Sunday, 2 October 2011

High voltage supply: some progress

** DISCLAIMER - Unless you know what you are doing, dont try this.  This blog post does not contain enough information to try this safely. **

One thing on my project pile is to construct a HV supply, suitable for use in Kirlian photography and similar experiments. An extremely simple circuit can be used to generate reasonably high voltages from an old flyback transformer.

Some first experiments generated pretty arcs, and showed that it might work.  I made a bit more progress now.  The supply is now contained in a box, to keep stray fingers out, and it contains a rectifier, so it can be fed AC power.  Thus, it can be powered from a variac.  This is a nice source of adjustable power, and it will prevent me from blowing the lab supply with this thing - its a really ill-behaved load for any supply.

Heres a pic of the setup.  The HV supply on the left, variac on the right.  Yep, definitely time to put the variac in a case.
And a classy warning sticker. 
With just 7V AC in, i'm getting some nice arcs.  The effect of arcing into a cup of water is quite interesting, but this picture doesn't do it justice really.

At this point, raising the voltage much more leads to unwanted arcing, such as this one from the HV wire to the case. 

A bit more fiddling, and it will be time to try some Kirlian stuff.

Saturday, 17 September 2011

Oatmeal making robot

I like oatmeal, the real irish steel-cut kind.  But, it takes a half hour of slow simmering in milk, and you have to stir it continually, or it will stick and burn.  Its the 21st century - aren't robots supposed to do the boring jobs for us now.
Thanks to notbrainsurgery for figuring out the protocol and posting sample code for controlling the robot. (Details here)

Sunday, 11 September 2011

3-Digit LED display with Arduino

There were some 3-Digit LED displays lying around to play with.  So i hooked it up to an Arduino for fun.  There are 11 lines - one for the positive for each digit, and one corresponding to each segment.  Thus, unless you want to display the same thing on all three digits, you must switch the configuration faster than about 60 Hz. 

If hooked up directly, it uses up 11 lines of the Arduino.  But with a 74595 shift register to expand the output, this can be reduced to 4.  You still have to run a fairly tight loop switching the pins, so it kind of uses up the controller.  On the other hand, this would easily run in a very small controller so it still might be useful.

The scope shows the serial line.  The arduino is merely counting up every 100ms.  Circuit and code to follow eventually.  More coffee is needed first.