Root/tornado/doc/README

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

Archive Download this file

Branches:
master
tornado-v1



interactive