Avionics Bending - PCB Design: VHF COMM Radio

The next step in creating the I/O interface for the VHF COMM radio heads is to create the PCB. I try to make the PCBs as much multi-function as possible so that they will fit a number of different devices that I use for the Lockheed L-1011 project.

When you click on the image above, you will see that I decided on a two layer (TOP/BOTTOM) design. The BOTTOM layer has a few outward facing components such as the MULTI PURPOSE POWER CONNECTOR (MPPC) and the USB connector. There is also a jumper that enables the board (can be coupled with a fake circuit breaker on the overhead panel) and a LED indicating power status of the device. The bottom of the PCB features a large ground plane to ease with the noise from the many other radio heads.

I used CADSoft's EAGLE to design the schematic and the board and I will use PCB-POOL to have the boards made.

The board has a size of 4.5" x 2.45" and will fit behind most of my radio heads .... but you will see the mounting process in a later posting.

Avionics Bending - Schematic: VHF COMM Radio

Here is the first of 7 postings that will show how I implemented the I/O board for the VHF COMM head as part of my Lockheed L-1011 project. First, let me describe the schematic to you:

A few weeks ago I posted a design specification document that asked for a micro-controller that has USB support. This was a relatively easy decision because I right away picked a micro-controller made by ATMEL. To be exact, i picked the AT90USB1286. So what better way to avoid SMD's than using the teensy++ as a mezzanine board for my project. However, the chip is only available as a surface mount (SMD) and my shaky hands a are not steady enough to solder a board with SMDs together myself. However, for the first go-around of this hardware solution I wanted to avoid the cost of having the board assembled. However, I found the AT90USB mounted as part of the teensy++ as sold by PJRC.

Besides the mezzanine board, I also have connectors for the Digit Drum and Light Plate illumination that is controlled externally. The Mark-I version of the board does not have a WatchDog implemented ... I will add that for Mark-II.

This multi-function board will provide the following:

• On-Board Power Conditioning to 5V
• 32bit or 40bit Input only
  
• 8bit ADC or 8bit High Current Output
• Analog Reference Input (AREF)
  
• Two basic analog inputs (AIN1/AIN2)
  
• Two Instrument Light Connectors (DRUM1/DRUM2)
  
• One Light Plate Connector (LB)
  

The idea is that the board will be usable for all drum-style radio heads, the transponder and the weather radar head .... amongst others.

You can check out the schematic as an image above, or you can click on the link to see the schematic as a PDF file: Radio Head Schematic

Avionics Bending: VHF COMM Radio

Over the past few weeks I have designed a multi-purpose I/O interface for the Lockheed L-1011 project that will allow me to attach a number of radio heads to X-Plane. The first radio head to attach to the flight simulator will be a VHF COMM radio. A few postings ago, I showed you the
breadboard prototype of the proposed electronics.

Over the next few days, I will take you through the following:

Posting 1: The schematic for the I/O interface
Posting 2: The PCB design
Posting 3: The finished PCB
Posting 4: The assembly and attachment of the PCB to the VHF COMM radio head
Posting 5: The radio head firmware
Posting 6: The computer receiver module
Posting 7: The X-Plane plug-in

So stay tuned, over the next few days we are going to go deep into hardware and software interface design.

Field Trip: Tucson Arizona - UNITED Boeing 727

Have I already stated that I absolutely love tri-jets. Well, of course I do, that is why I am building a Lockheed L-1011 simulator. My second favorite tri-jet is the Boeing 727. Just like the L-1011, the B727 is no longer in regular service in North America. The pictures in this posting are from the the UNITED Boeing 747 tail number N7004U .... according to the Pima Air Museum folks .. the first B727.




It is certainly interesting to see that the "S" duct design on the B727 is much more "free" standing than on the L-1011. The "S" duct for the #2 engine on the L-1011 is a lot more integrated into the fuselage as compared to the B727.

Field Trip: Tucson Arizona - Titan II Rocket Motor

A few more postings from the trip and we will back to the Lockheed L-1011 stuff ... i promise. Today I want to share a few pictures from the first stage Titan II rocket motor with you. To get the full explanation of the Titan II missile ... click the link.



The butterfly valve in the picture below was used as a safety mechanism. The valve had a key combination that could only be unlocked from the control room. I guess this was a safe enough way to prevent accidental launch of the Titan II missile.

Field Trip: Tucson Arizona - Titan II Missile Museum

Another stop on my recent trip to Arizona was at the Titan Missile Museum just outside of Tucson, AZ. The museum is an absolute must visit if you are into aerospace design. I you can look beyond the deadly purpose of the Titan II Missile site, you will see nothing be excellent and awesome engineering.



The building itself is truly amazing, not only does it reach 10 levels into the ground, everything inside is suspended by large springs and coils. I would have loved to spend an entire day just photographing little engineering details.

The missile below, of course, is a dummy ... well, it is the real thing, but it was never in a silo prior to it being moved to the museum. But it still s a great example of Titan II missile design.


One of the coolest things is that they have a first and upper stage rocket motor on display. The engineering that went into the Titan II missile rocket motors alone would be worth spending an entire day at the museum.


These are not space suits ... the are suits used during handling of the rocket fuel.


Click on the image below ... you will see it in much better resolution. This is a panorama picture I took of the Titan II launch control room. Awesome technology ... this is a dream come true for someone like me who has a passion for analog computers and analog electrical design.




The picture below is the cable way between the control center and the missile silo. The pistons on the right and left are suspending the cable way. Think about the amount of clever engineering that went into designing this underground structure. The tour guide explained that every surface in the complex can move 18 inches lateral .... that's amazing!



The door in the image below is a 6000 lb blast door. The engineering that went into the hinges for the door is so exact that the door can be moved with little effort with just one hand.



Here is a view of the Titan II missile in the silo on the the same level as the cable way.

Field Trip: Tucson Arizona - Lockheed Constellation

So, I took a trip to Tucson, Arizona. It was mostly for work, but I managed to work a few hours in and visit a few of the awesome aviation sites in Tucson. Please forgive me, but the next few days I will annoy you with pictures from the Tucson trip. I just think they are worth sharing! Once I get the Tucson trip out of my system, we will head right back to the Lockheed L-1011 project.

This first posting I will dedicate to one of my all time Lockheed favorites -- The Lockheed C-121 Constellation



The first time I stood in-front of a Lockheed Constellation I was truly amazed by just how well that aircraft was engineered. Just look at the picture above and look at the immensely elegant design of the fuselage. In essence, the C-121 fuselage is an airfoil ... the design is nothing but amazing.



The last image is a panorama I took ... click on it and you will see it in much higher resolution. I think, a Constellation would fit perfectly into my backyard!