LabView

25 04 2010

Last night I controlled the fusor from LabView. I put together a simplified version of Andrew Seltzman’s Marc III controller. So far I can:

  • graph the chamber pressure in realtime
  • enable/disable fuel
  • set the fuel flow in SCCM
  • see actual fuel flow rate from mass flow controller
  • enable/ disable high voltage
  • set frequency and duty cycle for high voltage

The HV duty cycle lets us do fusion trials without melting the grid.

Something I’ve noticed: when the plasma becomes unstable and sparks… it crashes the data acquisition card. I’m guessing the sparks are creating powerful EMFs. We may need shielding.





10 Caps

21 04 2010

Fabricated the second row of capacitors. I have one capacitor left…so we can take it to 11 when the time comes!

Also received the capacitor clamps to make mounting easy:

And finally got 2A fuses for the power supply:

In other news, I got Windows XP running on my macbook on a separate partition. Also got LabView installed. More on that later.





SCR Test Fire

18 04 2010

I successfully fired the coil power supply’s SCR today. Here’s how: I started by grounding the chassis:

Later inspection revealed less then fantasic electrical conductance between the ground cable and the aluminum chassis.

Wired up the SCR and polywell coils:

For the triggering circuit I improvised with available parts. I settled on this circuit:

Looks like this:

I tested it out and it works!

When the SCR discharges you can see the coils flex and hear a sound from the SCR… and the voltage across the capacitors drops sharply. I took it up to 400V with 5 caps.

Pretty major step forward for the coil power supply.

Nest steps include:

Making a front panel with master power switch, AC indicator, capacitor  bleed switch, high voltage LED indicator.

On the back panel: IEC C14 AC connector, screw down terminals for coils power out, and D-sub interface for computer control (via DAQ). I want to computer control the AC power, bleed resistor and SCR triggering.

Stuart made a keen observation about a relay on the DC side: Relays have a much lower voltage rating for DC vs. AC. So a relay rated at 240VAC may only be rated at 30VDC. This is because DC sparks are harder to quench-  they don’t naturally drop to 0V like AC does. So long story short – I’m going to put the relay on the AC side of the transformer.

I also want to fuse the AC and DC sides.





Call for Schematics

17 04 2010

To the highly involved readers:

Anything you can design and spec (I’m talking schematic and mouser part numbers)…

I can purchase and build.

So if you ever think: “man, famulus should build  X right now”

Send me schematics and part numbers. Provided it’s pertinent to the research and within the budget… I will build it.

——————————————————

Here is a my first schematic challenge:

I just purchased this trigatron for discharging the mega-capacitor:

Here is the schematic for it’s use.

Here is the challenge:

Design a modern version of the triggering circuit shown in this schematic. ie, without using a “break-modulator valve”.





Small Steps

14 04 2010

I mounted the sheet aluminum on the 80/20 chassis:

And installed the new ground cable:





Coil Power Supply Progress

13 04 2010

I cut the bus bar to length, and clamped two bars together to get good hole alignment. Then measured and center tapped:

Drilled and mounted:

Wire it up for a test charge. This time we are charging through a 1KΩ 50W resistor network. Everything seems to work as expected.

Wired up the protection diode:





A Day in the Lab

10 04 2010

Excellent day in the lab.

I got the elevator key copied, so I’ll never get locked out of the lab. I did a successful test of the mechanical relay.

I rearranged the equipment rack to make room for the coil power supply:

Using 80/20 I constructed a 4U rack mountable chassis for the coil power supply:

Next I mounted the electrical hardware on the sheet aluminum. I started by using a transfer punch to make guides for the drilling. Then I drilled and tapped the holes for M3 bolts:

The first circuit I wired up was the 2 KΩ bleed resistor. Here you can see the bleed resistor wired to the capacitor via a switch. Turning ON the switch bleeds the capacitor:

Next I wired the DC side to the capacitor while minding polarity. Put a voltage meter across the capacitor:

Using the variac I slowly brought up the capacitor to 300V:

Once the capacitor is charged… it holds its charge without much dissipation after the variac goes off.

I was planning to power the relay using this ATX power supply (24V across +12V and -12V):

But during my initial testing it started squeeling and soon blew its fuse!

There was no short circuit that I could see, so perhaps it just died of natural causes?

Anyway… it reminds me: I should fuse the  coil power supply before I go much further!








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