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c) Photo transistors & IR LEDs
Prior to soldering in, the photo transistors T1 and T2 must be covered with a piece of shrinkdown plastic tubing (approx. 1 cm long). This prevents
the influence of external light from the side. The shrinkdown plastic tube can be shrunken with a special hot air blower or a cigarette lighter.
Photo transistors T1 and T2
For the IR LEDs D6, D7, D8, D9, D10 and D11, the same applies as for T1 and T2. These also have to be covered with a shrinkdown plastic tube
(approx. 1 mm long) prior to soldering in.
However, with the IR LEDs, this has a different purpose than with the photo transistors. The shrinkdown plastic tubing prevents that the
TSOP1736 sees the IR signal directly and restricts the radiation beam of the diodes somewhat.
IR LEDs D6, D7, D8, D9, D10, D11
d) Wheel sensors
The LED and the photo transistor (reflex light barrier for the optometry) that point in the direction of the first transmission wheel, need a
correspondingly marked disk to be attached on the first transmission wheel (that with the 50 and 10 teeth), on the side without the drive pinion.
These disks are self-adhesive.
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The more segments the pattern has, the more exact you can resolve the rotation of the gearwheel and thus the speed of the PROBOT. However, the measured difference between light and dark is also reduced then. As a consequence, there may be problems or
failures in detecting the rotation speed.
We always used a division of four in our assembly. We recommend highlighting the black segments with a water-proof pen to obtain
a better contrast.
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