HP48SX IR DECODER

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INSTRUCTONS FOR THE HP48SX IR DECODER

 1) The circuit diagram is attacted to this message, as a printable  
 ASCII TTYpic. It should be printable on _any_ printer. 
 2) Construction and layout is not critical and any metohd should work. 
 I used Verowire self-fluxing wiring system. I also socketed all the IC's, 
 but that too is up to you! 
 3) De-coupling capacitors and power connections are not shown on the circuit 
 diagram. Place a 0.1uF ceramic capacitor across the power connections on each 
 IC. Also place a 10uF tantalum capacitor across the power connections close 
 to the IR transmitter. 
 4) The IR LED and IR phototransistor should be mounted on the front panel of 
 the unit. The LED goes on the Left, looking at it from outside. They must line 
 up with the ones on you HP48 for transmission to occur at all. The range of the 
 unit is about 2".  
 5) The IR LED and phototransistor are critical. I used ones available from 
 MAPLIN (see my earlier messages for the address), but the equivalents are: 
 Phototransistor Maplin YY66W (Infra Red Sensor) = TIL78 
 LED             Maplin YH70M (Infre-Red Emitter) = TIL38 
 6) The RS232 port links to the PC, not to the HP48 of course. 
 7) The circuit as given requires a +5V supply only. The MAX232 device (which 
 is expensive and hard to obtain) can be replaced by a 1488 (transmitter) 
 and 1489 (receiver) devices but then +/-12V are required for the 1488 
 8) Each section of multiple ic's is numbered. 'xx means 74lsxx. A total 
 list of ic's required is: 
 MAX232, 2*74ls393, 7425 (or 74ls25 if you can get one!), 74ls74, 74ls08, 74ls14 
 74ls04. 
 9) A list of symbols used is: (as some are non-standard to get them into 
 printable ascii) 
 -\/\/--    resistor 
 ! 
 \ 
 / 
 \    resistor 
 / 
 ! 
   
   !! 
 --!!-- capacitor 
   !! 
    !--! 
   +!  !+ 
  -!!  !!-   Quartz Crystal 
   +!  !+ 
    !--! 
 !/ 
 !     NPN transistor 
 !\! 
  - 
 \\ 
 >> 
 ! / 
 !/ 
 !\    IR phototransistor 
 ! \! 
  - 
  ! >> 
  V// 
 ---  IR LED 
  ! 
  !\ 
 -! >o-   NOT gate 
  !/ 
 -!\ 
  ! )-   AND gate 
 -!/ 
 -) 
  ) 
 -)--\ 
  )   >o-- NOR gate 
 -)--/ 
  ) 
 -) 
   +5                
   ---- 
    !                       ----------------------------- 
    !                       !                           ! 
    /                       !                 ----+     o  '74 
    \ 10k              '04  ! '04   '04   '08 /// ! --------- 
 \\ /        !\        !\   ! !\    !\            +-!D  S   ! 
 >> !--------! >o---+--! >o-+-! >o--! >o--!\        !      Q! 
 ! /         !/     !  !/     !/    !/    ! )-+     !       !o------+ 
 !/ IR       74ls14 ----------------------!/  !  +- !>  R   !       ! 
 !\  P/transistor                             !  !  ---------       ! 
 !_\!                                         !  !      o   +5      ! 
    !              ----------------------------  !      !  ----     ! 
    !              !                             !      !   !       ! 
   ---             !                             !      -----       ! 
   ///             !                             !                  ! 
            '393   !        '14                  !                  ! 
              ----------    !\                   !                  ! 
              !    R   ! +- ! >o-+     '25       !                  ! 
              !       A!-+  !/   +-----)         !                  ! 
              !        !               )         +---+              ! 
              !       B!---------------)--\    !\    !              ! 
          +---!>       !               )   >o--! >o--+              ! 
          !   !       C!---------------)--/    !/                   ! 
          !   !        !               )       '14                  ! 
          !   !       D!---------------)                            ! 
          !    ---------                                            ! 
          +-----------------------------------------------------+   ! 
                                                '393     '393   !   ! 
                 2.45MHz                       !----!   !----!  !   ! 
         '04     !--!       '04         '04    !   A!   !   A!  !   ! 
         !\     +!  !+      !\          !\     !   B!   !   B!--+   ! 
     ----! >o-+-!!  !!--+---! >o-----!--! >o---!>  C! +-!>  C!  !   ! 
     !   !/   ! +!  !+  !   !/       !  !/     !R  D!-+ !R  D!  !   ! 
     !        !  !--!   !            !         !----!   !----!  !   ! 
     !  1k    !         !  1k        !          !        !      !   ! 
     -/\/\----+  2n2    --/\/\-------!         ---      ---     !   ! 
     !           ! !                 !         ///      ///     !   ! 
     ------------! !-----------------+                          !   ! 
                 ! !                                            !   ! 
    +5                                                          !   ! 
   ----     !!        !! 4*22u                                  !   ! 
    !     +-!!-+    +-!!-+                                      !   ! 
    !     ! !! !    ! !! !                                      !   ! 
    !     !    !    !    !                                      !   ! 
    !    -------------------                                    !   ! 
    !    !  C1       C2    !  +---------------------------------)---+      
    +----!Vcc              !  !                                 ! 
   ---   !                 !  !                                 !  +5 
   ---+  !                 !  !                                 ! ---- 
    +----!+10v             !  !                                 !  !  >> 
         !                 !  !   +-----------------------------+  V // 
  PC     !                 !  !   !    '393                       --- 
 RS232   !                 !  !   !   !----!                       ! IR 
   >-----!TxO1         TxI1!--+   !   !   A!              +-/\/\---+ LED 
  Tx     !                 !      !   !   B!       2N3904 ! 56R 
         !TxO2         TxI2!      +---!>  C!            !/ 
         !                 !  +-------!R  D!----/\/\----! 
   >-----!RxI1         RxO1!--+       !----!    1k2     !\! 
  Rx     !                 !                            - ! 
         !RxI2         RxO2!                              ! 
         !                 !                             --- 
   >--+  !  -10V     Gnd   !                             /// 
  Sg  !  ------------------- 
      !       !  !!  ! 
      !       +--!!--+ 
      !          !!  ! 
     ---          +  ! 
     ///             ! 
                    --- 
                    /// 

 ------------------------------------------ 
 ------HP IR FORMAT BELOW------------------ 
 ------------------------------------------ 
 Taken from ioguide.doc, ftp from 
 ftp hpcvbbs.cv.hp.com, dir pub 
 The IR port allows half-duplex communication between  systems  at 
 2400  baud  using  pulses  of  infrared  light  instead of wires. 
 Full-duplex is not used due to the need to suppress  reflections. 
 The  format for IR transmission is similar to serial transmission 
 except that a pulse of infrared light of 52 Ns duration (nominal) 
 is used to transmit a zero-bit.  The absence of a pulse indicates 
 a one-bit or  idle  condition.   Note  that  if  the  pulses  are 
 stretched out to fill a bit time this becomes very similar to the 
 serial signal. 
  

Source

  • ARD[at]siva.bris.ac.uk

Category:InfraRed

 

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