After a month or so of testing, I considered the LuciLed (Neopixel-based condenser substitute) sufficiently useful to spend the time creating a graphic interface using a Nextion 2.8 (NX3224T028) inch display. Programming Nextions takes a bit of getting used to… to say the very least (!). I had an old Nextion display in my Arduino Uno-based weather station which through the purchase of a commercial one, had been rendered obsolete. So, I cannibalized the old weather station and utilized its Arduino Uno and display. The effort I have put in should not be taken to suggest that a NeoPixel-based ‘condenser’ can replace a nice ‘glass’ one. A ‘glass condenser’ with an appropriate filter will produce darker backgrounds in dark-field, will produce much brighter illumination and has other advantages. However, the LuciLed’s versatility could be useful. You can for example, pretty much instantaneously switch from say oblique illumination from one side to another or from that to Rheinberg or circular oblique in any colour you could wish. There is also the opportunity to animate things such that the system automatically switches from one form, colour and direction of illumination to another. I have yet to implement such animation but it would be simple to do so.
Because it is a serial device, the wiring of the Nextion display, is very straight-forward. I used an Arduino shield to make the wiring a bit easier. Effectively there are just half-a-dozen connections to make; pins 0 and 1 (TX/RX) for serial comms to the Nextion, pin 6 as the Neopixel data line, then there is *independent* 5V power for the Neopixels the supply to which must share a ground with the supply for the Arduino. I use a lab-pack power supply for the NeoPixels because many ‘wall-wart’ supplies use buck-converters that will cause banding when taking pictures. I have incorporated a ~300uF capacitor across the supply lines to the NeoPixels and a 300R resistor in the data line near to the LEDs. Explanations for those components can be found on the web though I would add that everything works fine without them… but better safe than sorry?
There is not a lot that I could write that could not be better illustrated by some pictures and videos. I will place my C++ code on Github. Note that in the second video, I have made no attempt to refocus something that is necessary with achromatic lenses that limit but do not entirely overcome, chromatic abberation, nor have I made the necessary changes to the shutter speed or ISO. Thus, the background in the dark field examples are brighter than they appear through the microscope’s eyepieces and things are sometimes a little fuzzy. A better video when i have the time!
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