epc100

Application Information

Schematic Circuit of one Node

Figure 5 shows the schematic circuit of one node on a light curtain system. A node consists of four components only: The receiver chip ep-

c100, a photo diode and two supply voltage decoupling capacitors.

Recommended Components Values

PD: PIN photo diode, i.e., epc300, epc310, epc320, epc330 (refer to the separate available data sheet epc3xx), or similar

C1: 100nF ceramic capacitor

C2: 4.7nF ceramic capacitor

Design Precautions

The sensitivity at pin PD is very high in order to achieve a long operation range of light curtains even without lenses in

front of the IR LED and/or the photo diode. Thus, the pin PD is very sensitive to EMI. Special care should be taken to

keep the PCB track at pin PD to the photo diode as short as possible (a few mm only!). This track should be kept

away from sources emitting electromagnetic noise which may induce unwanted signals. It is strongly recommended to

cover the chip and the photodiode with a metal shield. A recommended part is shown in Figure 6.

The pins at the bottom are to solder the shield to the PCB with electrical connection to GND. The hole in the front is

the opening window for the photo diode. The back side of the PCB below the sensitive area (PD, epc100) shall be a

polygon connected to GND to shield the circuit from the back side. The capacitors shall be of high mechanical stability

(no piezoelectric effect) in order to avoid unwanted voltage modulation by mechanical shock or vibration.

Ambient Light

is above the stated value, the input is saturated which blocks the detection of AC current pulses.

Photodiode Capacitance

If the photodiode capacitance is below the specified value, the system becomes more sensitive to power supply ripple voltage at higher fre -

quencies (>200kHz). This sensitivity can be reduced by a parallel capacitor to the photodiode. However, this measure reduces the detection

sensitivity. If the photo diode capacity is above the specified value, a lower detection sensitivity and a higher sensitivity spread results.

© 2011 ESPROS Photonics Corporation

Characteristics subject to change without notice

6

Datasheet epc100 - V2.1

www.espros.ch

Figure 5: Schematic circuit of one node

PD

VDD33

VDD

epc100

GND

VDD18

C1

C2

PD

2-wire bus: positive terminal

2-wire bus: negative terminal

Figure 6: Recommen-

ded EMC shield