Tan Meter

Six timing positions suited to different skin types

Timing affected by sunlight intensity

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.

Tweet