Six timing positions suited to different skin types
Timing affected by sunlight intensity
Circuit diagram:
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.
