Bot’n Roll ONE A User Assembling Manual
4.2.13. BIPOLAR TRANSISTORS
A transistor is a semiconductor device used to amplify or switch electrical signals. On Bot'n Roll ONE A it
is used in the obstacles detecton circuit to increase the power of the light emitted by the infrared LED's.
It consists of three layers of semiconductor material of
P
and
N
types and has three terminals:
E
mitter,
B
ase and
C
ollector.
The provision of the three layers
P
and
N
set to
PNP
or
NPN
transistor.
When used as an amplifer, the current fowing between the
base and emitter (input) is amplifed and manifests itself
between collector and emitter (output). When the transistor
acts as switch, the base input signal toggles the output signal. Depending on the transistor
connecton confguraton, the amplifed or toggled signal in the output can be inverted or not,
regarding the input signal.
The two PNP BC557 transistors are placed on
Q1
and
Q2
.
These components are present in the infrared
emitter circuit, working as switches, allowing
the PIC18F45K22 to turn OFF and ON the
infrared LED's with high power. Thus, the
obstacles can be detected at great distances!
Transistors have polarity! Only work properly if placed correctly in the circuit.
You must match the fat surface of the transistor with the fat line on the board´s serigraphy.
©Copyright 2018, SAR - Soluções de Automação e Robótca, Lda.
27
Fig. 39: NPN bipolar transistor
Fig. 40: BC557B PNP Transistor
Descripton
Component
Q1
BC557 Transistor
Q2
BC557 Transistor
Summary of Contents for ONE A
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