I've spent sort a lot of time figuring out how to print and polish metals. Just because it's neat. There was a LOT of trial and error, and very little actual material I could find reliably, so I hope this log helps any others (or future me) reproduce the results.


  • ProtoPasta has the best (sturdiest) material, but ColorFab's stuff polishes better. These will be softer than PLA but sturdy enough for decorative use.
  • Virtual Foundry Filamet can be sintered for a SOLID, ALL-METAL part. Print at 30mm/sec, dial it in for your printer. 100% infill if possible
  • Coconut charcoal: ~1" in the bottom of a cup, then cover the part with 1-2" of coconut (cf: Hadar's instructions).
  • De-bind with VF's process (1st three steps below, but use h1: 0)
  • Sinter at 1580* for at least 4h for small parts (<5mm at the thickest/widest) Longer hold time will consume more coconut, so use a taller vessel / more nut.
  • Allow to cool in place / slowly. Once it's well under 700F you should be able to remove it from the coconut.
  • I'm still learning about sintering, but I THINK there's a pretty narrow range of effective temps (like 1530-1580), and the MBP or coconut seem to insulate VERY WELL. So holding for a very long time will produce a more thoroughly-sintered part

3D Printed Fidget Spinners

I got these designs off of a site called http://www.thingiverse.com, where you can design templates and share them with the public, or download someone else’s. If you have a 3D printer, I highly suggest you use this site. I managed to find some designs and press the bearings and/or steel balls into them. Enjoy!

Shark fin spinner- http://www.thingiverse.com/thing:1936727

Triangular spinner-http://www.thingiverse.com/thing:2126470

Steel ball spinner- http://www.thingiverse.com/thing:1821445

Shark fin spinner Triangular spinner Steel ball spinner

Spinner w/ shark "fins" Spinner shaped like a triangle Spinner w/ steel balls for weights

Spinner model

update: I stopped development on this project, for a few reasons:

  1. cost
  2. functionality
  3. flexibility

The handset unit fits in a Nintendo Nunchuck. Assembly is straightforward, but involves a dremel and a lot of relatively fine soldering. Nunchucks cost $10, and the remaining components are about $30-50 in small quantity: LiPo battery ($5ish), radio ($2-5), mcu ($10-20), BMS ($5-10), LED & discrete components (<$1). They take about 1-2h to build. Performance is as good as or better than the Nyko wireless unit. I ultimately made functional prototypes with the NRF24L01 chipset (inexpensive and easy to program) and a 433/915MHz radio (harder to find and program, but better range).

The receiver end is much simpler. It's about as big as wiiceiver, costs about the same ($20 + radio), and is about the same difficulty to produce -- 20-60 minutes of assembly and soldering.

Functionality: as a 2-axis remote it works great, but one of the target applications was for a surfboard. 2.4GHz doesn't penetrate water well at all, so I went to 413/933MHz radios. They work, but still not great through water.

Flexibility: Libraries for the NRF24L01 and 433 / 915MHz radios are *significantly* different. Enough that it's not practical to use one software stack for both.

Based on the combination of the above factors (it's expensive, hard to make, and can't easily support cheap/plentiful radios) I've stopped development. It was a cool project though!

note: working title

Wiiceiver has been awesome -- it lets people use an inexpensive wireless nunchuck + standard ESC to drive their skateboard. But the internet is running out of nunchucks, and there are some features still missing.

Wiiceiver X is a two-module system, controller ("Chuck") + receiver ("Board"):

  • wireless, ergonomic, rechargeable handheld controller w/ battery status
  • receiver module with battery disconnect, current & voltage measurement, and servo (ESC) output.
  • fully hackable: exposed pins on both units, standard NRF24L01+ transmitters, simple bidirectional communication

Wireless Chuck features:

  • LEDs for board battery status
  • configuration interface for the receiver (same as Wiiceiver's configuration routine)
  • channel bonding & checksumming for managing cross-talk: board <-> chuck will share a provate channel, up to 100 channels available

Receiver / Board features:

  • LEDs for management / troubleshooting
  • channel bonding to a chuck
  • on/off ESC power management & voltage monitoring
  • up to 4 ESC outputs (any can also serve as BEC connector)


  1. When will it be available?
    • I don't know, I'm working on it now. Probably $75
  2. How much will it cost?
    • see #1
  3. Can I install it in my own skateboard / go-kart / unicycle project?
    • Sure.

Mommy's golfcart doesn't have a usable fuel gauge (battery level meter), or a clock. I have fixed that.

Dash, clock offdash, clock on

I slapped an Adafruit OLED (same as on my skateboard) onto a Particle Photon. I used a simple voltage divider to split the ~56v battery string down to something measurable, and a 48V relay to turn on/off a lower-voltage (~18V) line to power the voltage regulator.

The Photon awesomely has a very simple battery backup connection (so there's a lithium battery in there too), and the clock awesomely syncs up whenever it finds the cloud.

clock view

The display currently shows a fuel gauge bar, under that it has raw ADC value (debugging), a calculated voltage level, and a symbol showing the device's state of connectivity -- z (sleeping), + (connecting), * (connected). The device doesn't like being disconnected generally, so I detect that state and disconnect manually. It will reconnect on power-up, or if it senses the cart being charged (e.g. in my garage).

The clock display uses the built-in font, has a blinking cursor (currently "off"), and a smaller seconds display (also for debugging).

The code is a little silly, but please This email address is being protected from spambots. You need JavaScript enabled to view it. if you want to try and make one, I'll hook you up.

Tell your device what to do!

Turn the LED on.
Turn the LED off.

1.95x2.00 inch (49.53x50.80 mm) 2 layer board.

A new hardware project: Crazy Volts. Drew and I are working on a fuel gauge for his Crazy Cart. It's based on the ATmega328P + Adafruit's OLED display, and a custom PCB to hold it all together.

The power switch for the cart has 3 leads: ground, battery, and switched to controller. The controller lead is switched and provides the voltage sense, so we just wired the input + power leads together. The display running in the pic above shows our calibration test, and the display itself hasn't been permanently mounted yet.

The design is general enough to be adapted to anything with batteries. In software we'll probably only try to estimate the power characteristics of SLA, but it's just software....

2 layer board of 1.55x2.05 inches (39.47x52.15 mm).

We also considered using a general-purpose ATmega328 breakout (the bduino), or a teensy 3.1 + adapter board to wire up a regulator + OLED display.