Re: My floating balloon plans

Jared Smith
 

You mentioned that you need a micro USB cable for programming. I don't know if they've changed the FTDI breakout board or not, but the one I have has a mini USB.

The one I got from Amazon is micro USB. It also has a jumper to change voltage between 5v and 3.3v. Sparkfun has a mini USB version (https://www.sparkfun.com/products/9873) and a micro USB version (https://www.sparkfun.com/products/13263).
 
Speaking of my pro mini with screw terminals, how are you prototyping? Connecting the pro mini to the breadboard, or using an uno? You could borrow mine if you want for prototyping. It is a 5V version though. 

I'm using a breadboard for prototyping. I also have an Uno, but the voltage difference would complicate things.
 
Depending on where you come in for weight, you might want to consider pulling unnecessary components off the arduino. You can get by without the reset button and the LED along with its resistor. It won't be a lot of weight savings, but when you're talking grams it can all add up. I couldn't remember if I mentioned it or not. 

Yes, I may do this. I'm using the onboard LED to indicate status (lit if there's a GPS lock and flashing while transmitting), but that won't be necessary at 40,000 feet. :-)

The biggest weight savings would be in going with smaller supercapacitors. Going from 5F to 3.3F would save 1.2 grams. But having two in series to make 5.4 volts also cuts the capacitance in half. I'm going to test a lot to see how much of a difference it makes, but think I'll probably go with the smaller ones.

The Si5351A Clock Generator board is also rather heavy - I think ~4 grams. It has voltage switching/regulation and 2 extra outputs that aren't necessary. I'm going to look into another option or maybe trying to design a small custom breakout board with only one output. That would save around 2 grams.

Thanks!

Jared

 

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