2. The receiver



Click to enlarge


One part of the circuit is a stabilized +5V power supply which should be connected to an RCX output. It gives also the reference voltage (=2.5V) to the amplifier. The ultrasonic receiver is linked to the amplification stages, followed by the peak detector and a comparator to trigger the signal, which is then transfered to the PIC-microcontroller. (Use the oscilloscope and the RCX-beacon when calibrating.) The IR-detector's signal is dephased by 180°and then sent to the PIC. The output is the one we described already at the phase-sound's page. We added a 5th stage to the resistor-net. The relevant resistor has only 1kOhm. We use this small value for special messages. Don't forget to connect the optocouplers to an RCX input while observing the polarity this time. The PIC is clocked by a 4MHz quartz. The trigger point must be found through the potentiometer. 


Click to enlarge



C1 47uF
C2 100nF
C3 100nF
C4 47uF
C5 470nF
C6 10nF
C7 3300pF
C8 100nF
C9 22pF
C10 22pF
D1 1N4148
D2 1N4148
D3 1N4148
D4 1N4148
D5 1N4148
D6 LED3MM low current
IC1 LM324N
IC2 7805

  (CONRAD part No.171085, which

   is the TSOP1740 from Vishay Telefunken)
OK1 PC817
OK2 PC847
Q1 4MHz
R1 33k
R2 33k
R3 1k
R4 560k
R5 1k
R6 220k
R7 4k7
R8 22k
R9 100k
R10 10k
R11 1k or 330Ohm (test)
R12 10k
R13 1k
R14 680
R15 680
R16 680
R17 680
R18 680
R19 1k
R20 8k2
R21 15k
R22 33k
R23 56k
R24 2k2
R25 2k2
R26 10k
RCX connector
RCX_INPUT connector
T1 BC107


  receiver 40KHZ

  (Conrad part No.


NOTE: You may as well use the IR-receiver Sharp GP1U57X. Note that these IR-detectors only react on a modulated signal.



Here a typical receiver response:


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