Electronic Sundial / Cadran Solaire électronique (15 minutes)
Électronique / Electronic
|4 to 16 line Decoder / Demultiplexer||4 to 16 Decoder/Demultiplexer with Timer_LED|
|5 to 32 line Decoder 74HC138||5 to 32 line Decoder 74HC154|
|8 to 3 Line encoder||16 to 4 Line encoder|
|32 to 5 Line encoder|
You connect the batteries of each sun dial in
For Hour precision
Sundial need 16 LDRs circuit
For 30 minutes precision
Sundial need 31 LDRs circuit
For 15 minutes precision
Sundial need 61 LDRs circuit
You can replace the 50K potentiometer with a fixed resistor of the appropriate value.
Place LDR and LED at the top of the lines you want.
Aligning the Dial
To use the dial, you need to place it on a level spot (e.g., a sunlit table) and align the "N" arrow with geographic or true north (in the northern hemisphere, the gnomon will also point north; in the southern hemisphere, it will point south). Unfortunately, geographic or true north is not the same as the magnetic north shown by a magnetic compass.
The simplest way to align is simply to look at a watch and turn the dial until the shadow shows the correct time. (Also, make sure you make a daylight savings adjustment if the dial is not printed for the current season's time.) There are other methods. You can use a magnetic compass and correct for magnetic declination.
Reading the Sundial
You read the sundial by looking where the edge of the shadow is, or more precisely where the edge of the shadow further from the gnomon. Except near solar noon (which may be more like 1 pm in the summer if you have daylight savings), that shadow line should be a straight line from the center of the dial out. Near solar noon, because of the wider base of the gnomon, there will be a bend in the shadow line--use the outermost portion of the shadow line.