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DigiPyro Family - PYD 1998, 1988, 1978 w w w . o p t o e l e c t r o n i c s . p e r k i n e l m e r . c o m


Introduction
All motion detection applications are
employing pyroelectric infrared detectors.
Most units have traditionally been
designed around dual element
configurations. Pyroelectric detectors are
AC-type devices and give signals upon a
change of received infrared (IR) radiation.
Until today, all available detectors were
analog, i.e. they provide an analog signal
output. PerkinElmer now introduces the
first detector series that, unlike previous
generations, offers a digital signal output.


Features and Benefits

Digital output sensor

15-bit output Direct Link

3-pin TO-5 housing

Dual element design

2 x 1 mm² elements

1 mm spacing

Infrared window

5.5...14 µm transmission

Window size: PYD 1998 5.2 x 4.2 mm²

PYD 1988 4,6 x 3,4 mm²
PYD 1978 4,0 x 3,0 mm²

High-level electrical performance

Low EMI sensitivity

Unique responsivity



Applications

Intrusion alarm applications

Motion-activated light switches

Door openers


Authors

Hartmut Jesch,
Gerhard Knaup,
Thomas Kastner
Harald Thomas

PerkinElmer Optoelectronics
Wenzel-Jaksch-Str. 31
65199 Wiesbaden, Germany

Phone: +49 611 492 247
Fax: +49 611 492 170

Email:
Opto.Europe@perkinelmer.com




DigiPyro
®
Family
PYD 1998, PYD 1988, PYD 1978


How to use Dual Element DigiPyro
®

Basics Application Advantages


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Table of Contents
1
Definitions.................................................................................... 3
2
Electrical Configuration .............................................................. 3
2.1

From Analog to Digital .......................................................................................... 3

2.2

The Digital Zero Signal Line.................................................................................. 3

2.3

Out of Range Feature ........................................................................................... 4

2.4

Data Communication ............................................................................................ 4

2.5

Interrupt Driven Read Out..................................................................................... 5

2.6

Electrical Data....................................................................................................... 7

2.7

Typical Responsivity vs. Frequency...................................................................... 8

3
Software Filter Recommendation .............................................. 8
4
Typical Application Circuit ......................................................... 9
5
Operating and Handling.............................................................. 9
5.1

Handling................................................................................................................ 9

5.2

Soldering Conditions............................................................................................. 9

5.3

Product Safety & RoHS ...................................................................................... 10

5.4

Performance Advice............................................................................................ 10

6
Frequently Asked Questions.................................................... 11

List of Figures
Figure 1

Block diagram of DigiPyro
®
................................................................................... 3

Figure 2

DigiPyro
®
connections .......................................................................................... 4

Figure 3

ADC and data transmission diagram (transmitted value: 146 D
Hex
= 5299
Dez
)...... 4

Figure 4

DigiPyro
®
read-out flow chart................................................................................ 5

Figure 5

Frequency response ............................................................................................. 8

Fig.6

Typical application circuit ...................................................................................... 9


List of Tables
Table 1

DigiPyro
®
electrical data ....................................................................................... 7


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P Y D 1 9 9 8 , P Y D 1 9 8 8 , P Y D 1 9 7 8 3
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1
Definitions

Element: This is a sensing surface with a defined size. As all units work with optics, this element and the
optics will determine the performance.
Channel: This refers to an individual detector. When there are two channels, there are also two individual
detectors or two individual outputs.
Detector / Sensor: A detector gives a pure output signal; the sensor has a processed signal output.
Direct link
interface:

The direct link is the interface between DigiPyro® and any micro controller. It is a
bidirectional single wire connection specially designed for this application.
Data Rate: The refresh time of data (availability of new data block).
Resolution: The analog value of one bit.
Clock Time: This refers to the n x (1 / internal clock frequency (the frequency of internal command
processing)).


2
Electrical Configuration

The DigiPyro
®
consists of a dual element configuration that is connected to a special integrated
circuit. It contains the analog-to-digital converter that generates a 15-bit serial signal, a second-order
digital low-pass filter, an on-chip low-power oscillator, and a serial interface. The functional block
diagram is shown below.



Figure 1 Block diagram of DigiPyro
®



2.1 From Analog to Digital

The DigiPyro
®
is the first Pyroelectric detector to display information in bit as compared to mV
signals of analog detectors. For engineers traditionally laying out systems in respect to analog
signals, the following rough comparison may be helpful:

Resolution:
1 bit
6.5 µV

Range:
0 to 16383 bit
± 53.6 mV

DC offset
8250 bit
53.6 mV typical

Noise:
3 bit
19.5 µV (with band-pass)

2.2 The Digital Zero Signal Line

Since the pyroelectric effect generates positive and negative signal amplitudes, the detector circuitry
needs an electrical offset to process the signals. The internal voltage reference provides this offset.
To the user, this offset appears as a digital zero line ranging at 8250 bit and may differ in series from
one part to the next. To recognize the zero line of the individual detector, the user may use either a
VDD

VSS
direct link
Voltage
reference
Oscillator
A/ D
Conversion
Decimator
10Hz LP
Serial
Interface
Pyro
Elemen
ts
direct link

communication
(Single line
bi-directional
interface
)
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P Y D 1 9 9 8 , P Y D 1 9 8 8 , P Y D 1 9 7 8 4
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digital band-pass or subtract the measured offset from the signal. To do so, the detector must be
covered from incidental radiation and protected from possible air drafts and indirect radiations. The
detector output is then monitored. The resulting signal represents the individual zero line. Once the
reading is stabilized, this value can be taken and stored in the users µProcessor as the detectors
zero line. The same feature is provided by PerkinElmers application kit for the DigiPyro
®
.

2.3 Out of Range Feature

To avoid detector saturation, the DigiPyro
®
includes a special out-of-range detection feature. It shows
when the detector runs into saturation caused by temperature shock, which can result from touching
the detector with warm hands. This special feature of the digital detectors shortens the input of the
circuit for a duration of 512 system clocks as it monitors the digital values rising above 15872 bit or
falling below 511 bit. If this re-occurs, the input is shortened repeatedly until the thermal shock
problem has expired.

2.4 Data Communication


Figure 2 DigiPyro
®
connections
The serial interface has a 15-bit binary output format that allows a physical data value range from 0 to
32767. However, due to the ADC resolution of 14 bit, the most significant bit (MSB) is always LOW and,
thus, the data range is limited to values from 0 to 16383. The direct link pin is used as bi-directional
data output and clock input.

The following diagram shows the communication signal flow:


Figure 3 ADC and data transmission diagram (transmitted value: 146 D
Hex
= 5299
Dez
)
A data block transmission cycle (refresh