Re: PCB designer? Weight issues.

Jared Smith

Brandon -

Thank you for the offer. It sounds like this board is being designed, so that should be taken care of.

To answer your questions though, I'd want anything on the thinnest PCB board readily available for weight savings, though Express PCB looks pretty slick.

I'm going to try out this solar upconverter/charge controller - This should allow me to drop most of my solar cells to feed 1 volt or so to the upconverter which will charge the 5v supercapacitor to 4.2v. And it manages the system power and pulls the plug at 3.27 volts - so I won't drain the supercap overnight and won't get into a start/stop loop with the Arduino at sunrise/sunset. It also has a high/low pin to indicate low voltage, so I could detect this before starting a transmission.

I'd be happy to hear any thoughts on whether you think this is a good idea or if there's anything I'm overlooking. I mostly need to ensure that there's enough juice between the smaller solar cells and the supercap to get through each transmission.

I'm at 5.8 grams for my 9 solar cells, so going to 2 cells should save around 3.5 grams. The charge controller is only .7 grams (around .4 grams if I order the thinner board from OSH Park and assemble it myself), so that's a savings of around 3 grams.

If my first flights work, I might try designing and fabricating my own custom payload boards - one tiny board to handle everything would be VERY small and MUCH easier to put together on a payload - and more reliable too without all of the wiring. This is what most of the very successful (global circumnavigation is a good measure) floating balloons go with. Some are as low as 6 grams (the weight of one US quarter) for the entire payload!


On Wed, Jun 21, 2017 at 12:43 PM, Brandon Tibbitts <tibbs327@...> wrote:
Yes I'd be interested in helping, but have been loaded with quite alot in general. I am experienced some in layout, and should be able to put something together if needed. Unless there is a quicker/easier route that is already in progress, i'd be happy to try though.

Were you thinking of .030 thick pcb or .062? I've used express PCB to get things done in the past and typically just design the board to the size I need, and cut them out, getting multiples out of the fixed size sheets they offer.(PCB 3.8 x 2.5 x .062 thick) The software is all manual place and routing, but for simpler circuits not too bad. Is there a desired connector for J's, or just solder pads to hard wire into? 

There are a couple of newer layout design software packages I've been looking at trying out. Things are rapidly evolving in PCB EDA and multiple open source options. Maybe this would be a good time to try one..

Brandon - KD7IIW

On Tue, 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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