Pecan Pico 4 – Serial Number 1 Built & Working

A new Pecan is born! I’ve received the PCBs within a week from Seeedstudio but I had to wait for a delayed delivery from digikey. I’m not really happy with the delivery times from digikey but I guess I need to blame USPS for this. I need to order from them though, because they are the only reasonable supplier for BMP180 and the GPS chip antenna. Anyways, I built up my first Pecan 4 and it worked out of the box. I was surprised that the code written for BMP085 immediately worked for BMP180 without any code changes. I still have to write some code for the RGB sensor, the EEPROM, the RTC and the beeper, but everything that worked at Pecan 3 is also working on the new PCB.

Edit: The Arduino Code and the Eagle/gerber files are on GitHub:

BLT33.3 Launch From Pelican Island

To make it short, many things went wrong on this flight. Due to a delay in parts I was only able to build the PecanTurbo amplifier and the CW beacon on Friday evening before launch. I did get this working, but there was not enough time left for proper testing. It turned out that the PecanTurbo did quite a good job amplifying the signal, but it also jammed the GPS receiver.

When I tested this in my house I noticed already that I could only get a GPS lock when there was far enough distance between the transverter and the tracker. Therefore I decided to make two separate payload packages. At the launch I first started the tracker and almost immediately got a lock on the GPS. However when I started the transverter I didn’t verify that the lock was persistent. Apparently it was not, therefore we didn’t have GPS coordinates throughout the flight.

I tried to make another “improvement” a few days before launch was to re-design the pressure altitude formula from empirical data I’ve collected on a previous flight. Also something you can’t test unless you have a Cessna available. I have simulated the formula with old flight data in a spreadsheet, but I couldn’t verify if it was accurate in the actual C code. The stupid error I made was simply that I converted meters to feet, but my pressure altitude formula returned already a value in feet. This didn’t make much difference at altitudes near the sea level, but at high altitudes the number was off by a factor of 3.28.

The park warden chased us away from the entry building so we had to fill the balloon at high winds at the parking lot. This made any weighting attempts pointless (though I had a scale in my trunk). Despite of those difficulties we’ve filled the balloon with enough helium and the lift off was very nice.

Thanks for the video from Rp White!

The burst happened around 101 kft (calculated from the pressure telemetry with a pressure altitude calculator on the web) and from the prediction (see my previous post) we estimate that it landed East of Galveston Bay.

On my way home I took the free Galveston ferry and made a long loop around Galveston Bay  receiving any APRS signal I could pick up in my car. That area is almost uninhabited and of course there are no digis or igates in a 30 mile range. Even with my 11/8 vertical on my roof and 20W power I was only picked up in a few spots. Therefore I guess a 100mW PecanPico3 has no chance to be heard.

Our only last hope is that a hunter of fisherman will find the labelled Styrofoam box and call us…

Some photos from K5SAF