Archive for the ‘Flight Sim’ Category

A Nav/Com radio for the cockpit

Saturday, February 20th, 2010

Unlike the wide body boys there do not seem to be any affordable options for us general aviation simmers when it comes to the radio stack. Sure there are some fantastic products out there, the SimKits line for instance, but they are priced higher than the Chief of Finance will allow. There are also some cheaper alternatives but in my opinion they sacrifice too much in realism. So, like my instruments, I decided to build my own.

I am starting with a nav/com unit based on the Bendix King KX165 like the image above. The biggest obstacle was finding a suitable display that wouldn’t break the bank. After a lot of searching I came across a 4 digit 7-segment display at Futurlec that was priced reasonably and the correct size. Using the dimensions provided at Futurlec I mocked up a display. While the spacing is tighter than the real thing I think it is close enough for my purposes.

With the display picked out and on order I worked on a face plate design. I am thinking about using 1/8″ plexi covered with a printed label. Here is my CAD design.

For the most flexibility I decided to build a microcontroller based circuit to communicate with the host PC and control the display. Like my instruments this nav/com unit will connect via USB and be controlled by my usbSimCentral program. I proved out my display driving circuit on a breadboard because I was concerned about being able to refresh 20 digits quickly enough. It works fine with no flicker.

Here is the schematic for the display board. This includes the 7-segment displays and shift registers as well as the encoders and buttons.

The PCB design is a little more complicated than needed because I am etching a single sided version with jumper wires for the prototype. If there is enough interest I plan to sell a kit version and will have boards professionally made for that.

The next step is to etch the two boards. I also need to order a few parts as I do not have the surface mount shift registers or encoders. This is a work in progress, stay tuned for updates.

Flying with one instrument

Sunday, December 27th, 2009

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.

The interface software (usbSimCentral) and FSX

Calibration tool

I think I will build the attitude indicator next.

ASI build complete

Tuesday, December 15th, 2009

I completed the build of my ASI (air speed indicator) for my flight simulator project. There were some minor issues with the PCB but nothing a few jumper wires couldn’t fix. The most frustrating “bug” was with the USB connector. For some reason the connectors I ordered have an unconnected ground pin. Ground is instead connected to the case or shield of the connector. Once I added a jumper from the connector case to the ground pin everything worked great.

ASI_pcb04 ASI_pcb03 ASI_pcb02

You may have noticed an empty IC socket and unused connectors on the PCB. That is because I designed the board to support two stepper motors, two limit switches, two encoders and a switch but the ASI only uses one stepper and one limit switch.

Time to build instrument number 2!

usbSimStepper PCBs have arrived

Tuesday, October 27th, 2009

I designed a dual stepper motor controller that interfaces to a computer via USB for use in my flight simulator. These boards will drive various instruments, such as my airspeed indicator. This is the first time I have used Seeed Studio for PCBs and I am very please so far with the end result. The total cost was right at $50 for 11 of these boards which measure about 3 inches square.

usbSimStepper01 usbSimStepper02 usbSimStepper03


Here is one of the boards mostly populated with parts and installed on my home made airspeed indicator.



Update: There were a couple of minor errors on the board layout. Here is an updated schematic.