Overview:

A piezoelectric valve is used to control deuterium pressure inside the fusor

Deuterium Control(11/15/2015)

Deuterium tank

Deuterium Control(11/15/2015)

Pressure regulator

Deuterium Control(11/15/2015)

Regulator test with Argon tank

Deuterium Control(11/15/2015)

Piezo gas valve(Vacoa MV-100) accurately control deuterium pressure in the 1e-4 torr to >1e-2 torr range

Deuterium Control(11/15/2015)

Swagelok VCR adapters for converting the valve from swagelok tube to VCR inlet and outlet ports

Deuterium Control(11/15/2015)

Deuterium/dry air admit(for venting the core to atmosphere) manifold to attach to the back of the conflat cube, used swagelok SS-4H bellows sealed valves w/ 1E-9 TL/s leak rate

Deuterium Control(11/15/2015)

Gas inlet manifold mounted

Deuterium Control(11/15/2015)

Valve connected to gas manifold

Deuterium Control(11/15/2015)

Prototype gas valve control circuit(80V boost converter and potentiometer)

Deuterium Control(11/15/2015)

Deuterium tank

Deuterium Control(11/15/2015)

Full system view with prototype deuterium control system

Deuterium Control(11/15/2015)

Pressure under manual control

Deuterium Control(11/15/2015)

Feedback control with proportional gain only

An NP10 boost converter, or other boost converters used to drive nixie tubes provides 87V from the 24V supply, then an LR12 adjustable regulator steps the voltage down to 70V to feed the positive side of an OPA445 high voltage op amp which is configured as a gain 21 non-inverting amplifier. A recom RS3-1212D DC-DC converter provides -12v to the OPA445 and an AD826 that is used as an input differential amplifier. The vacuum gauge output(quattro 999, 0-10v, logarithmic to pressure) is connected to the negative side, while a potentiometer supplying 0-12v is connected to the positive side. The valve will now accurately control fusor pressure. There is still some drift and overshoot since it's only a proportional feedback controller, but the final version will be a full PID with valve dither on top of the analog signal to improve performance.

Deuterium Control(11/15/2015)

Pressure control with proportional gain, note drift in steady state level

Deuterium Control(3/06/2016)

Full PID circuit

Deuterium Control(3/06/2016)

PID feedback control with dither injection

Deuterium Control(3/06/2016)

PID control board

The circuit board holds 2 independent PID control circuits, for the gas valve control only one will be used, the version with both in use will be used to control the HV power supply and in injector current. The one connected to the power supply will compare the grid current to a set point and adjust the ion sources accordingly to allow operation at any pressure/voltage/current point with all 3 adjustable independently.

Deuterium Control(3/06/2016)

PID control board

Deuterium Control(3/06/2016)

PID control board, populated

Deuterium Control(3/06/2016)

Controller box

Deuterium Control(3/06/2016)

Controller box

Deuterium Control(3/06/2016)

The control system is now in a complete box,
The controls in the front are(from left to right), power LED and switch, valve purge button and internal/external pressure set point reference, Direct output voltage control pot and direct/feedback control switch, internal pressure set point pot, process variable and output voltage displays

Deuterium Control(3/06/2016)

Controller box

On the back panel, valve output connection, power input, error voltage monitor, external pressure set point, pressure input from gauge

Deuterium Control(3/06/2016)

Output voltage to valve with 6v dither

The final circuit is a full PID controller with output dither, there is a 6v, 90Hz triangle wave superimposed on the output to improve accuracy

Deuterium Control(3/06/2016)

Step response

Deuterium Control(3/06/2016)

Holding pressure over operating range

Deuterium Control(3/06/2016)

Holding constant pressure

Deuterium Control(7/27/2016)

Tank mounted

Deuterium Control(7/27/2016)

Tank mounted

Deuterium Control(2/27/2016)

Permanent tank mounting location

Useful links:

http://www.fusor.net/ Open Source Fusion Research Consortium.

By attempting to reproduce any experiments or devices listed on this domain in part or in whole, you agree to hold me harmless against any lawsuit or liability.

Copyright © 1998 - 2005 by Andrew Seltzman. All rights reserved.