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.)
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.
|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|
- 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.