Tan Timer

Six timing positions suited to different skin types
Timing affected by sunlight intensity

Circuit diagram:

Tan Timer

Parts:

R1	47K 1/4W Resistor
R2	1M 1/4W Resistor
R3,R5	120K 1/4W Resistors
R4	Photo resistor (any type)

C1,C3	10µF 25V Electrolytic Capacitors
C2	220nF 63V Polyester Capacitor

D1,D2	1N4148 75V 150mA Diodes

IC1	4060 14 stage ripple counter and oscillator IC
IC2	4017 Decade counter with 10 decoded outputs IC

Q1	BC337 45V 800mA NPN Transistor

SW1	2 poles 6 ways Rotary Switch (see notes)
SW2	SPST Slider Switch

BZ1	Piezo sounder (incorporating 3KHz oscillator)

B1	3V Battery (two 1.5V AA or AAA cells in series etc.)

Device purpose:

This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight.
A Rotary Switch sets the timer according to six classified Photo-types (see table).
A Photo resistor extends the preset time value according to sunlight brightness (see table).
When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

Photo-type	Features	Exposure time
I & children	Light-eyed, red-haired, light complexion, freckly	20 to 33 minutes
II	Light-eyed, fair-haired, light complexion	28 to 47 minutes
III	Light or brown-eyed, fair or brown-haired, light or slightly dark complexion	40 to 67 minutes
IV	Dark-eyed, brown-haired, dark complexion	52 to 87 minutes
V	Dark-eyed, dark-haired, olive complexion	88 to 147 minutes
VI	The darkest of all	136 to 227 minutes
Note that pregnant women belong to Photo-type I

Notes:

Needing only one time set suitable for your own skin type, the rotary switch can be replaced by hard-wired links.
A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time when the device is off, or the ICs could be damaged.