RGB Color Controllable High Power LED Room + Spot Lighting

Step 15 Put a heatsink on the voltage regulators

the voltage regulators need a heatsink. the function of the regulator is to lower the voltage from the power supply to whatever the control knob indicates. the "dropped" voltage is burned up by the regulator and we need to get rid of the heat. this is the reason that the number of LED's in your strings needs to be close to the voltage of the power supply. if you used a 24V supply to power 1 LED, the regulator would need to drop 20V, or 80% of the power, and it would get very hot (and your setup would be very inefficient at making light). so we try to keep the voltage dropped by the regulator as low as possible - ideally, with the LED's at full power (about 3.8V per LED), we want the voltage on the LED string to be equal to the power supply voltage. in practice, the regulator has a minimum voltage drop (known as the "dropout"), of about 1 volt. on top of that, the current-limiter circuit drops 0.5 volt. so in practice we want the LED string at full power to be 1.5 to 2 volts below the power supply voltage, and this will result in maximum lighting efficiency and minimum heating of the regulator. conveniently, if the power supply is more than 5V above the LED string, we can just add another LED to the string, so this lets us get good efficiency for any power supply. overall, you will usually get 80-90% of input power to the LED's, and the controller will dissipate the remaining 10-20%. if you are building a 50-watt light like i am here, continue building as shown below. if you want your controller able to handle a full 360 watts of lights, you will need to put a heatsink on the regulators that can dissipate 50 watts.

- i didn't plan ahead! if i'd planned better, i would have been able to use my metal project box as the heatsink for the regulators. as it is, my circuit board sticks out past the side of the regulators so i can't attach them flat to the side of the project box.

- i'm using a chunk of the angle-aluminum for a heatsink, and i cut it so it would fit inside the project box. because of the convenience of using the project box as a heatsink, aluminum project boxes are ideal. as an alternative - if you have any old or broken computer power supplies around, these power supplies always have several heatsinks inside them which are the exact size for the regulators (TO-220 package) that we are using. even better, they will usually have heatsink insulators also.

- the metal tabs on the regulators are NOT electrically insulated. since we're connecting all three to a single heatsink, we need to insulate them electrically from the heatsink. you can find recycled heatsink insulators in an old computer power supply, or you can just use a piece of thin mylar (polyester) - refer to the LED mounting step for more details heatsink insulators.

- if you want to handle a full 300+ watt light, you'll need to use thermal compound here. you'll be putting up to 20 watts out of a single regulator. if you're only making a 50-100 watt light, just the silicone glue should be fine.

- using silicone glue: put glue on both sides of the insulator, and glue down the regulators. clamp them down until it is dry to ensure a good connection. after it is dry, also glue the heatsink directly to the circuit board so the assembly is rigid - you need to make sure the regulators can't pry themselves off the heatsink by accident.

- using thermal compound: drill holes in the heatsink to match the holes in the regulators. put thermal compound on both sides of the insulator. screw down the regulators using a nylon (insulating) screw, or else a metal screw with a nylon bushing around it (they are made specially for this purpose). see how much simpler it is to just use silicone glue?

- below i used the thermal-compound method.