Root/
| 1 | Antorcha vs. Tornado feature comparison |
| 2 | --------------------------------------- |
| 3 | |
| 4 | Number of LEDs 32 64 |
| 5 | Pixels 16 64 |
| 6 | LED pitch 8 mm 5 mm |
| 7 | 1 arc sec / pixel (1) 28 m 17 m |
| 8 | 1 arc sec / text (2) 70 m 90 m |
| 9 | LED line length 25 cm 32 cm |
| 10 | Total stick length 63 cm 53 cm (TBD) |
| 11 | Outer radius ~ 90 cm ~ 80 cm (3) |
| 12 | Visible width ~ 100 cm ~ 110 cm (3) |
| 13 | Sweeps per second ~ 4, bidirectional ~ 3, unidirectional |
| 14 | Sweep speed (avg.) ~ 8 m/s ~ 15 m/s (3) |
| 15 | |
| 16 | (1) http://en.wikipedia.org/wiki/Visual_acuity |
| 17 | (2) 2 text lines, 1/12 display height |
| 18 | (3) for chain length = 30 cm |
| 19 | |
| 20 | |
| 21 | Weight |
| 22 | ------ |
| 23 | |
| 24 | Al stick: 52.5 g / 52.7 cm = ~ 1 g/cm |
| 25 | Chain: 44 g / 19 links = ~ 2.3 g/link |
| 26 | 305 mm / 21 links = 14.5 mm/link |
| 27 | 1.6 g/cm |
| 28 | Attachment (screw, washers, nut): 2.3 g |
| 29 | End cap: 1.54 g |
| 30 | Cable: 1.74 g / 382 mm |
| 31 | group of 3: ~ 0.14 g/cm |
| 32 | LED PCB: 4.1 g |
| 33 | CPU PCB: 4.5 g |
| 34 | |
| 35 | Not included in the weight calculation: |
| 36 | - glue |
| 37 | - adhesive tapes |
| 38 | - isolation tapes |
| 39 | - cable binders (if any) |
| 40 | - heat-shrink tubing |
| 41 | - cables/wires for inter-board connections |
| 42 | |
| 43 | |
| 44 | Update rate |
| 45 | ----------- |
| 46 | |
| 47 | For square pixels we need one update every 5 mm. With the edge moving |
| 48 | at 15 m/s, that's one update every 1/3000 s. If we assume that, |
| 49 | including overhead, each 64 bit shift and latch takes about 100 clock |
| 50 | cycles, the serial bus needs to run at no less than 300 kHz. |
| 51 | |
| 52 | sclk-1123.png shows the ~250 ns clock pulse generated by the current |
| 53 | test firmware. CH2 (blue) is signal entering the first LED module, |
| 54 | CH1 (yellow) is the signal exiting the last module. The absence of |
| 55 | degradation in a 250 ns pulse suggests that we can go as fast as the |
| 56 | MCU is able to. |
| 57 | |
| 58 | |
| 59 | Image size |
| 60 | ---------- |
| 61 | |
| 62 | With a radius of 80 cm the circumference is roughly 5000 mm. |
| 63 | In order to obtain square pixels at the outer radius, we therefore |
| 64 | need 1000 lines per rotation, irrespective of speed. Each line |
| 65 | consists of 64 pixels or 8 bytes of data. Therefore, the full disc |
| 66 | needs roughly 8 kB of data while a quarter disc needs 2 kB. |
| 67 |
Branches:
master
tornado-v1
