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ELM337 데이터시트 PDF




ELM Electronics에서 제조한 전자 부품 ELM337은 전자 산업 및 응용 분야에서
광범위하게 사용되는 반도체 소자입니다.


 

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부품번호 ELM337 기능
기능 LIGHT SWITCH
제조업체 ELM Electronics
로고 ELM Electronics 로고


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ELM337 데이터시트, 핀배열, 회로
ELM337
Light Switch
Description
The ELM337 provides a convenient means to
interface standard photocells or light dependent
resistors (LDRs) to digital logic circuits. It provides
an input comparator with hysteresis, line frequency
filtering, digital delays, and high current output
drivers all within the one 8 pin package.
Three mode setting pins configure the ELM337
for pulse or continuous output and for a delay on
change of from 1 msec to 10 minutes. The transition
threshold is set with a single external resistor,
simplifying designs and minimizing costs.
www.DataSheet4UA.cpoplmications need not be limited to those
employing photocells, as the Example Applications
section shows. The Schmitt trigger input provides a
convenient way to interface to virtually any input
signal, whether from digital logic or from a slowly
varying analog source. The remainder of the
ELM337 can simply be thought of as a time delay on
pickup and dropout type circuit - very useful for
sequencing processes.
Applications
• Automatic lighting controls
• Security light beam monitoring
• Position sensing
• Light controlled counters
• Time delay circuits
Features
• Low power CMOS design - typically 1mA at 5V
• Operates from 3V to 5.5V
• No external timing elements required
• Low parts count
• Digitally selected delays of up to 10 minutes
• Pulsed or continuous outputs
• Internal line frequency filtering
• High current drive outputs - up to 25 mA
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
M2 2
M1 3
M0 4
8 VSS
7 Light
6 Dark
5 LDR
Block Diagram
LDR 5
Line
Frequency
Detector
Programmable
Timer
234
M2 M1 M0
Output
Logic
7 Light
6 Dark
ELM337DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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ELM337 pdf, 반도체, 판매, 대치품
ELM337
Example Applications
Figure 1 at right shows the ELM337 installed in a
typical lighting control circuit. The mode has been set to
111 (or HHH), resulting in delays of 10 minutes when
recognizing a light or dark condition. In this case, only
the ‘Dark’ output (pin 6) is used to enable (and disable) a
lighting circuit, but other variations on this theme might
use the Light output (pin 7), or possibly use mode 110 to
provide short (50 msec) output pulses to trigger other
circuits.
The threshold setting resistor (22kin Figure 1) is
chosen depending on what resistance it is desired to
have the transitions to light or dark occur at. Using the
typical Schmitt voltage thresholds for a 5 volt supply, it
can be shown that the two resistances that switching will
www.DataSheeotc4cUur.caot mare 1.33RT (light to dark) and 0.37RT (dark to
light), where RT is the threshold setting resistance. For
the 22kshown, these would be at about 30kand
8k, respectively. The values that you choose would
depend on the LDR used, and your application.
If the LDR (Rλ) is mounted more than a few feet
from the ELM337, the increased exposure could cause
problems due to induced voltages and currents. To
provide protection from these, a resistor (Rprot) should be
added in series with pin 5 as shown at right. Typically
this resistor would be equal in value to the threshold
setting resistor.
To the
controlled
circuit
8765
+5V 1
337
23
4
0.01µF
+5V
22K
start
Figure 2. Time Delay Dropout Switch
+5V
0.01µF
18
27
36
45
RT
22K
To the
lighting
circuit
Rprot
(see text)
Rλ
Figure 1. Yard Lighting Controller
The ELM337 is also capable of operating simply as
a delay circuit. By hard-wiring the mode pins for a
desired delay, and applying logic levels to the LDR pin,
symmetrical output delays of up to 10 minutes can be
obtained.
Asymmetrical delays can also be obtained as shown
in Figure 2. This circuit connects the ELM337 to provide
a 50msec delay on pickup and 10 second time delay on
dropout function.
Operation of the circuit can best be explained as
follows. When the ‘start’ pushbutton is pressed, the M2
and M1 pins will both be at a logic low level, while M0 will
be high. The LDR input is also at a low level, simulating
an LDR that is just ‘seeing’ light. Since the mode is 001
or LLH, then from Table 1 (on page 2) the Light output
will go to a high level after 50msec. This delay is
desirable as it ensures that the input is legitimate by
providing some degree of switch debouncing.
As soon as the pushbutton is released, the M2
mode pin returns to a high level, and what appears to be
a dark input will be on the LDR pin. From Table 1, with
mode 101, the output will turn off after 10 seconds.
Certainly several other variations are possible by
connecting the mode pins in different combinations. Why
not try your hand at some…
ELM337DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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