Six timing positions suited to different skin types, Timing affected by sunlight intensity
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:
A Simple 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.
Source : www.redcircuits.com
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