LARP Tech… Go!

Though I am not an avid LARPer, save the occasional 24 hour Zombie Nerf gun game, I have been working with a friend to add a bit of Tech into the weapons and artifacts that are commonly used. You may have seen the War Hammer project, but we wanted to try and make some more basic options that just add lighting and some feedback.

This was a good first application for the LEDiva chip that I have been designing. It is low power, easy to install, requires no programming, supports many colors as well as modes, has built-in hit detection using a vibration sensor, and rather inexpensive.
wp-1454693256339.jpgSo here is a rundown of the hardware:
1 LEDiva LED driver
The chip uses an ATtiny 85 in conjunction with a vibration sensor and two buttons to send signals to any WS2812B, NeoPixel, LED. Power is supplied by using a standard JST connection from a standard or Lithium Ion rechargeable battery. The LEDiva runs on 5v to 3V power.

1 Rechargeable 1200mAh Lithium Ion battery

1 USB Charger for the Lithium Ion battery

64 WS2812B, NeoPixel, LEDs from Adafruit

1 Molex locking connector – 3 pin female for the LEDs

wp-1454693230730.jpgI have split the main LEDiva code up for this chip so that it has only a handful of game related modes along with what we are calling the Rave Mode. The main mode glows dim until the sensor detects a hit and it lights up brighter.

One of the most important features added was the Brightness setting. By pressing and holding one of the buttons while turning on the ax, you can make the LEDs brighter or dimmer. This setting stays the same until you change it again.

This was a test drive, but once I have everything worked out I will be making more of these kits for LARPers and Cosplayers. The chip itself will be $15 and you will just need to add LEDs and a battery. I will have those available as well, but will mostly be marketing the LEDiva chip. To give an example of how much a full package would run you, the ax uses about $60 worth of hardware.

Electrical draw test for LEDiva

Jon did a power draw test with the LEDiva tonight and here are the results.

The board alone draws 11mA
8 LEDs set to the lowest brightness and white (100% RGB) draw 15mA
Same 8 LEDs set to the max brightness and white draw 300mA

So, on low, each LED draws about 0.5mA
On high, each draws about 37mA

So a strand of 60 LEDs consumes 2231mA per hour at Max brightness and the worse case scenario.


30mA per hour on the lowest brightness and worse case scenario.

I got my birthday presents today…

Well, everything except for the goggles, but they are on the way.

Mini Necronomicon




I got me a mini Necronomicon :)

Coding for the LEDiva

Tonight I got some real headway on my small LED driver. I added the ability to change the number of NeoPixels that are displayed, then update the onboard flash memory so that the ATtiny remembers what you selected even after a power cycle.

So now if you press and hold either of the two buttons, then turn the board on, it will let you select the number of LEDs to use. Just press the Color or Mode buttons to add or remove an LED address.

Q: why would I want to change the number of LEDs that I am using on the fly?

A: Basically, the LEDiva is intended to be a generic all purpose NeoPixel driver. You could use 140 NeoPixels, or just one. Some of the animations, like colorWipe();, start with the first LED address and loop until it gets to the last LED, as defined by the number of Pixels the NeoPixel library was told are available on startup. There is no way for the LEDs to tell the micro controller how many of them you just connected. So the animations will just run all the way out to 140 LEDs be damned. This can slow things as down if you are only using 3 physical LED. To fix this I simply tell the NeoPixel library that I want to use all 140, but make it so that the loop that updates the LEDs stops when it reaches the user defined number of LEDs.

So if you use the new sequence to tell the LEDiva that you want to use 3 LEDs, it will only loop LED updates 3 time rather than 140. Now that I have added storage to the EEPROM, it will remember the number of LEDs you selected the next time you turn it on. Are it and forget it.

Here is the latest code I have:

Now I just need to save the color and mode to EEPROM, but I will save that for another day :)

Watch “The LEDiva project update 12/29/2015” on YouTube

LEDiva rev A sent to FAB

Yesterday I sent a new revision of my drop-in NeoPixel board, the LEDiva, that included the new service mounted battery connector as well as a six pin programming connection.


This is the first step in getting the chip as small as possible. The next revision will replace the through hole version of the ATTiny 85 with a surface mounted version. After that, I will try to add a charging circuit to the board so that the battery can be charged via micro USB cable.

I do still need to work on the firmware to save data to the EPROM so it will remember the last color and pattern selected on startup. I have also thought of a way to select the number of LEDs that are being used so that the more elaborate animations look better.


The LEDiva is made to be used with up to 140 LEDs with unique addresses. Since I am mostly just going to sell the controller board, I do not know how many LEDs any one person will be using. So I will like have the default LED number set as 30, then create a scenario were you can use the two buttons to turn more LEDs on or off. Once you exit the LED selection mode, it will remember the number of LEDs. The sequence will likely be something like; press and hold one of the buttons on startup, then press and hold both buttons for 5 seconds to lock in the new settings.

I will do a video of me assembling the first rev A board when it comes back from OSH Park.

At Emily’s sister’s place for Christmas hot pot.

Committing to Linux

While I do still require the use of Adobe products, I have decided to start using a Linux laptop for my development stuff. I have used a few flavors of Linux off and on for various projects, but never for long enough to be super familiar with the one and outs like I am with Windows. So, off I go… more as this adventure plays out.


Watch “Happy Holidays from Make:” on YouTube