Final Proto, Hardware Lockdown, Buying Shit From China

A project log for Mr Robot Badge

Creating hardware, and 'gonzo trade journalism'

benchoffBenchoff 03/17/2017 at 02:570 Comments

Final Prototype & Hardware Lockdown

This is it. The final revision. Changes from the prototype badge that wasn't shaped like the Mr. Robot mask include the addition of a switching regulator, the addition of battery holders, and a few changes to which GPIOs are used for the buttons. I should have planned for that button thing - it was a floorplanning issue, and should have been taken into account from the get go.

So, what does it look like now?

We're almost done. There are a few *slight* problems with the badge - mashing the buttons resets the ESP, but that's probably because I'm using an SPI port as a GPIO. Should be fixed in firmware. I've edited a lot of the silkscreen on the front of the badge just to make it look a little cleaner.

These completed badges will soon be in the hands of the firmware dev, and everything will be locked down by next week. After that, I need to panelize this board and shop around for a fab. Right now, it looks like I'm about a month ahead of schedule.

Buying Shit From China

Let's use the battery holders as an example of how much you can save by buying shit from China. This is what I need:

It's a two AA battery holder with through-hole solder pins. Here it is on Mouser. It's $1.65 in quantity one, or $0.64 in quantity one thousand. Since I'm making five hundred badges and each badge will have four batteries, I need a thousand. What's $0.64 times one thousand? Ouch, that's $640 just for the things that *hold* the batteries.

Lets see what AliBaba has to offer:

Huh, that's exactly what I need. How much? Fifteen cents apiece in quantity one thousand. Add in $66 for express shipping, and I have a ton of battery holders for a third of the price as sourcing them from Mouser.

Here's a neat bonus: the Mouser variety only have solder pins on one side. The Chinese versions have solder pins on both sides. This does require putting a trace from one positive lead to one negative lead, but it also means a more secure connection to the PCB. I don't have to epoxy this thing down now. Awesome.

Other items of note from China: the LEDs. Each badge has 144 LEDs, and I'm making 500 badges. Do the math. LEDs come in reels of 4000, and the fancy expensive LEDs cost $144 a reel. I need twenty reels of LEDs. A reel of LEDs on AliExpress costs $10.05, a total of $240 for all the LEDs. That's literally a tenth the price.

Buttons, too: I was prepared to spend about $1500 for the proper name brand Panasonic buttons. $90 on Aliexpress got me all the buttons I need, and they're good enough.

Remember, this badge is only designed to last for three days. I can afford to cheap out, especially since I don't need to worry about anything complicated like 'technical support' or 'a good product'.

LESSON: Holy crap electronics are cheap in China.

Where we go from here

Panelizing boards, sending them off to the fab, buying a whole lot of components, and getting them assembled. I'm ahead of schedule and right now under budget.