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Hardware

The Circuit:

IR Link Circuit

Notes on the schematics:

  • The xtal shown is not a xtal, it is an 4MHz resonator(my drawing program does not support resonators). The resonator has 3 pins, and the middle one has to be connected to the ground. The resonator is a xtal with built in capacitors; if you can't find a resonator, you can replace it by a xtal with two 15pF to 33pF caps.
  • The ground of the calc should be connected to the ground of the link.
  • The circuit can be powered from a 9V battery together with a 78L05 +5V voltage regulator(and 2 protection caps), or directly from the 4.5V flat battery. A 4.5V battery has a long life and is cheap, but a 9V one is more portable. Personally I prefer 4.5V batteries.
  • A PIC16C84 of a PIC16F84 can be used. However a PIC16F84 is better and cheaper. When programming a PIC16F84, make sure you set the fuses to: XT, WTD_ON and PWR_ON. You can also have Pre-Programmed PICs from me.
  • Don't forget to download the LITE code for the PIC from the Software downloads section.
  • In the LITE version there is only 1 switch on RB7. The other switch is only useful in the STANDART version.
  • R10 and R11 are new. They are pull-up resistor that are needed on some calcs(some old calc versions does have them built-in) and are also needed if the cable is long.
  • Parts:

    The values of the components:

  • R1: 330 Ohm
  • R2: 1 kOhm
  • R4,R6: 80 kOhm
  • R3,R5: 600 kOhm
  • R7: [There is no R7]
  • R8: 470 Ohm
  • R9: 120 Ohm, this one depends from the IR LED.
  • R10,R11: 44K Ohm.
  • C1: 4.7 uF
  • C2: .1 uF
  • Resonator: 4MHz
  • D1: IR LED, see text.
  • D2, D3: 1N4148
  • D4: Any RED LED.
  • SFH506: IR Reciever: SFH506-30


    The IR reciever module:

    The essential part is the SFH506-30 from Siemens. This one operates at 30khz.
    It may be hard to find Siemens parts in the US. Here
    is a link to Siemens distributor in the US:

      http://w2.siemens.de/semiconductor/logistic/distrib/usdisti.htm

    This module is compatible with SFH505A also from Siemens (this one isn't more produced) and the IS1U60 from Sharp. Take a look at the Datasheet of the SFH506 to see the pins description.

    The IR LED: Any IR LED that has a wavelength of 950 nm can be used instead of the SFH415 from Siemens. In the Datasheet of the SFH506-30 they say that with the SFH415 a range up to 34 m can be obtained.

    Extending the range:
    To extend the range, multiple IR LEDs can be connected in parallel, the same way as D1 is connected. Like this:

    Circuit



    Resetting:
    To reset the PIC you have to unplug it from the calc and from the power, or you can add a simple push button this way:

    Reset circuit


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    Author : Sami Khawam

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