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Picture of Dual Laser-Guided Parking System
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This is a great way to park  in your garage without the hanging tennis ball.  You know the one your kids use for batting practice, that only lasts one day.  

This system uses a small laser mounted on the ceiling that guides you into the garage and helps you park in the right spot every time.  The lasers are powered by the garage door opener light so it is only on when the garage door opener light is on.

Parts List
2 - Laser Lights (I used two 5mW laser diodes from http://www.dealextreme.com) however you can use any pen laser light
2 - Insulator tubes for laser diodes, not needed if you use laser pen
1 - 2 Outlet Lamp Socket
1 - DC wall transformer (3.5 to 4.5 Volts DC is what most laser lights run on. If you can't find a wall transformer between this voltage you will need to make a voltage divider to get the correct voltage)
2 - Angle L-Brackets (Laser mounts)
2 - Small gauge two conductor wire ~ 6 feet long (Like an old telephone cable)
4 - 2 conductor terminals

 
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Step 1: Identify the power requirements for your lasers

Picture of Identify the power requirements for your lasers
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I bought my lasers from www.dealextreme.com item #13378 for about $1.50.  These lasers run on 3.5 to 4.5 Volts and are 5mW. 

However, if you already have a pen laser light, that would also work out great since you don't have to build the insulated housing.

Step 2: Identify the Power Supply

Picture of Identify the Power Supply
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My power supply was taken from an old cordless phone.  It's output is 7.5 Volt DC  150mW.  You will notice that this voltage is greater than the lasers can accept, so I had to make a voltage divider to get the voltage down from 7.5 to the needed 3.5 to 4.5 volts.

The Wikipedia Definition of a Voltage Divider is "In electronics, a voltage divider (also known as a potential divider) is a simple linear circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin)."

Since I needed that voltage to the laser lights to be less than what the wall transformer produces I needed to make a Voltage Divider.
 
The easiest was to make the voltage divider is to go out on the internet and search for a voltage divider calculator, try to find one that also has current in the calculator - like (http://www.bowdenshobbycircuits.info/r2.htm).  My values for the calculator were:
 
Input values
Voltage in (Battery)  =  7.5 Volts
Voltage out  =  4.0 Volts
Current= 0.01 amps (10 milliWatts)

Calculated results:
R1 = 300 ohms
R2 = 450 ohms
Power R1 = 0.03
Power R2 = 0.045

The bad news is that I didn't have these exact values  of resistors, but by combining 4 resistors I was able to finally come up with a circuit that didn't heat up when running the laser lights. 


Step 3: Build your Voltage Converter

Picture of Build your Voltage Converter
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Before you go off and build a voltage divider circuit from the calculated values, wire it up and test the output voltage.   I found that once I hooked up the laser lights the voltage dropped 1 volt and I had to change my resistor values to keep the voltage between 3.5 and 4.5.

I used perforated breadboard and terminal connectors to make the voltage divider easier to hook up.  I cut the board to size with a hacksaw and a vise. You can also make the mount for the laser lights this same way.

Solder the voltage divider and then apply some kind of protection to the back side to prevent against a short circuit.  I used hot melt, but electrical tape would work as well.
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Step 4: Build the Laser Mounts

1.  Insulate the laser light - I used a plastic tubing - like the type used on a water line to the ice maker on a fridge.

2.  Cut a piece of perforated breadboard to mount the laser on.

3.  Thread the laser light power wires through the mounting bread board.  

4.  Solder the terminal.  

5.  Apply hot melt to protect the solder joint from a short circuit and to hold the laser light straight.
 

Step 5: Mount the laser light to the L - bracket

Picture of Mount the laser light to the L - bracket
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Place a zip tie around the perforated breadboard to hold the laser light to the L-Bracket.

The screws will be used to mount the L-Bracket to the ceiling in the garage.  Bend the L-Bracket as needed to aim the laser light.

Step 6: Installation and Aiming

Picture of Installation and Aiming
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1.  Before mounting the system, test it!

2. Install the 2 Outlet Lamp Socket into the light socket of the garage door opener.

3. Mount the voltage divider - if you needed one

4. Mount the laser lights to the ceiling

5. Aim the laser lights.  
I aim them at the dash board just in front of the driver so that it can be seen as you are driving into the garage.