More Engine Monitor Updates

This will be kind of a quick post, but the gist of it is, I've been busy. In between getting a new version of my other app out, and explaining the technology behind these gauges on my other blog, I haven't been watching a lot of TV or hanging out in bars.

The new gauges have options that work, and the interface and abstract implementation make these very flexible. Looking at all the gauges, they mostly have the same call, the size differences are sort of hard coded.

In the picture above, you will see round and bar gauges, mostly the same as before. The new changes are the round gauges can go in either direction, be 270 degree, or 180 degree (any sweep angle should work) There is one CircleGauge class that actually draws them all! The CircleGauge class is extended by things like the Ammeter class, or the Volts Meter class.

The gauges have options for clockwise/counter-clockwise, ticks, and various color options (I haven't been setting the color options, these are the  default values. The gauges can have a rotated start angle, and display the title and value in the center of the gauge.

The gauges all get their values from an EngineValues class, that can be set at any time. The next steps will be to put in the bluetooth reading code that will allow me to connect the Arduino to the engine and start measuring values.

What-cha think? Am I heading in the right direction?

Getting Back at It

I've finished my other Android app. It is non- aviation related, and it doesn't use an Arduino, but it proves my skill as an Android developer (or not). It may be in the Playstore real soon now. The weather is warming, and I can get at the plane in the hangar, so I am going at least make an effort to move forward with the engine monitor project.

I've been playing with the Android PFD that I really like. The  A-EFIS is really nice, and I can see this as the primary display I use going forward. Long term, before I would fly any tablet in IFR conditions, I would like a AHRS system bolted to the aircraft, and connected to the tablet. This app is good enough for daily use otherwise using only the tablet gyros. I tested this while flying on a commercial flight (I wouldn't want to test and document while flying solo in GA). 

It is time to replace the engine instruments with an Android app. I have the skills, and proved that I can get the data, I just need to put it all together. So I will document my design with this post, and move on to actually finishing it, showing my test results. I look forward to your feedback, and want to know your thoughts.

I am trying to use best practices, so I will try to use modern technology, and communications. It will still use the Arduino, since that platform is reliable and well documented.

Using the 3 layer design Model, View Controller (MVC) pattern, I will use the Arduino output as the Model, the Android display as the View and the logic to monitor and log the data as the controller. There may be redundant logging on both the Arduino and the Android. The Arduino will be attached to the aircraft, and have the aircraft data. The Android will be removable, and allow interpretation and modeling at remote locations.

The Arduino will read all the raw values from the sensors, and convert those values to actual real numbers. The actual message will contain units, so the numbers have a context.

The output from the Arduino will be in JSON format, allowing different platforms to use the information.  Someday someone may want to replace the Android display with another platform, and that will be possible using this design. The message will be sent from the Arduino about once a second, but can come more often.  A sample message will be similar to:

{"engineParams":
     ["CHTS":[
        "Cyl1": "340F", "Cyl2": "341F", "Cyl3":"348F", "Cyl4":"333F" ],
      "EGTS":[
        "Cyl1":"1530F", "Cyl2":"1520F", "Cyl3":"1550F", "Cyl4":"1545F" ],
      "RPM": 2330,
      "OilPress": "50lb",
      "OilTemp": "220F",
      "FuelPress":"25lb",
      "Volts" : 14.2,
      "Amps" : +12.3,
      "ManifoldPress", "32.29InHg",
      "Timestamp", "2142325533.5sec"]}


The Android will use this information to display graphically the current engine situation. The Android will be able to interpret these values and display the data in other units, set monitoring points with alarms, and other alerting mechanisms. Logging will try to be as similar to the Insight engine monitoring data formats (CSV), allowing existing analysis tools to utilize this data, and make common sense results.

Some of the alerts will include:

• Low oil pressure
• High CHT
• High oil temprature
• Low voltage
• Low charge (amps)

As well as others can be programmed in.  Blinking displays and audible alerts are possible, and a combination will be used. The audio output from the Android device can be routed to most audio panels. The Android device may allow playing music, podcasts  and other entertainment functions along with the alerting functions.

Using the JSON input format can allow debugging and testing on a desktop computer. Creating or using recorded data can allow playback to the Android device. The Android emulator included with the ADK is very good, and allows devices of all types to be used, to insure the display will work. I can start working on the Android code without having a functioning Arduino device working.

I welcome your input