28125 Parallax Inc, 28125 Datasheet - Page 303

• Manufacturer Part Number: 28125
• Description: TEXT ROBOTICS
• Manufacturer: Parallax Inc

Specifications of 28125

• Title: Robotics with the Boe-Bot
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

When you move the Boe-Bot in either direction indicated by the double-arrow, one or the
other IR pair will become focused on the electrical tape. When you do this, the readings
√
Now, place the Boe-Bot on the course so that its wheels straddle the black line.
The IR detectors should be facing slightly outward. See close-up in Figure 8-12.
Verify that the distance reading for both IR pairs is 0 or 1 again. If the readings
are higher, it means they need to be pointed slightly further outward, away from
the edge of the stripe.
Trouble Shooting the Electrical Tape Course
If you are unable to get a high zone value when the IR detectors are focused on the
electrical tape, take a separate piece of paper, and make a stripe that’s four strips wide
instead of three. If the zone numbers are still low, make sure that you are using 2 kΩ
resistors (red-black-red) in series with your IR LEDs. You can also try a 4.7 kΩ resistor to
make the Boe-Bot more nearsighted. If none of this works, try a different brand of black vinyl
electrical tape. Adjusting the IR LED/detector so that it is focused closer to or further from
the front of the Boe-Bot (see Figure 8-11) may also help.
If you are having trouble with low zone measurements when reading the white surface, try
pointing the IR LEDs and detectors further downward and toward the front of the Boe-Bot,
but be careful not to cause reflection off the chassis. You can also try a lower-value resistor
like 1 kΩ (brown-black-red).
If you are using the older shrink wrapped IR LEDs instead of the ones with the 2-piece
plastic shields, you may be having trouble with getting a low zone number when the IR
LED/detectors are focused on the white background. These LEDs may need 470 Ω (yellow-
violet-brown) or 220 Ω (red-red-brown) resistors in series. Also, make sure that the leads of
the IR LEDs are not touching each other.
Electrical Tape
Figure 8-11
Test for High
Zone Number
– Side View