Moxtek X-Ray Tube Controller - Part 3 - Enclosure

Finally, I got around to make an enclosure for the Moxtek X-Ray Tube Controller with a proper control panel.

The complete "X-Ray Tube Commander 2000" Controller in all of its glory.

 This enclosure might be further improved with an angled front panel at some point if I get too bored but for now it serves the purpose.

The faceplate text is currently done "quick-n-dirty" style with a Label Maker but I'll print a nice colored laminated front decal for it to get the more refined "lab equipment" look, just the way I did with my N2PK VNA.

The front panel component mounts include large LCD display, 2 backlit control buttons, a rotary encoder /w button, a keylock and a small speaker grill.

I designed the enclosure with TinkerCAD - this application is excellent for simple projects such as this one, and it is very fast to work with.

Once the measurements are taken, it literally takes minutes to create the design and output the STL file for printing.

I made the bottom part of the enclosure a bit taller than necessary, just to have some spare room if I decide to change things around or add more connectors on the sides. Since it is a just a piece of benchtop equipment, the size is not critical.

 If I ever do another print of this, I will definitely make the box slimmer, round the corners and angle the front panel. 

The X-Ray Tube Controller PCB and components, installed in the enclosure. 

A "Window" on the side exposes the edge of the PCB where all tube interface connectors are located - a DB-9 for connecting to the tube's HV module, supplemental power connector for tubes working at higher power levels (>4W), terminal strip with all interface signals to external devices (test enclosure interlock switch, illuminated warning sign, etc.)

I used this window to feed thru temperature sensor cable, but I will drill and mount a proper 4-pin connector at some point.

The keylock is part of the X-Ray safety protocol and prevents from engaging the beam without a key. These types of X-Ray tubes create an incredibly high flux right at the aperture and when setting up a sample for XRF the user should turn and remove the key to prevent any accidents.

 In addition, the XRF enclosure door interlock switch is in-series with the keylock so the control key must be turned to "ON" AND enclosure door closed for the beam to engage. A very serious X-Ray hazard is not only the direct exposure to the beam but also from scattering. Even air scatters and reflects X-Rays so no tube operation should be done without proper shielding. 

The yellow MODE Button serves multiple functions depending on the context.

Single-press is RESET (for Timers, errors, time logging and also acts as an "Emergency Stop" while the X-Ray beam is ON).

 Long-press changes beam operating modes and a double-click switches between the 2 memory presets. 

This button also acts as a "SHIFT" while tube operating parameters are dialed in with the rotary encoder (for Timer and Min High Voltage). Holding the MODE button down while pressing the Encoder button will toggle ON/OFF the Tube Error Check feature.

The yellow LED in the MODE button is a "READY" indicator showing that the x-ray beam can be engaged - it turns off if the current conditions disable the x-ray tube - during parameter entry, filament cooling stage or errors for example.

The push-button on the Rotary encoder is used to enter Parameter Setup mode and scroll thru the different digit positions while entering the value. 

Tube and Controller Parameters are then dialed in with the rotary encoder at the position of a blinking cursor. 

This button also serves as an "Emergency STOP" button in Timer or Toggle modes, instantly and unconditionally terminating the X-Ray beam.

When the beam is ON and operating in Timer mode, the rotary encoder can be used to add or remove time from the currently running timer by simply spinning the knob.

The BLUE button is exclusively used to operate the X-Ray beam (according to the selected mode).

The blue LED in this button indicates if the beam is ON and it also flashes with 1 Hz period while the Timer is running.

The status line on the display will show the status of the "Filament heated" signal returned by the tube with a message "X-RAY ON!"

On this picture, the status line displays "Tube ERR!" with Error Code E-111 due to operation with disconnected X-Ray tube.

I also added an option to temporary disable the Tube Error Check.

The 3-digit error code is very easy to read:

First digit on the left shows the state of the "Filament Ready" signal, returned by the tube when the tube is turned ON: 0 - signal present, 1 - signal is missing. 

Second digit shows the state of the High Voltage return: 0 means that the tube returns the same voltage as the one requested (Set) by the controller, 1 - returned voltage is lower than requested, 2 - return voltage is higher than requested. 

The third (right) digit has the same functionality as the second digit but reflects the return of the Emission Current.

Tube Return voltages are monitored within a specific preset tolerance. Emission current is only checked for Set current >5uA - at very low currents, below 5uA the tube return for Emission Current might fluctuate more than the established tolerance and could generate an error otherwise.