In our neighborhood, the security patrol vehicles are all fitted with white window-mounted strobe lights. These units are readily available at a very low cost (between ZAR120.00 - ZAR200.00).
- Brand new and high quality.
- Easy to install.
- With 4 suction cups for quick screen mount.
- Adjustable angle.
- Bright white, long lasting.
- LED Quantity: 8
- 3 - 6 flashing modes.
- Color: white
- Voltage: DC 12V
- Size: about 20*10*5 cm
- Powered via car cigarette lighter
These lights does have some drawbacks:
- The LEDs fitted in the unit, are normal super-bright 5mm LEDs, with a typical light intensity of 13Lm. Ideal for night time patrol, but not clearly visible during the daytime.
- Total wattage of all 8 LEDs is only 0.64 Watt.
- Depending on the software version, the unit can have up to 6 different flashing modes. In all tested units, the most visible flashing sequence is mode 3 or mode 5. Unfortunately, the selected flashing mode is not saved. Therefore, each time the unit is switched on, the user must press the MODE button several times to select the correct flashing sequence. With one unit fitted in the rear window, and another fitted to the front windscreen, this can become irritating each time the lights are used.
- The flashing mode is not visible from inside the vehicle during the day, and the user must stand outside the vehicle to verify the flashing sequence.
- There is no visible indication during the day for the user to know if the lights are switched on or off.
In this Instructable, I will show you how to convert the unit into a more practical unit, by doing the following modifications:
- Replace the 5mm LEDs with eight 1 Watt high-power LEDs
- Increase the light intensity to around 110Lm per LED
- Increase total wattage of all 8 LEDs to 8 Watt.
- Replace the MODE button with a POWER ON indication LED
- Changing the microcontroller and software to have the unit switch on in the correct flashing mode.
Step 1: Buying the LEDs
All LED components can be purchased on Bid or Buy. The best service, with the lowest shipping rates, is LED Select. Delivery is via door-to-door courier, and delivery is normally within 3 days of placing the order.
2 x 12V, 4 - 7 1 Watt LED Driver
Step 2: Buying the Rest of the Components
The rest of the components can be purchased on line. Locally, Rabtron can supply all the components, except the high power LEDs, as required. They also offer on line shopping.
1 x 5mm LED Holder
1 x 0.1uf Capacitor
1 x 1N4007 Diode
1 x 8-pin IC Socket
1 x Veroboard
Step 3: Disassembling the Unit
Disassembly of the unit is simple and quick.
- Remove the two screws on the side of the unit to separate the light unit from the mounting base.
- Remove the end cap from the unit on the side where the power cable enter by undoing 3 - 4 screws.
- Gently pull out the PC Board to expose the two sets of wires on the PC Board (power and MODE button).
- Desolder both set of wires. Make sure to mark the positive and negative power connections.
- With both set of wires disconnected, remove the PC Board completely from the aluminium housing.
Step 4: Replace MODE Button With LED
The MODE button is no longer needed, and is replaced with a 5mm Diffused Green LED. This LED will be visible during the daytime, and will not be a distraction during the night.
! ! DO NOT USE A BRIGHT LED ! !
- Remove the MODE button from the housing
- Disconnect the wires from the button
- Cut the LED leads just long enough to solder on the wires, but long enough to allow for a 90 degree bend
- Add heat shrink to the wires
- Solder the wires to the LED
- Cover the exposed leads with the heat shrink
- On the PC Board side of the wires, solder the 470R resistor to the negative wire
- Cover the resistor with heat shrink
- If required, cut the edges of the 5mm LED holder to fit inside the push button hole
- Fit the LED Holder in the casing
- Insert the LED into the LED holder
Step 5: Preparing the PC Board
Removing the original LEDs:
- Remove the two lenses from the PC Board
- Starting with the LEDs, remove all LEDs
- Next, remove the transistors and capacitor
- Remove the microcontroller. As this is a One Time Programmable (OTP) chip, we will not be using it again.
- Lastly, remove the resistors and diodes.
Step 6: Preparing the 1 Watt LEDs
We now need to assemble the eight 1 Watt LEDs:
- I use Prestik to hold the LED base plates in position
- Apply a small amount of thermal heat sink paste to the center of the base plate
- Ensure correct polarity of the LED
- Solder LED to base plate
Step 7: Mount the New LEDs to the PC Board
Mounting the new LEDs to the PC Board:
- Only do four LEDs at a time
- Apply a small amount of thermal heat sink plaster where the first four original LEDs were mounted
- Place the assembled the first four LEDs on the plaster in alternating polarities
- After the LEDs are mounted, cover them with the lens, ensuring the LEDs are all in the center of the lens.
- Apply a small amount of thermal heat sink plaster for the rest of the LEDs
- Place the last four LEDs on the plaster in alternating polarities
- After the last LEDs are mounted, cover them with the lens, ensuring the LEDs are all in the center of the lens.
- Wait for the plaster to dry
The plaster can take up to 24 hours to dry completely
Step 8: Preparing the LED Drivers
The high power LEDs requires a LED Driver for each set of four LEDs. Prepare the two drivers as follow:
- Remove the the stainless steel pins from each driver PC Board
- Add power leads to the drivers (orange is positive, purple switching negative)
- The unit is not polarity sensitive, wires can be mounted on any of the connections
- Bend the power leads and route them back to the LED leads
- Insert the drivers into a piece of heat shrink as shown
- Heat up the heat shrink and ensure the driver is fully covered
Step 9: Building the New Controller
As we have removed all the original components from the unit, a new controller must be build. I opted to use a piece of veroboard to build the circuit on. Make sure the new board will be narrow enough to fit inside the aluminium housing.
Solder components as indicated:
- Start with the resistors and diode first
- Cut the tracks underneath the resistors and diode
- Add the 0.1uf capacitor
- Add the IC socket. An IC socket is added to the board to be able to remove the IC later if required
- Cut the tracks between the IC pins
- Add the 78L05
- Add the two transistors
- Add the 100uf, 25V capacito to the top of the IC socket
- Add the 100uf, 16V capacitor to the left of the 78L05
- The two jumpers can be made by soldering across the two tracks
- Add the two power wires.
- Do not insert the microcontroller at this stage
- Apply power to the unit, and verify that 5V is present across pin 1 & 8 on the IC socket
Step 10: Programming the Microcontroller
The code was written using Flowcode for PIC. The chip used is the Microchip PIC 12F675. See attached files. The HEX file is included for easy uploading to the microcontroller via the MPLab software. I used MPLab with a PicKit 3 programmer.
- Open MPLab
- Go to File/Import
- Open 1W_Led.hex
- Go to Configure/Select Device
- From the list, select PIC12F675
- Go to Configure/Configuration Bits
- Clear "Configuration Bits set in code" checkbox
- Select INTOSC: I/O Function on GP4
- Disable WDT
- Enable PWRT Timer
- Set MCLR to Internal
- Disable Broun-out detect
- Upload the code to the microcontroller using your programmer
- Get a suitable piece of heat shrink to cover the new controller board, but do not shrink it now
Step 11: Almost Done...
The modification is almost done. If all went well, the work should have taken about 1 - 2 hours.
We have completed the following:
- Changed the MODE push button to POWER ON indication LED
- Prepared the new LED drivers for installation
- Build the new controller board
- Programmed the microcontroller
Al that is left to do, is to wait for the LED heat sink thermal plaster to dry (from Step 7).
Step 12: Complete the New LED Wiring
Once the heat sink thermal plaster has dried, we can continue with the assembly.
- Remove the lens covers
- Insert jumpers between the first group of four LEDs
- Insert jumpers between the last group of LEDs
- Do not connect the left and right group of LEDs together
Step 13: Connect the LED Drivers to the LEDs
We can now begin to reassemble the unit.
- Find a suitable place to drill holes for the LED Driver wiring
- Make sure the holes are drilled in such a way to avoid the wiring to be pinched between lens openings
- Feed the LED Driver output wires through the holes
- Solder driver wires to the LED groups
- Pink wire goes to positive of the LEDs
- White wire goes to negative of LEDs
- Repeat for both drivers
- Test both LED drivers
- Replace LED lens onvers
Step 14: Connecting the LED Drivers
Find a suitable place to mount the LED drivers.
- Connect one wire of the LED driver power to the positive rail on the PC Board
- Place LED driver onto the PC Board, making sure to leave room on both sides of the PC Board to still fit into the enclosure.
- Ensure the led driver does not obstruct the lens cover screws
- Repeat for the second LED driver
- Each driver will now have one unconnected wire
Step 15: Connecting the Controller Board
It is now time to connect the controller board.
- Find a suitable place to mount the controller between the two LED drivers
- Solder the positive wire (+) to the positive rail on the PC Board
- Solder the negative wire (-) to the negative rail on the PC Board
- Solder the LED driver closest to the controller power wiring to the controller board to the point marked with an arrow close to resistor R1
- Lastly, solder the 2nd LED driver to the second arrow close to resistor R2. Ensure that this wire is kept long enough to ensure you can still cover the controller board with heat shrink
- Power up the unit with a power supply, and ensure everything is working correctly
- Cover the controller board with heat shrink, making sure that the board is completely covered
Step 16: PC Board Assembly
The modification is now complete, and all that is left is to secure the LED drivers and controller board to the PC Board.
- Using a glue gun, glue the two LED drivers to the ends of the PC Board, making sure to leave room on both sides of the PC Board to still fit into the enclosure.
- Ensure the led driver does not obstruct the lens cover screws
- Next, glue the controller board to the PC Board
- Ensure the controller board does not obstruct the lens cover screws
- Make sure there are no wires that can move around. If necessary, use some glue to secure them
Step 17: Securing Power LED
Before assembly can begin, secure the LED.
- Bend the LED pins 90 degrees, as close as possible to the led holder
- Wires from the LED should face towards the inner part of the casing
- Using the glue gun, secure the LED with a generous amount of glue
- Ensure the LED is glued and as low as possible
Step 18: Reassemble the Unit
With everything connected and secured, reassembly can begin.
- Slide the PC Board about 3/4 back into the casing, taking care to clear the LED
- Solder the LED positive wire to the positive rail on the PC Board
- Solder the LED negative wire to the negative rail on the PC Board
- Solder the power supply cable back in its original position
- Finally, slide the PC Board completely in position
- Bench test the unit for the last time before closing up
- Route the power cable through the exit hole
- Replace the end cap
- Secure the light module onto the mounting base