LS7217_14 Datasheet, PDF (1/6 Pages) LSI Computer Systems – PHOTO CONTROLLED OUTDOOR LIGHTING WITH PROGRAMMABLE TIMER

LSI/CSI
LS7217
LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 [phone] FAX [phone]
PHOTO CONTROLLED OUTDOOR LIGHTING WITH PROGRAMMABLE TIMER ^{Sep 2014}
FEATURES:
• Input interface to a LDR or a photo transistor
• Programmable Duration Selection
• Shunt regulator
• 50Hz / 60Hz time base selection
• Relay Driver output
• 6.0V ± 0.75V operating voltage range (VDD – VSS)
• LS7217 (DIP), LS7217-S (SOIC) – See Figure 1
PIN ASSIGNMENT
APPLICATIONS
Lighting control for outdoor area lighting, street lighting, parking lot
lighting, billboards lighting
DESCRIPTION
The 7217 is a programmable Timer IC designed to turn on a relay at
night and turn off the relay at dawn or after a selectable number of
hours. Figure 2 shows a typical application schematic.
PIN DESCRIPTION:
The following describes the operation of the inputs and outputs of the
IC.
VDD (Pin 2)
VDD is the supply voltage positive terminal. It is regulated internally in
the IC. The internal voltage regulator produces 6.0V ± 0.75V.
FIGURE 1
The Time Select Table is as follows:
TS1
TS2
Time Duration
0
0
4 Hours
0
1
6 Hours
1
0
8 Hours
1
1
Dusk-to-Dawn
Dusk-to-Dawn duration is determined solely by the photo-cell; i.e.,
the Relay output is on whenever the photocell recognizes an ambient
dark condition.
VSS (Pin 6)
VSS is the supply voltage negative terminal.
50Hz / 60Hz SELECT Input (Pin 8)
A high at this input selects the correct timing for 50Hz operation.
Floating this input selects the correct timing for 60Hz operation. A
low at this input places the LS7217 into Test Mode where the
timeouts are accelerated by a factor of 60.
50Hz / 60Hz Input (Pin 7)
This input is the clock source for all timing functions. This input has a
Schmitt trigger to ensure a clean internal clock waveform.
TIME SELECT Inputs TS1, TS2 (Pins 4, 5)
The two Select inputs determine the time duration that the Relay
output stays on after the photo input goes low. Both inputs have
internal pull-down transistors so that float is logic zero and
connection to VDD is logic 1.
PHOTO Input (Pin 3)
The photo input has hysteresis for a positive trip point. The input will
work with a Light Dependent Resistor (LDR) or a photo-transistor
connected between the input and VDD. The photo device has low
impedance in the presence of ambient light and high impedance in
the presence of ambient darkness.
The IC is configured so that the detection of a light condition must
remain for 6.0 seconds (± 0.5 seconds) continuously in order to be
recognized as a valid light condition. A dark condition must
remain for 1.0 second (± 0.25 seconds) continuously in order to be
recognized as a valid dark condition.
RELAY Output (Pin 1)
This output is configured to drive the base of an external NPN
transistor (see Figure 2). A valid dark condition at the PHOTO input
causes the RELAY output to switch high and a valid light condition at
the PHOTO input causes the output to switch low.
7217-091814-1