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LED Top with Special Effects

Spin the top to display programmed text

LED Top with Special Effects
If you fit a line of LEDs on a circular PCB and power them on continuously, they generate rings of light when the board is spun. If you add a microcontroller, you can use the same set of LEDs to obtain a more interesting effect by generating a ‘virtual’ text display. This article also describes a simple technique for using the Earth’s magnetic field to generate a synchronisation pulse. The potential applications extend from rotation counters to an electronic compass.
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All SMD 0805, 1 %, unless otherwise indicated
R1,R6,R7 = 100k
R2 = 150Ohm
R3,R9 = 47k
R4 = 4kO7
R5 = 1M
R8 = 10k
R10 = 22k
R11,R12 = 330Ohm 9-pin SIL resistor array

C1,C5,C7 = 100nF (SMD 0805)
C2,C9,C10 = 47µF 16V (SMD electrolytic)
C3 = 680nF (SMD 0805)
C4 = 2µF2 16V (SMD 0805)
C6 = 10nF (SMD 0805)
C8 = 47pF (SMD 0805, NP0)

L1,L2 = 150mH fixed inductor, Qmin = 50, RM5 (12x16 mm), e.g. Fastron 11P-154J-50 (Reichelt.de # L-11P 150M)

D1-D8 = LED, red, 628nm, SMD 1206 with lens, e.g. Kingbright KPTD-3216SURC (Reichelt.de # 1206K RT)
D9-D16 = LED, yellow, 588 nm, SMD 1206 with lens, e.g.. Kingbright KPTD-3216SYC (Reichelt.de # 1206K GE)
D17 = zener diode 5.1V 1.3 W (BZV85-C5V1)
IC1 = LM358 (SMD SO8)
IC2 = ATmega8-16AU (Atmel), SMD TQFP-32

S1 = DIP switch 2-way (MULTICOMP MCDS02, DIL04)
K1, K2 = CR2032 SMD battery holder (Renata SMTU-2032-1-LF, SMTU-2032-1, Reichelt.de # KZH 20PCB-1)
K3 = 6-way DIL pinheader, lead pitch 2.54mm (Tyco-AMP # 1241050-3 AMP)
Polyamide screw, M6x20 with nut and 2 washers
BAT1, BAT2 = Lithium button cell type CR2032
Kit of parts incl. SMD-populated board, Elektor SHOP # 071120-71
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