Hello everyone,
I posted on this forum several months ago and received some good help from @kgray9. Originally, the scope of my project was controlling an EL panel but that has since expanded. I have done quite a bit of research into how others have tried to solve this problem and there seems to be various approaches, which I will outline later. Please understand that my knowledge of electronics is such that I know enough to realize I really know nothing. So please do not assume I understand.
Goal:
The device being created a telescope "flat panel" with motorized cover. The panel is placed over the telescope and evenly illuminates the optical path, which allows for calibration frames to be taken. This is controlled via the ASCOM protocol which allows for the benefits of adjustable brightness instead of adjustable exposure time. The biggest thing to consider is that the panel seems to need a refresh rate faster than 30kHz for certain cameras. Other implementations seem to be slower and still works fine, so some testing to confirm this will be needed.
I need to control an EL panel and servo via an arduino* that can connect to a piece of software we use in the industry. The software side of things is mostly covered it seems. The hardware is the main issue.
*other boards are fine too
What I found:
When it comes to controlling EL panels, it seems to be most common to use a transistor or FET to modulate the 12v supply to a PWM capable inverter. These types of inverters seem to be uncommon with the most available one being the EOE276 from Ellumiglow. This takes 12v DC and steps up to 130v AC. One tricky part here is the max freq, but more on this later. Using a logic level N type transistor should fit the bill here, with numerous options to choose from.
You can also go slightly more complicated (or maybe correct?). There are several schematics online that I have found, with the following two "best" being the best I found:
This layout from David Allmon seems to be quite compact. There is a supply issue with the IC switch and the transistor, but I am assuming alternatives will work. One annoying thing is that the 100uF cap has be changed if using larger EL Panels. I'd prefer to not have to do that.
He did use a novel approach to get a 16bit style dimming in the code, which I like. Adding servo control to this should be pretty simple as well.
This one from RunTJoe is lot more complicated and I do not fully understand why he chose this path. One thing I know I would want to eliminate is the DC/DC converter as having to adjust the pot to 5v each time one is made would get old fast. A simple step down circuit should work here, right? Or even a LM317? A voltage divider could also be useful as the waste heat could help ensure the circuit stays above the dew point during an imaging session.
The main thing I do not understand is the DAC, OpAmp, Darlington set up as those go above my head. It seems that he is stepping up the 3.3v to ~10v for the inverter. This seems like a roundabout way if you already have a 12v supply on the PCB. But maybe there are benefits to this design.
:
Next Steps:
The problem I want to avoid is creating a dependency on the the supply of these inverters. And given that I have already had one randomly die on me after barely even a single use, I am not very confident in their longevity, especially in the harsh climate of being exposed overnight to freezing temps. The listed inverter also seems to have a 1000hz limit in the manual (though the website says otherwise)
This is where I began to wonder if the inverter could be eliminated completely and instead, be integrated into the design. Having taken my busted one apart, they seem pretty simple with the main part being what I presume to be a transformer to step up the voltage. Nobody has done this part so I am mainly in the dark here.
It seems I need help to:
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Decide if integrated or separate inverter is smarter.
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Confirm board and PCB layout for servo and EL Panel (depending on layout)
These designs used the Nano, but I have also seen one that used a SEEED XIAO which I am not familiar with but I like the size!
So, what do yall think? What would you change about these designs?
Thanks in advance.