Finished Tesla coil

Tesla coil ready for exhibition.

Short test video of the coil setting paper on fire.

Video from Tesla building

More Tesla build pictures

Tesla coil , a set on Flickr.

We had another night of Tesla coil building. This time all circuits were tested and power applied for the first time.

Laser cut Lego compatible gears

Yes I do occasionally make stuff out of Lego. At some point I got annoyed that i only had up to 64 teeth gears and decided that i could make my own.

 For some other project I bought the excellent Gear template generator from woodgears.ca
After a bit of experimenting i found the parameters for making Lego compatible gears:

Tooth spacing: 3mm
Addendum: 0.350

When machining gears to exactly the measurements produced by the program you get a remarkably good fit.

Tesla 2012

Tesla coil , a set on Flickr.

A while ago i was asked to make a Tesla Coil for an exhibition about Nikola Tesla. I have previously experimented with traditional Tesla coils (Archive). These were loud, dangerous and not really public friendly devices.

A new generation of electronically controlled solid state Tesla coils have been emerging over the last couple of years and we decided that one of these were better suited for public display.

A side effect of the electronic control is the ability to play music. I find this feature rather corny but it seems to be a real crowd pleaser.

Here are the result of the first build night with my long-time Tesla buddy Marc.

Hide And Seek

I have been asked to make a device that allow a space capsule to be found at sea after splashdown. The device should transmit it's GPS position via. VHF radio to a fleet of recovery vessels.
The device should allow regular people without special equipment or training to receive the GPS position.
It was suggested to use plain speech to transmit a WGS84 GPS message that is compatible with most navigation equipment.

This is my initial approach to solving this problem.
First the numbers 0 to 9 and the words "East", "West", "North" and "South" was recorded using a digital recording program (Audacity). The audio file was cleaned and compressed so that the words had an equal voloume and the length was fitted to exactly 32 kSamples. The audio file was then converted to 8bit mono@8kHz .raw format. The start sample and duration of each word was noted.
A special program was made that would transmit the .raw file over a serial port. A 24C256 IIC EEPROM was connected to an Arduino board and a firmware was made to receive the .raw file and flash it into the 24C256.
The EEPROM now contained spoken words that could make up the WGS84 message and a list of starting points and durations for each word.
The firmware in the Arduino board (later to be replaced with custom hardware) was changed to a firmware that received GPS data in the form of NMEA and read these out using the words from the EEPROM.
The micro controller on the Arduino board outputs the audio as PWM which is low pass filtered to make a analog line signal. This signal will later be fed to a custom VHF transmitter that will be integrated as part of the system.

This is a audio test of the system so far. The voice is synthesized but will be replaced by a sexy female voice.

The GPS and audio chip

Active control of payload direction

By changing the set-point of the payload stabilizer the direction of the payload can be actively controlled. This could be useful for panning on-board cameras etc.
In this experiment set point was commanded to sweep between +90 and - 90 degrees with the following profile:

Red=yaw(roll), green=command, 20mS/div.

In the video the payload section vibrates a bit. This is a result of the loop-filter not being properly re-tuned after the motor driver was changed.