This project is for a module that can pulse a light to simulate a lighthouse. The module has a variable resistor to adjust the timing to suit your need. It also has an open-collector transistor output to allow the use of a high power LED or lamp. The maximum recommended current for the light source is 500mA. A standard 5mm white LED can also be used.
For this project I created a general purpose circuit and PCB that could also be used for other projects. Therefore it has components on the PCB that are optional.

IC1 is an eight pin microcontroller which will be programmed to flash the light. For this project I will use a microcontroller with Pulse Width Modulation (PWM) to vary the light intensity and an analog input for a variable resistor to manually adjust timing.
Transistor Q1 is used as an open collector switch controlled via output GP2 and resistor R6.
The GP0, GP1 and GP5 outputs are not used so the resistors R2, R3 and R4 are not required.
Power is supplied to the circuit via the 5v regulator IC2 and related capacitors C1, C2 and C3. The diode D1 protects the circuit from reverse polarity connections.

The PCB measures 27mm by 30mm and has two 2.8mm diameter mounting holes. All the connections are on one side and connections can be made by soldering wires directly to the PCB or by using a pin header connector.

I always start by assembling the smallest components and those less affected by heat first. So I solder the resistors first followed by the diode making sure to orientate the diode correctly. If using an edge connector I would solder that next followed by the socket for the microcontroller. Then solder in the capacitors C1 and C2 followed by the variable resistor.
Next solder in the transistor and voltage regulator. Finally solder in the capacitor C3 as this is the tallest component but make sure it is aligned correctly matching the PCB and the capacitor.
Check all the joints for dry joints and there are no solder splashes.
Do not plug in the microcontroller until the test phase below.

I have quoted Rapid Electronics Order codes above for reference. Not all components are available (12F615) at present and some components may be out of stock. Please note, some items have a minimum order quantity. You can find some items online at a better price.

The PCB and a pre-programmed PIC Microcontroller can be purchased from me on request. Please use the contact form to contact me.

I use Mikroe C compiler to develop the program for the PIC Microcontroller. This compiler sets the microcontroller fuses by selecting the options in the project settings user interface. This makes it easy to select the correct options as only the options relevant to the microcontroller you are using are displayed. This compiler is free to use for programs less that 2k in size.
For other compilers you may have to set the fuses in the program itself.
By using the PWM module built in to the microcontroller the program is more simple. You do not have to take care of pulsing the output at the correct duty cycle.

Testing starts with a voltage test before plugging in the Microcontroller. Connect a 9v-16v power supply to the V_in and Gnd pins on the PCB and measure the voltage across pins 1 and 8 of the 8 pin socket. It should read approximately 5v.
Next, if you connect the light between V_in and GP2 you can use a small piece of wire to bridge pins 1 and 5. The light should illuminate. This checks the transistor is switching the light on and off.
If both these tests are ok disconnect the power supply before plugging in the PIC microcontroller. Make sure you handle with care as static electricity on the IC pins can damage it. Also make sure you align pin 1 correctly.
Now you can apply power to check if the LED is pulsing on and off. You can adjust the variable resistor to change the speed of the pulsing one and off and the time in between flashes.
See the FAQ below if you face any issues during testing.

The module produces a realistic pulsing light with a good adjustable range. The cost is quite reasonable and by using a microcontroller we can change the program to alter the desired effect.
For example we can make the following changes: