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.
Circuit diagram:
Tan Timer Circuit Diagram
Parts:
R1 = 47K - 1/4W Resistor
R2 = 1M - 1/4W Resistor
R3 = 120K - 1/4W Resistors
R4 = Photo resistor (any type)
R5 = 120K - 1/4W Resistors
C1 = 10µF - 25V Electrolytic Capacitors
C2 = 220nF - 63V Polyester Capacitor
C3 = 10µF - 25V Electrolytic Capacitors
D1 = 1N4148 - 75V 150mA Diodes
D2 = 1N4148 - 75V 150mA Diodes
Q1 = BC337 - 45V 800mA NPN Transistor
B1 = 3V Battery (two 1.5V AA or AAA cells in series)
IC1 = 4060 - 14 stage ripple counter and oscillator IC
IC2 = 4017 - Decade counter with 10 decoded outputs IC
SW1 = 2 poles 6 ways Rotary Switch (see notes)
SW2 = SPST Slider Switch
BZ1 = Piezo sounder (incorporating 3KHz oscillator)
| 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.
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