Search found 996 matches

by Daniel Wee
Sat 11 Dec 11 2010 3:13 pm
Forum: Space Balloon Project
Topic: Barometric altitude computation
Replies: 3
Views: 18298

Re: Barometric altitude computation

Accurate derivation of absolute altitude based on the ICAO standard atmosphere requires the ISA model which is published in ISO 2533-1975 and the various addendums of 1985 and 1997. Unfortunately, this doesn't seem freely available on the net. http://en.wikipedia.org/wiki/International_Standard_Atmo...
by Daniel Wee
Fri 10 Dec 10 2010 11:06 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

I think I'm going with the LM2842X/Y for the 3.3V switching PSU. I will need a reference voltage source to track stuff.

Daniel
by Daniel Wee
Fri 10 Dec 10 2010 10:12 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

Given that we need 9V for the RF module's power amplifier and the nominal current draw is 0.35A (probably less), we can now compare whether a linear or switching supply (assuming 82% efficiency) is more efficient. For the linear supply, taking a nominal input voltage of 11V, the power lost is:- (11V...
by Daniel Wee
Fri 10 Dec 10 2010 9:58 pm
Forum: Space Balloon Project
Topic: Balloon Volumetric Calculations
Replies: 6
Views: 24421

Balloon Volumetric Calculations

The tricky part with accurately calculating the balloon volume has to do with the elastic force. The other parameters we should be above to estimate - pressure and temperature. We also know the gas density's relationship with temperature. As such, using Boyle's Law, we can work out the volume - but ...
by Daniel Wee
Fri 10 Dec 10 2010 9:45 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

Yes but we may not be able to recover it within one hour. So I'm just planning for a big margin.

Daniel
by Daniel Wee
Fri 10 Dec 10 2010 6:22 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

The RF module draws a maximum of 380mA at 9V and typically 350mA. Assuming that we just went with a linear off 3S, we would end up with about 3.85W input for 1W output. Also, assuming a 64-byte packet at 1200baud, this will require half a second or so to send. If we send the data once every second, ...
by Daniel Wee
Fri 10 Dec 10 2010 6:04 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

At this point, we need to determine exactly how the sensors will be mounted, how many, and what type. This is for board and power supply considerations. One of the sticky points now is the 9V required by the RF module in order to output 1W. At 5V, it is going to be putting out much less than 500mW w...
by Daniel Wee
Fri 10 Dec 10 2010 5:57 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

SD card interface

The SD card can be accessed via the SPI interface. The following link(s) are useful references:- http://www.k9spud.com/sdcard/ http://www.k9spud.com/sdcard/schematic.php http://www.brushelectronics.com/index.php?page=software http://mondo-technology.com/sdcard.htm http://www.captain.at/electronics/p...
by Daniel Wee
Thu 09 Dec 09 2010 7:24 pm
Forum: Space Balloon Project
Topic: Cygnus Module development
Replies: 20
Views: 55766

Re: Cygnus Module development

The GPS itself can sit under the foam shields and should operate without issue. This will allow it some heat shielding but it would be crucial to test the operational temperatures for this module. Power wise, I'm trying to see how little power I can get away with for the entire system. The real pinc...