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DMS APPLICATION NOTE

Decimal Point Drivers

DMS APPLICATION NOTE
Decimal Point Drivers
The most common technique for activating a single decimal point is simply tieing its activation pin to ground. In most situations, only one decimal point is used because the display reading represents only one parameter. However, some applications require the use of more than one decimal point in order indicate a different range, or perhaps, have the reading represent some other system parameter. A simple rotary switch can be used with any DMS meter when two or more different decimal point selections are required. The rotary switch method is illustrated in Figure 1. Other components that can be used for decimal point drivers, particularly when dynamic control is required, are TTL or CMOScompatible logic gates / buffers and open-collector / open-drain discrete transistors. The maximum current the driving device must sink is 20mA (see individual product data sheets for more specific data). The following diagrams illustrate the various techniques that can be used for driving the decimal points on all DMS Series meters.
11 (+) IN HI
DMS-30PC
8 REF OUT
11 (+) IN HI
DMS-30PC
8 REF OUT
12 (-) IN LO 1 +5V SUP 3 GND 4 DP3 5 DP2 6 DP1 7 REF IN
+5V (ON) 0V (OFF)
Figure 1. Simple selector switch can be used with all DMS Series panel meters.
DMS-40LCD-X / X-5
11 (+) IN HI
DMS-30PC
8 REF OUT
11 (+) IN HI
12 (-) IN LO 1 +5V SUP 3 GND 4 DP3 5 DP2 6 DP1 7 REF IN
12 (-) IN LO 1 +5V SUP +5V (ON)
Q1 4.7k
Q1-Q3 2N2222
0V (OFF) U1A
4.7k +5V (ON) 0V (OFF) 4.7k
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DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.