Optical obstacle switch - del50006
This is a simple toy that has many applications. Any object that
breaks a light beam will trigger a relay to on condition for a
period of time.
Description - The 555 monostable has a 1 second period, If pin 2
gets low trigger pulses of a frequency more than 1 Hz, the
output pin 3 will remain high, if the trigger pulses came in 10
second delays then output will go on and off, so also the relay
and the electrical load on relay contacts. Like an integrator,
it will not operate relay very fast. Even in a fridge stabilizer
they put something like this else the compressor motor is
damaged on frequent black-brown outs.
Retro-Reflective Proximity Switch
Now for the LM567 part, The clock at pin 5 flashes the IR
Transmitter LED LD1 at a frequency set by C7-R5. The IR Photo
Sensitive Diode or Transistor LD2 conducts when light is got
from the IR LED. As the lights is in pulses, so also the
impedance of LD2 goes low and high at same frequency.
This develops an AC waveform across R3 over a DC representing
Ambient light. If direct sunlight falls on this arrangement, the
Photo-diode saturates, then this circuit or any other circuit
won't work. But when ample protection from ambient light
is made, some pulses good enough for LM567 tone detection, 100mV
rms, is obtained and it operates the relay via a LM555.
Layout Hand-Made Artwork
Right Click Image, Save to Disk, Print to Scale.
Build it Yourself.
The Artwork was made by a traditional PCB Artist with Artwork
tape, pads, Rotring Pen, and Knife. This is scan of Hand-Made
Artwork. Then we go to a Offset printing, photo processing
studio, he will make a Positive and Negative of artwork with
photography. This is what you will need to make a PCB. Positive
Film and Solder Mask.
switch with photo sensors
The Artwork and Film are 1:1 or 1x, 300dpi scan. The Solder Mask
is shrunk to 1/2, it may not be usable, i have to still build
some graphics expertise and using the scanner. The component
layout is an assembly instruction. I have no idea how you will
make PCBs out of this, try postscript printing or ask a DTP
But if you manage to get a scaled print, and you know screen
printing or even have a photo resist fluid. you can make
prototypes at home. I used to do it in my younger days.
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