Message #3387 - comp.robotics 
   Date: 02-23-93  5:13
   From: Bob Lee
     To: All
Subject:: IR proximity detector - schematic
-------------------------------------------------------------------------------
@PID: Fred 1.9.h
@MSGID: 1:124/2206.0 2f197567
@Organization: Bowling Green State Univ.
@Message-ID: <C2vyJC.AMz@andy.bgsu.edu>
@
===================
IR DETECTOR CIRCUIT
===================


                           30Hz BANDPASS FILTER          gain = 1
                                                            Q = 4


        +5V                  .1uF
         |                    ||            330K
         \            +-------||----+-------/\/\/--------+
         /            |       ||    |                    |
         \ 100K       |             |                    |
         /            |             |                    |
         \            |             |                    |
         |            |      .1uF   |     ___            |
         |     39K    |       ||    |    |   \___        |
         +----\/\/\---+-------||----+----|-      \___    |
IR       |            |       ||         |           \   |
Detector |            |                  |   LM3900   >--+---+
         |            |                  |        ___/       |
    ||---+            \             +----|+   ___/           |
    ||                /             |    |___/               |
    ||---+            \ 5.6K        \                        |
         |            /             /                        |
         |            \             \ 1M                     |
         |            |             /                        |
         |            |             \                        |
        GND          GND            |                        |
                                   +5V                       |
                                                             |
                                                             |
                                                             |
                        +------------------------------------+
                        |
                        |
                        |
                        |
                        |
                        |                  ___
                        |        120K     |   \___
                        +-------\/\/\-----|-      \___
     SCHMITT TRIGGER                      |           \
                                          |   LM3900   >--+------ Vout
                                          |        ___/   |
                                     +----|+   ___/       |
                                     |    |___/           |
                                     |                    |
                                     |                    |
                           1.1M      |         1.1M       |
                     +5V --\/\/\-----+---------\/\/\------+
                                                          |
                                                        ----- 1uF
                                                        -----
                                                          |
                                                          |
                                                         GND

NOTES:
~~~~~
- The LM3900 is a quad unipolar op-amp IC. Vcc of this chip must be on +5V
DC.
- I found that the 100K pull-up resistor on the IR detector provided the
optimum
  sensor performance. Any increase or decrease in the resistance caused a
  decrease in the signal quality from the IR detector.
- The 0.1uF capacitors that are part of the filter eliminate the effects of
  DC light, such as direct sunlight, something that causes an unfiltered IR
  passive detector to become swamped.
- The H->L and L->H threshold voltages in the Schmitt trigger can be changed
by
  adjusting the 120K and 1.1M resistors.
- The 1uF capacitor was added to eliminate voltage spikes at the H->L and
L->H
  trasitions.
- Vout is a TTL/CMOS level signal that outputs a logical high 30 times/second
  when an object has gotten within 6-12 inches of the IR detector.





==================
IR EMITTER CIRCUIT
==================


                    +5V                            555         +5V
                     |                            TIMER         |
                     /                        +-----------+     |
                     \                       1|           |8    |
                     / 10ohms        GND -----|GND     Vcc|-----+
                     \                        |           |     \
                     /                        |           |     /
                     |                       3|           |     \ 2.2K
                     +------------------------|OUT        |     /
                     |                        |           |7    \
                     |                        |      DISCH|-----+
                     |                       4|-          |     \
         IR LED  ||--+               +5V -----|R          |     /
                <||                           |           |     \ 200K
                 ||--+                        |           |     /
                     |                       2|           |6    \
                     |                    +---|TRIG  THRES|-----+------+
                     |                    |   |           |     |      |
                     |                    |   +-----------+     |      |
                    GND                   |                     |    -----
.1uF
                                          |                     |    -----
                                          +---------------------+      |
                                                                       |
                                                                      GND

NOTES:
~~~~~
- Adding more IR LED's will increase the range of the IR detector.
- The signal on pin 3 of the 555 is 30Hz and has a duty cycle of 50%
- Due to the very small pull-up resistor the 555 sinks about 109mA. The specs
  say the 555 can sink up to 225mA so it's well below the danger level.

---
 * Origin: Dallas/Ft.Worth Usenet Gateway (1:124/2206.0)
@PATH: 124/9999