mirror of
git://projects.qi-hardware.com/antorcha.git
synced 2024-11-22 08:59:22 +02:00
67 lines
1.9 KiB
Plaintext
67 lines
1.9 KiB
Plaintext
Antorcha vs. Tornado feature comparison
|
|
---------------------------------------
|
|
|
|
Number of LEDs 32 64
|
|
Pixels 16 64
|
|
LED pitch 8 mm 5 mm
|
|
1 arc sec / pixel (1) 28 m 17 m
|
|
1 arc sec / text (2) 70 m 90 m
|
|
LED line length 25 cm 32 cm
|
|
Total stick length 63 cm 53 cm (TBD)
|
|
Outer radius ~ 90 cm ~ 80 cm (3)
|
|
Visible width ~ 100 cm ~ 110 cm (3)
|
|
Sweeps per second ~ 4, bidirectional ~ 3, unidirectional
|
|
Sweep speed (avg.) ~ 8 m/s ~ 15 m/s (3)
|
|
|
|
(1) http://en.wikipedia.org/wiki/Visual_acuity
|
|
(2) 2 text lines, 1/12 display height
|
|
(3) for chain length = 30 cm
|
|
|
|
|
|
Weight
|
|
------
|
|
|
|
Al stick: 52.5 g / 52.7 cm = ~ 1 g/cm
|
|
Chain: 44 g / 19 links = ~ 2.3 g/link
|
|
305 mm / 21 links = 14.5 mm/link
|
|
1.6 g/cm
|
|
Attachment (screw, washers, nut): 2.3 g
|
|
End cap: 1.54 g
|
|
Cable: 1.74 g / 382 mm
|
|
group of 3: ~ 0.14 g/cm
|
|
LED PCB: 4.1 g
|
|
CPU PCB: 4.5 g
|
|
|
|
Not included in the weight calculation:
|
|
- glue
|
|
- adhesive tapes
|
|
- isolation tapes
|
|
- cable binders (if any)
|
|
- heat-shrink tubing
|
|
- cables/wires for inter-board connections
|
|
|
|
|
|
Update rate
|
|
-----------
|
|
|
|
For square pixels we need one update every 5 mm. With the edge moving
|
|
at 15 m/s, that's one update every 1/3000 s. If we assume that,
|
|
including overhead, each 64 bit shift and latch takes about 100 clock
|
|
cycles, the serial bus needs to run at no less than 300 kHz.
|
|
|
|
sclk-1123.png shows the ~250 ns clock pulse generated by the current
|
|
test firmware. CH2 (blue) is signal entering the first LED module,
|
|
CH1 (yellow) is the signal exiting the last module. The absence of
|
|
degradation in a 250 ns pulse suggests that we can go as fast as the
|
|
MCU is able to.
|
|
|
|
|
|
Image size
|
|
----------
|
|
|
|
With a radius of 80 cm the circumference is roughly 5000 mm.
|
|
In order to obtain square pixels at the outer radius, we therefore
|
|
need 1000 lines per rotation, irrespective of speed. Each line
|
|
consists of 64 pixels or 8 bytes of data. Therefore, the full disc
|
|
needs roughly 8 kB of data while a quarter disc needs 2 kB.
|