 2 pointers? does that completely change the design of the DIY gauge?

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You can use brass hobby tubing to make concentric shafts. Jan Verley has posted pictures of his DC-3 gauges here: http://home.versateladsl.be/verlejan/instr1E.html

Also, take an extended look at Scott Hendry's superlative gauges: http://home.exetel.com.au/flightsim/Engine_Gauges.htm

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Originally Posted by alexpilot2008

That is a graet looking ASI, can i just ask if the acrylic as used in the cutout is for back lighting, is there a reason you have acrylic (clear plastic)?

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Thanks! Right now all I can see is the crooked faceplate deck and the misaligned holes in the light diffuser deck and the... but I'll get over it and do better on the next instrument. :D

And yes, the thick acrylic is there for back lighting. You can't see it in these photos but there are four holes drilled into the back of it for LEDs.

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Originally Posted by alexpilot2008

Ps.How the heck do you make gauges that requires 2 pointers? does that completely change the design of the DIY gauge?

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The basic construction is the same but you add a concentric shaft and gearing. It's all documented in Mike Powell's excellent book. ;)

http://photos-f.ak.fbcdn.net/photos-...52733_2141.jpg

http://photos-g.ak.fbcdn.net/photos-...52734_2427.jpg

Nice work. I love to see people who can build their own stuff.


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Here are some renderings of the circuit deck I designed.

The schematic and PCB were done with the free version of Eagle CAD and rendered using POVRay and Eagle3D.

The circuit is built on my breadboard and spinning a stepper with some quick diagnostic firmware so I am about ready to etch the PCB. Once the PCB is populated I will be tackling the full firmware.

The bottom view.
http://photos-h.ak.fbcdn.net/photos-...55871_2449.jpg

The top view. Note that not all parts I have used are modeled in 3D so they are not populated.
For example, at bottom center should be a USB connector and the large pads on the lower left are for a floppy style power connector.
http://photos-a.ak.fbcdn.net/photos-...55872_2764.jpg

I took my first flight with the ASI this weekend! I don't have a video of it in action yet but will soon. It is so cool to watch the ASI I built react to FSX. :D

The values on the gauge are not linear so I had to do some googling and dust off long unused math skills to do linear interpolation. I use eight known positions on the gauge and interpolate the other values.

The firmware that controls the gauge is pretty well complete but the software that gives values to the firmware is still rough. I used a simple C# program that pulls the IAS from FSX via FSUIPC, does some math to map to the required stepper position, then sends that value to the gauge firmware. This program needs a lot of polishing.

I will eventually be posting the circuit and software designs on my blog for anyone that is interested.

A short video of my test program exercising the ASI.

http://www.youtube.com/watch?v=Hgv5Uy-xzuE

Hi Wriley,

Can i just ask how you learnt how to make all this? because i really want to make my own gages but i just havent a clue where to start? Where should we all start if we'd like to make a simple gauge like this?

Cheers buddy!

Alex

Hey Alex. Get Mike Powell's First book. Thats a great start, and its worth every penny.

Trev

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Originally Posted by alexpilot2008

Hi Wriley,

Can i just ask how you learnt how to make all this? because i really want to make my own gages but i just havent a clue where to start? Where should we all start if we'd like to make a simple gauge like this?

Cheers buddy!

Alex

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Hi Alex,
That is an excellent question. I guess I learned how to do this by tinkering for about twenty-five years. :D

I think anyone with a little bit of mechanical ability can construct the gauge itself. I followed the design ideas in Mike Powell's book and made this gauge with very simple tools. At a minimum I would recommend having a drill press, a bench vise, hand files, calipers, and a hacksaw, along with the usual assortment of pliers, screwdrivers, etc. With these and some patience you should be able to build a simple gauge.

The next step would be constructing some sort of electronics that talks to a computer. Mike provides everything you need for one way to build this in his book. I prefer Atmel AVR (Mike uses Microchip PIC) microcontrollers and have some experience using them so I designed my own gauge circuit. When the design is complete I plan to make my schematics, firmware and PC software available as open source. The PC software will be more of a guide rather than a plug and play solution since it will most likely be tailored to my particular cockpit. If you have no electronics background you could use any number of off-the-shelf stepper or servo control boards such as those offered by OpenCockpits or Phidgets.

After you have the mechanical gauge and some electronics to make it move you need some software on your computer that makes the connection between your flight simulator program and the gauge. I have just enough programming skills to be dangerous so I am writing my own in Visual C#. You can download an express version of Visual C# for free from Microsoft here. I am getting the data needed to drive my gauges from FSUIPC so I started with the C# example provided with the FSUIPC SDK. If you don't want to tackle programming then you would need to use something off-the-shelf, such as SIOC for OpenCockpit's hardware.

As you can see there is a lot of opportunity for DIY but you can also mix and match with commercial pieces. If you don't know where to start I would recommend getting Mike's book, visiting your local hardware store for some materials and start building something. Start simple like I did with an easy gauge like an ASI or gyrocompass and go from there. This is one of the most helpful, friendly forums I have seen so you can count on plenty of help!

Hi William

Glad I could (slightly) contribute...Looks really great!
Cheers
Jack

Hey, cheers for the advice wriley!

Mikes book seems a good bet, there is a sample chapter of how to make a gyro compass using the stepper motor on his website, so may start making the compass! Shouldnt be nothing too hard i hope!

I'll update you shortly!

All the best!

Alex

I had a run of PCBs made for a USB stepper driver that can handle two stepper motors, 2 encoders, 1 switch and 2 optical interrupters (or switches). There are still a few parts needed that I don't have in stock. I can hardly wait to complete this ASI and fly with it. :D

http://www.mycockpit.org/forums/atta...1&d=1256259426
http://www.mycockpit.org/forums/atta...1&d=1256259426
http://www.mycockpit.org/forums/atta...1&d=1256259426

Looking good! You might want to consider buying a small lathe, like a TAIG or Sherline to help with the tricky concentric parts.

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Originally Posted by WJH308

You might want to consider buying a small lathe, like a TAIG or Sherline to help with the tricky concentric parts.

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I have considered a lathe many times, then my wife gives me that look. :shock:

Back in college I did an engineering internship and had access to a very nice, fully stocked machine shop and a master machinist. Boy do I miss those days!

One of the many things I like about Mike Powell's first book is how he has figured out how to make the instruments without the need for a lathe or mill. I am getting passable results with a small drill press, a band saw and basic hand tools.

One more picture update before bed time. I fired up the soldering iron and got most of the board populated, then stuck it on the ASI.

http://www.mycockpit.org/forums/atta...1&d=1256275863

Fantastic work wriley! :D

I almost went down the build-your-own-route, but I found the USB link the tricky part. It would be great to see how you've written your software USB interface. I've always used FTDI chips and gone with rs232 at the software end.

Great mechanical skills too. If you need any more faceplates let me know. I have some left over from my Simkits gauges before I sold them...

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Originally Posted by CrashEd

It would be great to see how you've written your software USB interface.

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I would be embarrassed to share my beta code right now. :) Once it is fit for public consumption I will be releasing the hardware and software design for my USB boards as open source.

I fixed some minor issues with the PCB and declare the hardware build for the ASI complete. Now I need to finish my MIP so I can put this sucker on it. :roll: The fun never ends!

Note: The cool white faceplate is courtesy of forum member Tripacer, thanks!

http://winchester.homelinux.net/pics/ASI_pcb04.jpg
http://winchester.homelinux.net/pics/ASI_pcb03.jpg
http://winchester.homelinux.net/pics/ASI_pcb02.jpg

Beautiful work mate, well done.

Hello Wriley

I Follow your project and I am impressed of what you are able to do.

I do not have your skills, so my first attempt is a MIP with an LCD screen.


You can buy almost everything you need for Heavy cockpit building ...

but a "simple" thing as an 80 mm bezel seems to be impossible to buy.

I really wonder why .............


Now to my question !

Did you make your bezel with an CNC machine ?


Best Regards

Bjarne Horsboel
Copenhagen, Denmark

That is some fantastic work. this has definitely inspired me to purchase Mikes book and attempt a build myself.

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Originally Posted by bjarnehorsbøl

Hello Wriley
Did you make your bezel with an CNC machine ?

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Hi Bjarne,
The white plastic bezel was made for me by member Tripacer. Everything else was made by me with basic hand tools.

Happy simming!

While on vacation I managed to squeeze in a few hours of coding to get my ASI working with FSX. Even with only one gauge it was very rewarding to see my hard work pay off with a working instrument. The software is alpha quality and needs a lot of debugging but it works! At some point in the future I will be releasing all this software and firmware as open source for the curious.

I didn't get a picture of the ASI sitting on my desk while I fly, but here are some screenshots.

http://winchester.homelinux.net/imag...irstflight.jpg
The interface software (usbSimCentral) and FSX

http://winchester.homelinux.net/images/Calibrator.jpg
Calibration tool

Time to build another instrument!

G'Day all.
I know this thread is a bit (5yrs) old, but wondering if anyone had a copy of Mike Powell's book they don't need anymore? I have tried everywhere without luck. Tried convincing Mike to turn it into an Ebook without any luck.
By the way, great work William. Is the circuit the one that is provided in Mike's book?

Thanks in advance,
Rob
Australia.

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Originally Posted by rjfon1

G'Day all.
I know this thread is a bit (5yrs) old, but wondering if anyone had a copy of Mike Powell's book they don't need anymore? I have tried everywhere without luck. Tried convincing Mike to turn it into an Ebook without any luck.
By the way, great work William. Is the circuit the one that is provided in Mike's book?

Thanks in advance,
Rob
Australia.

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Hi Rob,
I used my own design to drive the steppers. You can find the half-finished work here: https://github.com/wriley/usbSimStepper, use at your own risk. I've been out of the loop on sim stuff for quite a few years due to other interests and demands.