LED Illuminated Drill Stand

Having started with my own home-made printed circuit boards again, I invested into a drill stand which transforms a small hand-drill into a precision drill press. But working with small details is easier when there is enough light, but how do i get it to the right place?

I constructed a 12V LED ring light with the right dimensions to mount it on the lower side of the drill stand. This instructable will show you the details.

Material:

• 12 white 3mm LEDs
• 4 SMD 100ohm resistors
• circuit board
• some wires
• 12V power supply

Based on the common design of 12V LED ribbons I decided to use segments of 3 white LEDs in series with a current limiting resistor and then use four of these sections to cover a full circle. I designed the circular PCB in the free version of Cadsoft's Eagle. In the PDF you will find a 1:1 scaled version of the layout.

Using 3mm white LEDs running at around 20mA each with a voltage drop of about 3.2V per LED gives you the value for the current limiting resistor as R=(12V-3*3.2V)/20mA or approximately 100ohm. I had to use SMD resistors because of the limited space on the circuit board, while I chose standard 3mm through-the-hole LEDs because I happen to have a large stock of these.

I etched the PCB for the LED ring light using the laser toner transfer process. There are several instructables covering this topic, e.g. PCB making guide. Based on my own experience and the tip from my students, the glossy photo paper available at the Swedish chain Biltema works best.

After cutting out the circular part of the circuit board using a fretsaw I first tin-plated all copper traces. Then I mounted the four SMD resistors and finally the twelve 3mm LEDs.

In order to attach the LED ring to the drill stand I used double-sided adhesive tape - the foam type, which is necessary to compensate for the lack of flatness of the soldered PCB. Cutting back the sticky tape with a scalpel is not as easy as it might sound, because the tape will stick to everything, including the blade itself.

Finally I could attach the lights to the drill stand and enjoy the comfort of an illuminated drill spot.

Using SMD LEDs and resistors would have the advantage of offering a flat backside of the PCB which allows for easier mounting. However, the more focused light emission of the 3mm LEDs can be advantageous when it comes to the illumination of the drill spot.