The Iron Girl Project - Repulsors, Part 2

For the second part of the repulsor project, I wanted to get data fed back to the main computer while also fading the repulsors in a reasonable likeness to the actual repulsor firing pattern from the movie. So, after playing around with the Trinket, I eventually came up with something like this.



The Thinket fades a 1W LED through a MOSFET in conjunction with the NeoPixel Ring. Here’s my first attempt at getting the audio to work. In this example, the Trinket fires directly and then notifies the RPI via I2C that it’s been fired, and Python plays the pre-loaded sound. This method ended up being scrapped since the delay from the I2C check was too long, and I instead made the Raspberry Pi issue the I2C command to fire the Trinket (which made everything virtually instant).



Below is the Trinket wiring diagram. It’s slightly inaccurate - I’m using a Small Mint Tin Perma-Proto from Adafruit, but they don’t have that in their Fritzing library.

A few notes:

- The center LED is a 1W BL-HP20A Cool White LED. It tops at at 3.8V, but if you use NiMH batteries, it seems to be okay.
- The switchable AA battery pack will feed both repulsors and be mounted on my back. It’s got rechargeable AA’s to make sure the LED doesn’t get too much voltage. I may play around with the center LED power later on, but it works for now.
- The MOSFET I’m currently using (IRF510) is a 10V MOSFET and consequently requires a higher gate voltage than a piddly HIGH on 3.3v. Thus, the center light is a bit dim, but it works. I’m still looking for a suitable choice, and will update in a later post with what I’ve found.
- This also leaves me with one I/O pin, which I may or may not use for a tilt sensor (power-up, power-down)or some other physical sensor to feed back to the main computer.

Next steps? Mount the PCB on a glove-like structure, and figure out proper cable routing up the arm. I'm also alternating working on this with working on the HUD.

Cheers for now,

~Lexikitty