Lighthouse Controller
Kit Construction
revised 12-19-06

NOTE: The photos with the green circuit board have been updated for this new revision.  The main difference between the two boards is that the TIP101 power transistor can be inserted into a set of 3 holes that does not require bending its leads.

(Click here to view the article on the lighthouse)

The first step in constructing the lighthouse controller kit uses the parts in this photo.  The parts include:

  1. Place and solder the IC socket.  Note that the notch in the socket is at the top

  2. Insert and solder the 2 pin header in the pins labeled "dc power"

  3. Insert and solder the filter capacitor - note that the "+" on the board must match up with the "+" on the capacitor.

  4. Insert and solder the 3 pin 7805 voltage regulator.  Note that its flat face goes to the left, as in the photo.

  5. Insert and solder the 470 ohm (yellow/violet/brown) resistor

  6. Insert and solder the red LED.  Its longer lead goes into the "+" hole.

 

This close-up may help with parts placement.  Note that the labeled side of the capacitor is not visible, as it faces the 78L05.

After soldering clip all leads off close to the board as in this photo.  Check for solder bridges and bad joints.

Once you are SURE everything is in order plug the power supply onto the "dc power" pins.  MAKE SURE YOU OBSERVE PROPER POLARITY or you will destroy the voltage regulator.  The red (positive) wire MUST go to the post marked "+".

The LED should light brightly.  If it does not DISCONNECT IMMEDIATELY and check for bad solder joints, reversed components or solder bridges.

Once the LED lights properly proceed with the next step.  Note that this step can be skipped if you don't plan on programming the Picaxe.

Insert the 3 pin header, 22K resistor (red/red/orange) and 10K resistor (brown/black/orange) as in the photo.  Solder and clip leads.

 

Close-up

The parts for the last step are below.

Insert and solder the 1K resistor (brown/black/brown) and TIP101 - be sure to place the TIP101 as shown.  It goes into the 2nd set of three holes that are marked "b c e".  The three holes in front ("e b c" are not used.  The 1000 ohm resistor goes just behind the TIP101

Insert the Picaxe chip into its socket.  Make sure the label is as shown.  You will also note a small indentation on the left side of the chip.  This denotes the end with pin 1 and must be to the left as shown above.  Be careful to insert the pins directly into the socket.  You may need to bend them in a bit to get them to fit properly.  If you are not sure if they went in properly gently pry the chip out with a small screwdriver and try again.

Plug the halogen bulb into the header near the TIP101 and plug the power supply back in.  You should be rewarded with a flashing lighthouse!

 

If you are using one or more LEDs with the unit the construction is the same as for the Halogen bulb.  The LED must have an appropriate current limiting resistor wired in series with one of its leads.  I routinely cut the positive (longer) lead and insert the resistor there.  Here the cable that connects to the board has been soldered to the LED's negative lead (white wire) and the positive lead (red wire) - note the current limiting resistor.  In this example the resistor is 200 ohms.

Here you can see the plug where the LED is connected.  It is the same one that is used for the Halogen but you must observe proper polarity with the LED's positive lead connecting to the pin just above the "b" in "bulb" as show.

Just a reminder that the power plug MUST be plugged in with the RED wire next to the + symbol.  Inserting it backwards for even an instant is sure to destroy the voltage regulator.  Double check before applying power to the unit.   NOTE:  There is a minor modification below that protect against this problem.

PICAXE Software (from article)

symbol some = 110            'delay constant
start:
pwmout 2,0,0                 'turn pin 2 completely off 
b2=1                         'set variable b2 to = 1 
for b1=200 to 0 step -b2     'start a loop to increase brightness

b2=b2+3                      'increase b2 by 3
pause some                   'pause
pwmout 2,b1,b2               'set brightness of LED based on current variables
next b1                      'complete loop
b2=1
pwmout 2, 255,1022:pause 140 'briefly flash full brightness

for b1=1 to 200 step b2      'loop to dim LEDs

b2=b2+3
pwmout 2,b1,b2
pause some
next b1
pwmout 2,0,0
pause 2000                   'pause 2 seconds and...

goto start:                  ' ... do it again

 

Diode Protection Modification

In order to protect the board from incorrectly applied polarity a minor modification can be made. 

First cut the trace that goes between the positive DC Power connection and the voltage regulator.  The trace to cut can be seen clearly in the pghoto below at the very end of the screwdriver tip.  This trace was cut with a small Dremel drill bit.  You can also use a utility knife.  Once it has been cut apply power and confirm that the board is not working by observing the power LED - it should NOT light.

Next solder the small diode on the bottom of the board as shown below.  Note that the banded end of the diode MUST go towards the voltage regulator.

 

Carefully trim the diode's leads and check to make sure there are no shorts or solder bridges.

 Test by applying power.  The power LED should work when the power is applied correctly.  It should not light but no harm will be done if it is BRIEFLY connected backwards.