LCD Vacuum Sensor

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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Nicolas Krause
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LCD Vacuum Sensor

Post by Nicolas Krause » Fri Jun 26, 2020 3:34 am

To use my thermocouple vacuum gauge and to continue improving my embedded development skills I've been working on programming a TI Tiva C Launchpad via the MeCrisp Stellaris language to read a value from the vacuum gauge and then print the value to the screen. It's been slow going, as I'm new to Forth (MeCrisp Stellaris is a dialect of it), but tonight I finally was able to get the pins outputting SPI signals so that I can communicate with the LCD. In addition I figured it was better to break this off from my main thread and start this smaller one. I plan on documenting the development of the program, pcb and final product here.
IMG_1095[1].JPG

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Richard Hull
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Re: LCD Vacuum Sensor

Post by Richard Hull » Fri Jun 26, 2020 4:07 am

If I didn't have so many TC gauge meters and readouts with mating gauge tubes laying around the lab, I would make one up using the Arduino Mini-Pro and backlit I2C LCD readout. The TC gauge article in an older Bell Jar gave hard non-linear data points all along the pressure vs. voltage outputs from several different common gauge tubes. With a lookup table and interpolation math in the program such a project is very doable for any micro controller.

The BJ article should be on the BJ website.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Nicolas Krause
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Re: LCD Vacuum Sensor

Post by Nicolas Krause » Sat Jun 27, 2020 8:45 pm

If I were in your position I probably wouldn't be doing this either Richard! But I'm learning a new programming language, I have a design in mind for the PCB that I quite like, and I think this will be a very nice little project. The first goal of this whole Fusor project is to learn, and this is helping me do that in spades. By way of an update today I was able to get the LCD to turn on. I'd initially miswired some pins, and I had to determine the configuration sequence but all is well!
IMG_1096[1].JPG

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Richard Hull
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Re: LCD Vacuum Sensor

Post by Richard Hull » Sun Jun 28, 2020 2:31 am

I have always done a ton of useless projects just so I could learn something new and put it into practice so that from that point on, I would own that possess and knowledge for life.
Doing anything that seems useless to gain and possess knowledge is always a good thing.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Nicolas Krause
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Re: LCD Vacuum Sensor

Post by Nicolas Krause » Sat Jul 04, 2020 2:34 am

Just a quick update here, I've decided to swap out the screen for a simpler text LCD. I was looking at the programming task ahead of me, and it required writing some graphics drivers for the dot matrix LCD. Rather than struggle with that task in a new language, I figured it was better to go for a simpler solution so that I could crack on with other problems. The replacement screen is on its way and I'm currently in the process of configuring the ADC on the board to take a voltage measurement from the circuit. I appreciate you posting all the Bell Jar newsletters here Richard, always good to read, especially the latest issue with its description of a turbopump controller, my next project!

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Richard Hull
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Re: LCD Vacuum Sensor

Post by Richard Hull » Sat Jul 04, 2020 2:48 am

I am with your Nicolas. I have used only the arduino and the massive library group of custom apps assembled over the years at arduino.cc. It is so useful to grab a suitable special function library that 80% of the tough work is already done for me by folks a lot smarter than me. I built a TFT GM counter the TFT screen took me one week to work out well. It was not worth the effort. I have found that a nice library exists to effortlessly use backlit 2X16 and 4X20 LCD displays as well as the I2C organic LED displays (oLED), that reduces the effort to just spilling on the desired text and various computed data results as numeric data. No line of cell counting needed to place the text or data. The arduino is very well suited due to its long history and numerous free libraries. The IDE is easy to use and learn as it is a variant of C.

Folks who like to play fancy custom graphics can have at it with the TFT displays. To my way of thinking if you plan on making 1000 pieces of a custom system, then the time might be well spent. Me, I just want an easy to use and easy to implement readout of plain text and data.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Nicolas Krause
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Re: LCD Vacuum Sensor

Post by Nicolas Krause » Sat Sep 12, 2020 3:33 am

Happy to report, that without too much trouble I can now write text out to my LCD screen. It took a solid 8 weeks for the parts to arrive due to mail delays with the pandemic, and since completing my coop and moving back home I haven't had much spare time to work on it. All the components of my program now work individually, I can read values on the ADC, write out values to my screen. I just have to confirm that my amplifier is working properly, and then I can begin to work on my PCB design.
IMG_1149[1].JPG

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Nicolas Krause
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Re: LCD Vacuum Sensor

Post by Nicolas Krause » Mon Sep 14, 2020 10:06 pm

Happy to report progress continues quickly, I've written a little function that updates to the screen. It converts an int value to a series of char values and prints them out. Forth is a fun little language!
IMG_1154[1].JPG

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Nicolas Krause
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Re: LCD Vacuum Sensor

Post by Nicolas Krause » Mon Oct 12, 2020 6:04 pm

I've got my amplification circuit with a bit of spare time this past Saturday. I'm now looking at designing the PCB for the gauge, I've googled this a bit, but is anyone aware of the type of connector/plug use for vacuum thermocouple gauges? It'd be quite handy just to be able to order one from a supplier like digikey and make my own cable. Failing that I've been monkeying with the idea of designing a discrete PCB that would connect to the device that I could run wires from myself.

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Re: LCD Vacuum Sensor

Post by John Futter » Mon Oct 12, 2020 6:17 pm

Most of the thermocouple gauges use the octal valve (tube) plug on them so you will want the octal valve (tube) socket

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