epc120

In more detail, such a sequential operation is typically like as follows:

1.

The first epc120 element is turned on (active mode).

2.

On a second command this element sends a short light pulse towards his reflector or object, forming the active light beam

➊.

3.

If there is no obstacle between epc120 and his reflector, the element receives this light pulse and stores it into a local memory.

4.

The bus controller reads out the content of the memory in the epc120 chip and stores the status (light beam interrupted or not

interrupted) into its data memory.

5.

Finally, epc120 is turned off (standby mode).

This sequence, which is also called 'scan', is repeated until all beams are checked and their status is stored in the beam status memory of the

bus controller.

The above mentioned sequence is repeated until power is switched off. Because of the fact, that an object can enter into a light beam right

after a beam has been checked with the above mentioned procedure, up to two full scan sequences are necessary to reliably detect an

object. Thus, the overall maximum response time of the system will be

t

(1)

where

= response time of the system

n

= number of elements or light beams

= time to evaluate the beam status memory and generate the output signal

For further reference in optical design considerations please refer to the respective application notes available from epc.

Figure 5 shows the epc120 in a distributed light barrier system application. The epc100 acts as a bus controller.

µC

GND

VDD µC

VDD

R

LED

+ I

LED

- I

LED

Element 1

R

LED

Element 2

VDD

PD

VDD33

epc120

GND

LED

R

LED

Element n

VDD

PD

epc120

GND

LED

VDD33

VDD

VDD33

epc100

GND

SO

SCK

SI

CS

VDD

PD

VDD33

epc120

GND

LED

Figure 5: epc120 in the light barrier application as receivers and the interface chip to the microcontroller

From the point of view of the microcontroller, the whole system looks like a single device with several addressable sensors: the microcontroller

activates one epc120 element and fetches the results after a predefined time.

LED and is not needed in non-safety applications. If such a resistor is inserted, a failure mode can be detected, if more than one LED is active

due to a short circuit or a failure in the epc100. It is also possible to have a common voltage supply and to generate the LED current by a

resistor.

© 2011 ESPROS Photonics Corporation

Characteristics subject to change without notice

7

Datasheet epc12x - V2.1

www.espros.ch