Sunday, July 7, 2024

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 just fine.
The faceplate text is currently done "quick-n-dirty" 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 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. 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, etc. 
I used this window to feed thru the power cable and temperature sensor cable but I might drill and mount a proper power connector at some point
The keylock is part of the X-Ray safety protocol and prevents 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 remove the key to prevent any accidents. In addition, the XRF enclosure door interlock switch is in-series with the keylock so key must be turned AND door closed for the beam to engage.

The yellow MODE Button serves multiple functions depending on the context.
Single-press is RESET (for Timers, errors, time logging and acts as an Emergency Stop when X-Ray beam is ON).
 Long-press changes operating modes and a double-click switches between memory presets. 
It also acts as a "SHIFT" button while operating parameters are dialed with the rotary encoder (Timer and High Voltage).
The yellow LED is a "READY" indicator showing that the x-ray beam can be engaged at this moment - it turns off if the current conditions disable the x-ray tube - during parameter entry, filament cooling 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. 
Tube and Controller Parameters are then dialed in with the rotary encoder at the position of the 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 Timer mode 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 "Filament Ready" signal returned by the tube: 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 is the same as the second but reflects the return of the Emission Current.

Tube Return voltages are monitored within a specific tolerance. Emission current is checked only 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 will generate an error otherwise.

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