LSI/CSI

FEATURES:

• Input interface to a LDR or a photo transistor

• Programmable Duration Selection

• Shunt regulator

• 50Hz / 60Hz time base selection

• Relay Driver output

• LS7217 (DIP), LS7217-S (SOIC) – See Figure 1

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.

the IC. The internal voltage regulator produces 6.0V

± 0.75V.

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

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.

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

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.

 

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747 (631)271-0400

FAX (631) 271-0405

LS7217

Sep2014

FIGURE 1

PIN ASSIGNMENT

7217-091814-1

                           

PHOTO CONTROLLED OUTDOOR LIGHTING WITH PROGRAMMABLE TIMER