Tan Timer

Six timing positions suited to different skin types

Timing affected by sunlight intensity

Circuit diagram:

Tan Timer


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-typeFeaturesExposure time
I & childrenLight-eyed, red-haired, light complexion, freckly20 to 33 minutes
IILight-eyed, fair-haired, light complexion28 to 47 minutes
IIILight or brown-eyed, fair or brown-haired, light or slightly dark complexion40 to 67 minutes
IVDark-eyed, brown-haired, dark complexion52 to 87 minutes
VDark-eyed, dark-haired, olive complexion88 to 147 minutes
VIThe darkest of all136 to 227 minutes
Note that pregnant women belong to Photo-type I