Avionics Flight Duration Alarm

I currently have a piece of avionics equipment that outputs a serial data stream. The stream contains a data field that is the total flight time--i.e., flight duration. I was hoping to find/pay someone to build a small external device that reads the serial data stream and triggers an alarm after a certain, user defined, flight duration is reached.

As a computer scientist, it is a bit beyond my skills to build. Ideally it should be a small lightweight box that is capable of reading the serial data stream and when a user selected duration (e.g., 1 hour) is reached an external LED and/or buzzer is triggered. The device should be capable of running off 12-14v DC current.

I can provide details of the serial data output stream coming from the avionics device. Here is an overview:

The RS-232 interface outputs pressure derived measurement, flight status as well as the GPS position. The ouput communication protocol is in "NMEA / pseudo NMEA”, with device specifier “PFA”.

The checksum is the 8-bit XOR of all characters in the sentence including the “,” delimiters, between but not including the “$” and “*” characters. All output messages are terminated with <CR><LF>

The Flight Status Data Packet is in the following format:

$PFA,FLT,f,s,dddddd,tttt,u,llll,v,aaaaaa*hh

where aaaaaa is the duration airborne in format HHMMSS, empty before takeoff

Thanks in advance for any help.

I might be able to help. I've done some work on microcontrollers that read in GPS strings. How would you want to set the flight duration limit?

Where abouts in the world are you?

That was quick!

I am located in London, England.

To your question on how to set the flight duration...I am not sure...I was looking for ideas. My overriding objective is try to keep it small. Maybe a small LCD (or numerical LED) display with small micro buttons for up and down...you could set the timer in 1 minute increments. For example, if 30 was displayed then once 30 minutes of flight time was reached the LED/buzzer would by triggered.

If I understand correctly all you want is a settable timer with an alarm (an off-the-shelf device). Why do you need to read the data stream if you are going to use buttons to set the delay? Just start the timer from zero at the start of the flight.

I assume the OP wants to set a time, say one hour, just once, at a quiet moment and not when there are lots of other things to think about. He will then get an alarm after an hour's flying.

That's correct...also I don't want to have to remember to set the flight duration time for each flight. It will be used in an aircraft that will have very limited fuel supply/flight duration (only around 45 minutes). So, in addition to low fuel warnings, I also want a flight duration warning.

I don't want to have to remember to set the flight duration time for each flight.

Click to expand...

I must be missing something here
Unless each flight is the same duration surely you will have to reset the duration each flight?
An ordinary kitchen timer remembers the set period and can time the same period repeatedly, with a single button press.