LED Floodlight - Roomlight

This is a 12 volt 102 LED floodlight project using very simple components and relatively simple construction. It uses commonly available ultra bright straw hat LED's which are cheap. As we are not using any high power LED's the amount of heat generated is negligible thereby eliminating the need for heat sinks. The main features of the project are listed below:

1. Uses commonly available cheap straw hat LED's
2. Doesn't require a costly LED driver as we use resistors to limit current
3. Light works on 12V and hence can be used with solar or wind power systems without an inverter
4. No need of heat sinks as the amount of heat generated is low
5. Very bright and gives enough light for a normal sized room

I have included the parts list, detailed instructions and printable stencil image to drill the holes for mounting LED's.

Parts Used

Ultra bright straw hat white LED's - 102 nos

White coloured 10" * 4" PVC plate - 1

100 ohm 1/4 watt resistor - 34 nos

Hook-up wire and an on-off switch

Tools Required

Drilling machine and 0.5mm drill bit or 1mm drill bit

Soldering iron, solder and flux

The PVC plate is commonly used for switch box covers in household wiring and I think will be available in hardware or electrical stores. The reason behind selecting PVC is because we can drill very clean holes close to each other with sharp edges without much difficulty and as it is white will help in reflecting light and also gives a clean look to the finished light. If PVC plates are not available then acrylic or plastic sheets can be used but should have at least 3mm thickness to ensure that it wont break during drilling.

If the voltage of the battery or the source we are going to use for this light goes above 12V then its better to increase the resistor value to 150 ohm and it will ensure maximum life of the LED's. I have used 100 ohm resistors as I will not be using the light when the battery is getting charged and also there is some voltage drop due to the 30 meter long wire used to connect the battery to the light.

On-Off switch is optional, if you want to mount the light to a height more than what you can reach by standing on the floor then its better to avoid the switch on the light and wire one below next to the battery.

The most tedious part of the project is to drill 204 holes on the plate, 2 holes per LED for mounting the 102 LED's. I have used a Bosch Li-ion small screwdriver cum drill with 1mm drill bit for the process. But I would suggest using a high speed drill with 0.5mm bit for faster drilling. Take a 100% scale print out of the hole template and glue it on top of the PVC plate and drill the holes - two per LED.

Once the drilling is finished the project is half done as it was the most time consuming task. Now we can remove the printed paper template from the PVC plate. It can be washed with soap and water to remove any residue of glue or paper. Now its time to mount the LED's.

We are going to connect three LED's in series and 34 such series connected strings in parallel. For every series connection we will add one 100 ohm resistor. It is advisable to test each and every LED before soldering on to the plate to avoid re-soldering if one is not working. Use the stripped hook-up wire to interconnect the LED's.

Insert the leads of each led through the holes after watching the polarity and bend both the leads to opposite directions from the bottom of the plate. This makes sure that the LED stays in position and no need to glue the LED to the plate. Check the pictures to understand how this is done.

The -12V line is all around the board connecting resistors on the two sides of the board and the +12V line is ran through the center of the board connecting all the positive leads of all the 34 strings together.

Here we are using the resistors to limit the current to the LED's so that it will not get damaged when connected to a 12V battery. By varying the value of the resistor between 100 and 150 ohms the brightness of the LED's can be changed.

One problem I have faced with the light is that I cannot look into the light directly as it is too bright. To solve that problem we can add a diffuser to the light.

Fix double sided foam tape all around the four corners of the plate and then use a white colored polythene plastic sheet of the same size of the board to cover. Stick one side at a time to the tape and pull the other side to fix the sheet without any wrinkles. I think the best material to use will be white acrylic sheet designed for use as diffusers, but polythene sheet is a cheap alternative.

The light can be connected to any 12V DC source, but if connected to a rechargeable battery make sure that the battery voltage is not going below 10.5 V to prevent damage to the battery. This is because the light will continue working with lower voltages of even 9V and if we are not switching off the light when the battery voltage drops below 10.5 then it could damage the battery.

A good setup can be created by connecting the light to a solar charge controller and hooking up a 12V 7AH rechargeable battery. The solar charge controller will disconnect the load when the battery voltage drops below a certain level. Add a 10W 12V panel to this and we get a solar powered LED floodlight.

The current consumption of this light is around 700mA at 12Volt.

Please let me know for any suggestions/doubts/feedback.