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Wiring the LEDs for FTIR

I contemplated making my own PCB boards for the LEDs, but after doing some searching I found some boards online that would be more cost effective and work better than making my own boards. I decided to buy the following board from futurlec.com It’s possible to get 4 individual strips from each board for making individual LED PCBs. I needed a total of 10 strips for the two sides of my acrylic so I purchased 3 boards for $9.50. The strips are good because they will allow for 4-8 LEDs per strip. I chose to do 5 LEDs with a 1ohm resistor per strip (@ 7.5v), making a total of 25 LEDs per side of my acrylic.

The LEDs I’m using are the popular OSRAM SFH485 bought from digikey.com, but you can find them from many places.

PCB board

Parts to cut out from PCB board using a utility knife or guillotine

PCB boards cut from the main board

Another view of the individual PCBs

The LEDs soldered to the board. The green wire connects each (-) to the (+) of the next LED.

Another view, this time with the leads cut off the LEDs. LEDs are about 1 1/4″ apart

After wiring all the individual PCB boards. I started connecting all the positives from one board to the positives to the next. I did the same thing with all the negatives. The picture below looks more complicated then it really is.

The LEDs on the side of the acrylic.

All the LEDs wired up and set aside the acrylic

Although it doesn’t look very “clean,” all the wires will be hidden within the top frame. The LEDs will be attached to the bottom part of the top frame and the top and bottom parts of the top frame will screw into each other leaving the LEDs hidden inside.

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  • Jan-Lennert

    Hi, I wass wondering why you use led’s?

  • matt

    some body tell me why i shood use LEDs

  • cerupcat

    Because I’m using a multitouch technique called FTIR. It requires LEDs to be shined into the side of acrylic. There’s more information on the rest of my blog.

  • Sergio

    How did you turned your leds to the power supply? Did you use a computer power supply?

  • Nelly

    Sergio said:
    How did you turned your leds to the power supply? Did you use a computer power supply?

    I think you need to check if your computer’s power supply has an empty slot for an additional molex connector then you buy 1 molex connector and rewire the + & – to the black (ground wire) and yellow.

    Hey Seth, how can you wire 96 IR LEDs into one PC power supply? i seperated them into groups of eights for the 1.5V each, but i ain’t sure how to get all 96 of them connected, do u think i should you more than 1 power supply?

  • Nelly

    oh by the way its an FTIR table and on that last sentence i meant, “do you think i should use more than 1 power supply” ? thanks

  • Romeu


    The images not found, please check .