Ilse  Joostens
About the article

Laser Time Writer

Revisited!

Laser Time Writer
In this year's January & February issue we presented the Laser Time Writer as a high-tech upgrade for our successful Sand Clock. The LTW writes the time with a violet laser on a piece of ‘glow in the dark’ sticker material. After a while the numbers fade and a new write cycle can start over. Because there is no inevitable noise when the sand bed of the original sand bell is shaken, the LTW is a lot less exciting.
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Products
Extra info / Update
Tags: Arduino, Laser, clock, PIR sensor

Level: Advanced

Time: 1.5 hours approx.

Tools: Solder iron with fine tip, Mechanical tools, PC

Cost: €120 / £105 / $150 (complete kit); €45 / £40 / $55 (upgrade kit)
Component list
Component List
Resistors
All SMD 0805
R1,R2,R3,R11 = 220Ohm
R4 = 1kOhm
R5–R9 = 4.7kOhm
R10 = 100kOhm

Capacitors
C1–C4 = 100nF, SMD 0805 MLCC
C5 = 10μF, 10V, SMD 1206 MLCC
C6 = 22μF, 16V

Semiconductors
D1,D2,D3 = S2J-E3
T1 = BCX56
IC1 = Würth Elektronik type 173 010 578, 5V/1A SIP3 DC/DC converter
IC2 = PCF2129A

Miscellaneous
K1 = set of pinheaders 0.1’’ pitch, straight (1 pc 10-pin, 2 pcs 8-pin, 1 pc 6-pin)
SERVO_Z, SERVO_L, SERVO_R = 3-pin angled pinheader, 0.1’’ pitch
B1 = CR2032 battery holder with CR2032 button cell
Arduino UNO R3 of equivalent
SPST NO pushbutton, 6mm hole
Wire set (red/black) and heatshrink tubing
Laser module, 12x35mm, 405 nm, 5–10mW (eBay)
HC-SR501 PIR movement detector

Mechanical parts
8 x bolt M2x10 Pozidriv/Phillips
4 x bolt M2x6 Pozidriv/Phillips
2 x nylon washer M2
2 x hexagonal spacer 10mm F/F M2
6 x bolt M2.5x8 galvanised steel Pozidrive DIN 7985A
2 x bolt M3x8 galvanised steel Pozidriv DIN 7985A
15 x bolt M3x10 galvanised steel Pozidriv DIN 7985A
2 x bolt M3x12 galvanised steel Pozidriv DIN 7985A
8 x hexagon nut M2 galvanised steel DIN 934
9 x hexagon nut M3 steel DIN 934
3 x lock nut M3 galvanised steel DIN 985
4 x cap nut M3 high, chrome plated, DIN 1587
6 x spacer bush 3mm high polyamide for M3
4 x hexagonal spacer 25mm M/F M3 nickel plated brass (minimum 33mm total height, e.g. TME TFM-M3X25/DR213)
4 x spacer sleeve, 5mm high, plastic, for M3, outer diameter 6mm
1 x brass tube, diameter 4mm x 0.5mm, length 35mm
4 x self-adhesive rubber foot for base plate
4 x self-adhesive rubber foot for acrylic glass support
3 x micro servo tower Pro MG90S or MG90 metal gears
Glow-in-the-dark sticker material, approx. 80 x 150mm (eBay)
Extruded (XT) 3mm Plexiglass (acrylic sheet), clear, laser cut
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