Manufacturing guy-at-large.

Public Radio Progress

Added on by Spencer Wright.

The last few days have been a bit of a whirlwind. 

First, we visited Todd to discuss some circuit layout concerns. On the way over we nabbed a cheap radio at RadioShack, and took it apart with Todd.. 


What we found was really interesting. The device uses a different chip than we had been prototyping with, and as a result their circuit is *much* simpler. Our chip (Silicon Labs' Si4703) requires digital tuning, which we were accomplishing with a microcontroller. But RadioShack was using the Si4822, which is mechanically tuned. The result is drastic from a circuit standpoint - they no longer need a voltage regulator, or a microcontroller, or a bunch of additional passive components on the board. They're also in a better position re: noise on the board: an MCU (and a voltage regulator too) will produce a bunch of noise that might get on the antenna, affecting reception. RadioShack doesn't need to worry about this at all.

Over the past few weeks, we've been looking for just a breakthrough like this - a way of rethinking the problems we were dealing with. Our issue was that we were stuck conceiving this as an Arduino-descended product, which it doesn't need to be. 

public radio hammer nail-1.jpg

We also made a bit of progress reengineering the hardware layout of the board. Our new design (this is just the board layout, not the circuit schematic) will be significantly easier to assemble, program & service.

public radio hammer nail-2.jpg

We're also pretty sure we can shorten the antenna *significantly.* The mockup here shows a custom solid stainless steel antenna, 50mm long. I rather like it, and it's designed such that a longer telescopic antenna can be swapped in easily. 

short antenna round pcb full assy.jpg

Our PCB will now be circular, and we're soldering the potentiometer and speaker directly to the board. There will be a bunch of SMT stuff on the top (same side as the speaker & pot) and a battery back and trimpot (not shown) on the bottom.

I *really* like where this is headed. More updates soon.