Page 82 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Out B
2
Out A 1 14
13
Vcc
Vcc 3 12 GND
U Ref 4 – 3 2 A D
U IN + – + – +
5 12
4 11
5 10
6 – B + – C + 9

7 8

LM 339
Quad Comparator
Vcc 2–36 Vdc or ± 18 Vdc
5.1 Comparator and LM 339 quad comparator IC

61
Vcc Vcc
R1
Vref
Vref Vref
R2

A B C
5.2 Voltage dividers A, B, and C

Voltage divider

The voltage divider is a simple but important concept. When using it,
you will be able to connect most resistance-type sensors to a com-
parator. The reference voltage is derived from a voltage divider made
up of two 10K-ohm resistors (see Fig. 5.2A). The Vref in this case will
be half of the supply voltage (Vcc) of 5 V, or 2.5 V (see Table 5.1). We
can make Vref any voltage we require between ground and Vcc by
adjusting the two resistance values of the voltage divider.

Team LRN Sensors