Unicorn Buster – New key-fob version

Some design changes

  • Smaller! Much much smaller, 25mm in diameter.
  • Uses a chip antenna and balun, the PCB antenna and discrete filters where too difficult to tune with the equipment I have in the lab.



Also experimenting with a pogo pin programming jig.key-fob-jig-explode


The PCB’s should be here in a week or so, and I’ll post some more photos when I’ve built one up.

Posted in Hardware Design, Workshop at April 20th, 2014. 3 Comments.

Signal level converter

I built a very simple level shifter circuit while helping a friend build an interface between a Arduino and his house’s alarm system. The alarm system uses 0 -> 12v for signaling.

I’ve tested it down to 1.8v and up to 30v and to about 1 Mhz square waves. You could probably push it higher but the signal integrity degrades quite rapidly.

level_converter_sch level_converter_pcb



Posted in 3D Printing, Hardware Design at February 1st, 2014. No Comments.

Unicorn Buster – FAQ

  1. There are two components to the project. The key-fob uses a nRF8001 proximity Bluetooth controller. The USB dongle side uses a TI CC2540 in a BlueGiga BLE112 module.
  2. The key fob constantly sends. You can turn this off by holding down the button, the button is also used to sync it to a new master. There are two advertisement modes on the key-fob. Fast – for the first 60s after losing connection send broadcasts at 40ms intervals. After 60s this rate drops to once every 60s. Doing this should last about 18 -> 24 months.
  3. The USB side emulates a keyboard and when connection is broken(+ some timeouts) it sends a keyboard command the lock the machine, this can be configured.
  4. OS, all this is developed under Linux, but since it’s just a USB keyboard it works with any machine without additional software (that was one of the original requirements.) There is also a virtual serial port for configuration, probably just going to be a text interface to change config. There will also be a bootloader that will work with avrdude.
  5. I will eventually open source the code and hardware. But I’m not planning to sell this online, might sell to a few friends at the office.
Posted in Embedded Firmware, Hardware Design, Workshop at July 3rd, 2013. No Comments.

Unicorn Buster – Progress

Right a status update!

1. Key-Fob

Built up the prototypes of the key-fob. They turned out OK, there is an error in the switch footprint which was easily fixed. I tested them with the nRF Utility Android App.


2. USB-Dongle

There was a bit of a bugger up with the radio I wanted to use for the USB dongle. I was planning on using a nRF51822, I bought the dev kit and everything, BUT after starting to code up the firmware I realised that it can’t do master/central roles. Yea, helps if you read the data sheet completely.

In it’s place I’ve gone with a Bluegiga BLE112-A Bluetooth smart module and yes I’m pretty sure it can run in the master mode. The BLE112 is build around a TI CC2540 Bluetooth low energy SoC. I need to get a move on with this thats why I went the module route and not implement the full CC2540 layout.



Posted in Hardware Design, Workshop at June 19th, 2013. 5 Comments.

Sneak Peek – Unicorn Buster

I’ve been working on a new project and here’s a sneak peek.

What is the Unicorn Buster? It’s an auto locker for your workstation/laptop, keep the key-fob on your person and if you walk away from your machine it’ll lock.


Key-Fob Case

Above is the key-fob part of the system. I’ll post updates as I finish the rest.

Rigol DG4102 – Unboxing

I’ve needed a function generator for a while now. The Rigol DG4000 series got good reviews from Mike (Mike’s Electric Stuff) and Dave (eevblog), so I got one. Specifically the Rigol DG 4102

Some quick specs:

  • Maximum output frequency (Sine): 100 MHz
  • 500MSa/s sample rate,
  • 14 bits vertical resolution
  • Dual Channel Outputs
  • 150 Built-in Waveforms
  • Built-in 7digits/s, 200MHz Counter







Posted in Workshop at February 26th, 2013. No Comments.

Wiha screwdriver set

I’ve been looking for a set of good instrument screw/torx/nut drivers. I found the following Wiha 92190 Master Technicians Bench Top Set, 50 Piece after watching a TheSignalPath video and Shahriar showed the set he has.

The set contains:

  • 10 Slotted 
  • 4 Phillips 
  • 10 Nut Drivers 
  • 10 Torx Drivers 
  • 6 Metric Hex 
  • 10 Inch Hex 
  • 1 Chip Lifter

You can buy a set from Amazon, http://www.amazon.com/gp/product/B000T9XZFO

They come with a desk stand with enough holes for the 50 drivers.

Extremely nice tips. Everyone seems to say they are indestructible.

Conclusion? A great set of very high quality screwdrivers, they are a bit pricey but I can highly recommend them.

Posted in Workshop at November 25th, 2012. 4 Comments.

MakerBot spool holder

I bought some extra 1.8mm ABS plastic from Netram for the Replicator. Of course it didn’t come on a spool that fits the built in brackets. No worries, I designed my own.


The following archive contains both the STL files (ready to print) and the Solidworks parts if you want to make modifications. spool_mount.tar.gz

Posted in 3D Printing at July 29th, 2012. No Comments.

Makerbot Replicator – Unboxing

So I bought my self a 3D printer. I went with the MakerBot Replicator. Here are the unboxing photos.

Box seems to have survived the shipping process in one piece, maybe the +10 Fragile stickers helped.

All the bits and pieces are packed inside the frame. Luckly everything was accounted for. Pity they don’t throw in some stickers, that would have been cool. Read More…

Posted in 3D Printing, Workshop at July 29th, 2012. No Comments.

IoT Power Monitor


I’ve got a pre-paid electricity meter installed at my new place in Cape Town. It outputs a 1/1kWh pulse via a LED on the front panel. I thought it would be pretty cool to read and log the power consumption of my house. It’s also an excuse to play with WiFi and other fun stuff.

Functional Specification

  1. Microcontroller, PIC24FJ64GB004
    • Low pin count
    • Low power
    • Built in RTCC (needs 32.678 khz crystal)
    • TCP/IP Stack
  1. Power supply
    • LiPo – 2000mAh
    • 500mA Charger
    • 3.3 switch mode buck/boost voltage regulator
    • Battery state of charge
  1. Micro SD card
    • FAT32/16
    • Log data, very simple txt format
  1. User Interface
    • LED, 1Wh pulse, Low battery signal, WiFi status
    • User button, log the time new coupon was loaded
    • Reset
  1. Wireless connection
    • WiFi, MRF24WB0MA, 802.11b/g/n
    • Microchip PIC24 TCP/IP stack
  1. External Interface
    • RJ11 connector
    • On PCB header
  1. Meter Interface
    • Reverse biased photo diode
  1. USB Device.
    • Micro USB B
    • Mounts SD card as a mass storage device
    • Generic serial endpoint
    • Charge battery
  1. i2c Temperature sensor

Design and Schematics

Read More…