Circuit and Software
d. bodnar revised 10-24-2015
This video shows the lighthouse circuit over an hour or so as the sun sets - the video has been shortened to about 1 minute.
The lighthouse circuit and software have been updated to utilize very bright, very low power LED lamp modules.
These devices contain 24 individual LEDs arranged in an array that sends light out in every direction. They are very bright while only drawing a small fraction of the power that halogen bulbs consume.
In order to make these modules work in a realistic way the software has been rewritten and a faster microcontroller has been used.
The difference in color between the bright white LED module and the warm white module is shown in this video. The warm white is on the left and the bright white is on the right.
The behavior of the lighthouse beacon can be
changed in a number of ways. In its simplest configuration the
light flashes at a rate determined by the rate pot as soon as power
is applied and continues to flash until power is removed. The
CDs light sensor can be used to turn the lighthouse beacon's LED
module on only after dark. When the sun comes up the module
remains off. A jumper can be installed to have the unit
automatically turn off approximately six hours after sunset.
The lighthouse comes back on for six hours after the sun goes down.
Turn clockwise to increase the time between
flashes (maximum about 1 minute)
Auto Off Jumper: if on the lighthouse shuts off after 6 hours of darkness - remove to disable auto-shutoff
Leave the jumper pins open (as shown above) to disable the 6 hour time off after sundown.
Place a jumper on the pins to enable the 6 hour time off (note: CDs must be installed - see next section)
Note: the time that the unit remains on can vary from 6 to nearly 8 hours depending on how often the lighthouse beam flashes. More flashes = longer on time., less frequent flashes = shorter on time.
Dim Jumper: if on the lighthouse lights dimly between flashes - if removed the bulb goes dark between flashes.
The dim jumper keeps the bulb lighted dimly between flashes if not jumpered and completely off in between flashes if jumpered.
Install the CDs light sensor to activate "on when dark, off when light." When shipped the CDs sensor will be installed at the end of a wire extension allowing it to be mounted outside of the lighthouse.
These lights can be installed either way but standard LEDs must have the anode connected to the "+" terminal and the cathode to the other terminal. With standard LEDs you will need a current limiting resistor. That can be installed in the two holes labeled "rLED". You will also have to cut the trace between these two holes on the back of the board.
An Laser Cut acrylic box is also available
Construction from a kit of parts
Red/Black power cable (connect to source of 12 volts DC)
filter capacitor (note pin marked as positive)
7805 voltage regulator
3 @ 10K resistor (brown/black/orange)
1K resistor (brown/black/red)
TIP101 Darlington transistor or IRL 520 Mosfet
10K to 100K potentiometer
8 pin IC socket (note notch at one end)
12F683 PIC processor
white LED Bulb
2@ connecting wires (for CDs cell and LED unit)
3@ 2 PIN headers
Install the first set of components as shown here. Note that the 7805 voltage regulator and capacitor both need to be inserted in the proper orientation. The notch on the 8 pin socket should be pointing towards ICSP label as shown. The red wire from the power cable goes to the hole labeled with a plus (+) sign.
Here is another view of the board and its first set of components.
Connect the power leads to a 12 volt DC power source and check the voltage at pins 1 and 8 on the IC socket (circled in yellow). It should measure 5 volts plus or minus 0.1 volt.
Here is a view of the back of the board. You will notice that a good number of holes are not used.
Add the remaining components. The power transistor (IRL 520) must be in the set of holes closest to the IC socket and must be oriented as shown.
The light sensor plugs into one end of a twisted red/black wire that is soldered to the CdS labeled holes. Make sure the leads do not touch. You may want to trim the leads to a 0.5 inch length to keep them apart.
The 24 LED module plugs into the other twisted red/black wire. The pins on the LED module need to be bent in a bit to fit the socket. It can be inserted into the socket either way.
The 12F683 processor must be installed with the notch (sometimes a small dot) pointing towards the ICSP label.