Re: PCB designer? Weight issues.

Jared Smith

You'll have to solder:
- Headers (if you want them - I'll solder wires directly to save the weight)
- 2 capacitors (SMD)
- 2 resistors (SMD)
- The TCXO clock (small, but only 4 corner pads)
- The Si5351A. It's VERY small (only 3mm) and has 8 legs, so is likely to be a tricky solder. I've ordered a finer soldering iron tip!

This photo gives a good sense of scale for the components - The TCXO and Si5351A are the two components between SCL and CLK1.

You can see how with only these few components that the board could be very small and light. Jason should have the PCB design done soon.

I think I'm also going to swap out my supercapacitors with this one - It has lower capacitance (1.5F vs 2.5F), but saves a full gram of weight.

I think with these changes I should be pretty close to my target of 16 grams.


On Tue, Jun 20, 2017 at 9:50 PM, Kevin Reeve <kevin.reeve@...> wrote:
So how many components must you solder on this new board he will upload to oshpark?  

Sent from my iPhone

On Jun 20, 2017, at 4:35 PM, Jared Smith <jared@...> wrote:

As a quick update, I've been working with Jason from Etherkit and he's designing a breakout board for the clock generator - It should be MUCH smaller and lighter than the existing board - I'm thinking at most 2 grams (if you don't add the headers and wire it directly).

He's going to upload to OSH Park after he's designed the PCB and I'm going to order at least a few soon. Is anyone else interested in some? Gary?

Now I'm considering designing a breakout for a small solar charge controller so I can use fewer panels. The idea is to charge the supercapacitor with the minimum number of solar cells possible while also ensuring that there's enough juice to get through the 2 minute transmissions.


On Mon, Jun 19, 2017 at 6:01 PM, Jared Smith <jared@...> wrote:
He's not, but I've copied Brandon on this message to see if he's interested, or if he'd like to join the list -

I think I can figure out which components can go away on the Si5351A board and order a prototype, but this level of electronics is definitely not my specialty.



On Mon, Jun 19, 2017 at 4:30 PM, Josh Jensen <kd7wrc@...> wrote:
Is Brandon Tibbetts on this list? He's done some PCB design work before.


On Jun 19, 2017 16:14, "Jared Smith" <jared@...> wrote:
D'oh. Hit Send a bit too early.

Anyway... I could go from 9 to 4 (maybe 3 or 2) solar cells with a SPV1040 step-up converter / charge controller - - (or similar) to charge the super capacitor to 5 volts. It would take a bit longer to charge it, but it should maintain the charge long enough for the regular transmissions. This would also need a custom PCB (at least I can't find an existing charger breakout board that is in the 0-2 gram weight range).

If I could pull off both of these adjustments, that should put my payload well below 15 grams which would be optimal for a higher altitude float.


On Mon, Jun 19, 2017 at 4:06 PM, Jared Smith <jared@...> wrote:
Does anyone have experience with PCB design?
My balloon payload finalized, I'm now at around 20 grams or so. This is 5 grams heavier than I want for optimal altitude. I can lose unnecessary resistors, etc., but this might gain me at most 1 gram.

My heaviest component by far is the Si5351A breakout board at 5.3 grams - You'll notice that it's on a thick PCB, it has 3 outputs (I only need 1), and it has 5v to 3.3v conversion on-board (I'm strictly 3.3v). 

It should be 3.3v and one output only, with header and edge mount SMA pads. On a thin PCB, with 3.3v only and one output (header and edge-mount SMA pads), I think this could come in at 1 gram or less. I think this would be a very popular board that you could make some $$$ off of.

Is there anyone here or do you know anyone that would be interested in this. I'd fund the prototype boards, but need someone smarter than me to do the design. I have the full PCB design files and schematic for 3 different 5v/3.3v boards that would get you most of the way there.

Another possibility to lose weight is to most of my solar cells and add a solar upconverter/charger. It takes 9 panels to make 5 volts. They're very light weight (I think 4.5 grams for the full array - plus I need some infrastructure to keep them in place), but with a 

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