![]() ![]() These strips come with sticky backing, so it was a simple peel and stick process. The led strips were fixed to the polycarb strip that goes inside the tube. I went a such a tight squeeze so that I could keep the tube as small as possible = as light as possible. It is also readily available from mail order services that cut to size and spec. Polycarbonate is good material to use in that it is strong, can take a knock or two, does not react badly to strong glues, can be drilled and cut without shattering or splintering, and is reasonably lightweight. The internal diameter (22mm) is such that the Teensy 3.1 and the 14500 (AA size) 3.7v lipo battery can fit inside together. The Polycarbonate tube and strip were ordered with the Teensy in mind. This does not make much difference in general, but was a factor in me deciding to cut the strips at this point rather than have the solder point somewhere in the middle of the poi. This may important for you, as where they are soldered together the gap between the pixels is ever so slightly greater than the rest of the pixels. The leds come on a reel with joins in the continuous strip every 50cm. Adafruit are more expensive and sell them under the ‘dotstar’ name, I don’t know why. The APA102 were ordered from China as they were so very much cheaper than buying them from a US or European supplier. Previous experiments with led strips such as the ws281* did not perform well, gave a speckled image at best, and forced a very slow rotation speed to be used to get effect at all. The APA102 leds were chosen as they are the first affordable pixels to come on a high density strip, that also have a suitably high refresh rate. Total cost for these is less than £200 for the pair. You will have to consider these issues when building your own version.ĪPA102 pixel strips (4圆0leds 144leds/m) The trade off is that the battery will only last roughly half an hour when using images with lots of white in them. Therefore, I am not using a 5v level shifter for these leds, but you can easily fit one (I am saving the remaining space for a flash memory add-on). I decided to go for lightweight, short, fast spin potential, simple, all relating to space inside the tube housing. When designing pixel poi you need to consider: image pixel density, weight of final poi/baton, battery longevity, routine code size, length of baton / poi, brightness of leds. The finished pov / pixel / graphic poi are 185g each, and 51cm long.īefore going further, it is important to note that my requirements for pov poi may well be very different to yours. The simple image utility for the APA102 24bit image arrays to use them in graphic poi / pixel poi can be found here:ĮDIT: weather has improved the browser based image converter utility: "If you'd like to use (or modify) my brother's enhanced version of Mortonkopf's image conversion utility, it is available here. ![]() A red light glows gentle through the plastic indicating charging. The poi are rechargeable via the single Teensy micro usb port, so no opening up to change batteries. The attached code is written to accept any strip length, and uses the FastLED library. ![]() The images are displayed by loading pixel data held in arrays stored in flash memory, and patterns are made mathematically / through code routines. Here is a build example for using apa102 led strips with a Teensy 3.1 as an example of making some relatively cheap pixel poi that are capable of displaying images or patterns. ![]()
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