It was recommended that I check out
the IS471F for a no contact bump sensor. I picked up a bunch and
started experimenting.
The IS471F has a IR LED driver
built-in. It is modulated at 38Khz to match the built-in detector.
The module will output a high if no object is detected and a low if and
object is detected. You wont get any range with this sensor
but it's a very fast go/nogo test makes for a great bump sensor that can
be placed around the circumference of your bot.
I tried various resistor values in
series with with the IR LED I was using. At 390 ohms you get a 1-2"
distance detection. With 100 ohms I got over 5". There must be
some sort of current limiter because while the detector still works the
distance remains at 5".
One of the problems I had was figuring
out what is the front of the module from the data sheet. I took a
picture of both sides of the module with the correct numbers of the leads
from ether side. Side A is the detection side of the module.
 |
 |
|
Side A |
Side B |
The module is set for optimum
detection at 940NM. The IR LED should be the same.
Hookup
Schematic 1
This program will
light a led when ever a target is detected.
Program
'IS471F Demo
output 6
low 6
loop:
if inp0 = 0 then
high 6
else
low 6
endif
goto loop
Final thoughts.
You will need to shield the IR LED from the module with small piece of
electrical tape. If stray IR from the modulated LED strikes the
sensor module it will not work correctly.
What else can you do?
By connecting 8 of these sensors to a 74HC165 shift input register you can
use just a couple of pins to monitor 8 IR bump sensors.
Parts
Easy RS232 Driver
Athena
IR Emmitter LED
7.5V AC Adapter
9 Pin Cable
Breadboard and
Wire Kit
Breadboard
Regulator
IS47IF Sensor from Digi-Key
part # 425-1178-5-ND
