AXEtimeter I - model rocket datalogger - part 4


Senior Member
First flights! We're still building a payloader rocket, but it wasn't finished and we were itching to fly the AXEtimeter, so we attached it to the side of the 2nd rocket my daughter built, the Estes Crossfire ISX, and we flew the AXEtimeter three times successfully on a B6-4 engine.

Someone emailed and asked what the white and yellow things are. They are nylon/plastic zip ties. I used the white ones to attach the AXEtimeter to the rocket and the yellow one is just reinforcement to hold the supercap in place. It also presses slightly down on the supercap to hold a black piece of foam wedged between the supercap and the pressure sensor/altimeter. I read about sunlight hitting the sensor and affecting the readings, so I used some light foam to cover it up but still allow it to 'breathe'.

BTW, here's an example of what the serial terminal looks like when the AXEtimeter is hooked up to the PC, powered on, data downloaded, and then powered off.

Starting up...
Supply Voltage = 266 (should be ~2.68V)
Last EEPROM location: 32208
Last Flight #: 3
Altimeter WAI response: [C4] (should be C4)
Altitude: 1593.25 meters, Temperature: 21.6 degC
System Ready!
Mode button was pressed.
Select button was pressed.
Select button was pressed.
Flight data transfer.
Please set terminal to 19200 within 5 seconds.
Beginning transfer:

[lots of data here! snip!]

Transfer complete.
Please set terminal back to 4800.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Select button was pressed.
Initiating power off sequence...
- EEPROM chk=32208
- Skipped update of EEPROM ptr.
- Powering off...
On the first flight, it misdetected the launch so it recorded the rocket sitting on the launch pad for a while, but it got the entire flight. The 2nd and 3rd launches were detected on launch so that's why the data starts after the rocket is already gaining altitude. The first flight reached a height of 106 meters, the second flight was 118 meters and the third flight was 105 meters.

Ready to launch:

I graphed the data for the three flights in Google Charts, but here's flight's #1 and 2:
View attachment 16639 View attachment 16638
I want to redo them in Excel so I have more control on how the labels and such look.

I also need to find a small scale to see how much the AXEtimeter weighs. The supercap alone weighs (according to the datasheet) about 2.3g and it's the heaviest component even compared to the PCB so I'm guessing around 3g total.

When I get a chance, I'll upload video of the launch and recovery.

But now we know how high her Crossfire rocket flies on the B6-4 engines in Colorado (the company Estes is just South of where we live in Colorado!). The box says the rocket is capable of 600ft/183 meters on the B6-4) so either the weather or the additional weight played a factor or heck, my math might be off on retrieving the altitude MSB, CSB, and LSB data from the registers. Anyone wanna check it? It's in the "A" program. We need to try doing the trig to figure out the rocket by sight to compare. Maybe next time. It was a little breezy today, but when we get a chance, we'll try a C6 engine.