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Revision as of 13:35, 15 July 2013 by Bunnie (talk | contribs) (Phage Locator)
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These are projects for phage / BM2013. If you ended up here and you're not part of phage, then fnord.

Phagelings: please record interest at this gdoc

Phage Band

The phage band is a small flexible circuit board that's designed to be soldered in a loop of WS2812 RGB LEDs. It is about the size of your thumb.

It's meant to be a convenient and compact way to make a ribbon of LEDs do something interesting.

As of early July, the board has been sent out for fabrication and should be ready well in advance of BM2013.

The board has the following features:

  • Powered off of +5V via microUSB header (for use with battery packs commonly used to charge cell phones)
  • ATTiny85 for pre-programmed light patterns
  • A single pushbutton to control operation mode
  • If both ends of the WS2812 ribbon is soldered to the board, the ATTiny85 can automatically detect the length of the LED string
  • Microphone and pre-amp with gain control selection (aka "robot heart mode")
  • Flex circuit construction
    • programming header and microphone section can be sheared off with scissors if they are not needed for a more compact driver circuit
    • Steel stiffener plate under ribbon solder point and microUSB header for mechanical robustness

You can download schematics and board layout in PDF format at

Below are renderings of how the board will look:

phageband3.png phageband2.png phageband1.png

Below is what the board looks like after you've sheared off the microphone and programming headers:


Below is a concept of how the board might look mounted into a ribbon of WS2812 LEDs:


Phage Locator

The phage locator is a design proposal. If enough phagelings are interested, I'll complete the design and get them built.

The idea of the phage locator is it's a little "badge" you can wear around. It has LEDs (of course), and it has a "locate" feature. When the button at the base of the board is pressed, an RF beacon is sent out. Any companions in the vicinity (targeting 20-30m range) will pick up the beacon and start strobing.

When not in locate mode, the board cycles the lights, and has a microphone so it can react to sound; although the exact behavior in reaction to sound is still a work in progress (I've got an ATTiny to work with here, not really a DSP giant :P)

Below are renderings of what the board might look like.


There are some components in the white silkscreen region of the head, unfortunately. Physics is a bitch, those were the dimensions of the loop antenna as writ. :P But, I think it's not going to be too intrusive. The head of the phage is also slightly larger than the standard logo; the whole system is sized basically around the loop antenna for making the comms work.


The back reads "PHAGELING [in code 39] / i am infected. i am the phage."


This cut-through of the board nicely shows the antenna loop. Let's hope my calculations work out and the reception is decent!

you can download schematics and layout in PDF format at

Here is the feature summary:

  • Powered off of +5V via micro-USB (compatible with most cell phone battery packs)
  • 6 RGB LEDs around the capsid that can cycle independently as the primary LED mechanism
    • RGB LEDs are controlled by an ATTiny85, so the same firmware patterns programmed on phage-armband can be directly ported into the badge and vice-versa. I was originally thinking about just using the 8051 inside the nRF9E5 to do all the control, but rapidly realized that would suck for people who wanted to make their own light patters. The ATtiny85 can be programmed using an Arduino IDE if you have the correct adapter (see
  • 16 white LEDs around the legs that cycle in a "gang" (i.e., all at once -- using a single boost converter to save power)
  • RF beacon, activated by pushbutton
  • RF receiver - causes strobing action when beacon is detected
  • Microphone to cause lights to cycle in the presence of sound
  • ~4" tall
  • Made out of 1.6mm FR-4 PCB
  • Matte black soldermask with white silkscreen, gold trim
  • Solder tabs that allow you to attach WS2812 light strips to the locator in a permanent fashion. This means you can use the locator as an RF front end for large, fixed installations of LEDs (such as what might be on Strangelove). Because the locator doesn't operate on a loop of LEDs, you will have to burn a custom firmware on that encodes the length of the LED strand. I will have a laptop and a burner with me on the playa, and a system that can touch down onto the programming pads with spring-loaded pins so it should be quick & easy to do field upgrades of the light patterns and behavior.

With a sufficiently modest light cycling pattern, it should last a day on a typical cell phone charging battery pack. Quiescent draw of radio in passive receive + other bits is estimated to be 20mA @ 5V. A conservative light cycling pattern (20% duty on, 50% brightness) will burn about 50mA @ 5V time-average. So about 70mA-100mA estimated current draw, or 350-500mW. A small "lipstick" style cell phone charger pack will have about 9Wh capacity. That's ~18-25 hours run time. Of course, the primary source of current draw is the light pattern. A full-on pattern will draw about 200mA @ 5V, or 1Wh; just idling with lights off waiting for a signal, it draws 0.1Wh. So that's a 10:1 change in runtime based upon the light pattern you choose.

See spreadsheet for update on cost.