EPC111 EPC [Espros Photonics corp], EPC111 Datasheet - Page 6

• Manufacturer Part Number: EPC111
• Description: Fully integrated standalone light barrier driver & receiver
• Manufacturer: EPC [Espros Photonics corp]

Working principle of the digital filter e.g. for the signal OUTN
The aim of this programmable filter is to suppress single pulses, so they cannot trigger the output and generate a false signal.
This filter is based on a counter, which is counting up (increment) the valid pulses and counting down (decrement) the missing pulses in a
weighted manner. There are separate weighting factors for valid pulses (parameter n
reaches the upper limit (maximum count, response time), the signal OUTN is set to LOW. Similar in the opposite direction, if the counter
reaches zero, the lower limit (minimum count, release time), the signal OUTN is put to HIGH. With the parameters n
advantage of individual selectable gradients of the slopes. Counter will never exceed maximum nor minimum limit. In between it acts as an
integrator of both parameters.
IF Pulse then
ELSE wait for Pulse
Lets assume that the photodiode does not receive light pulses for a long time: This means the light beam is interrupted. Then OUTN is at high
level. If the light beam is not interrupted anymore, the photodiode receives light pulses which are strong enough to trigger the OUTN
threshold and the internal pulse evaluation unit (designated in Figure 3 with 'Pulse evaluation') starts to count the received pulses. If the
number of received pulses reach the set level n
generate a false signal.
The same procedure is used when a beam changes from not interrupted to interrupted. The internal pulse evaluation unit counts the missing
pulses. If the number of missing pulses reaches the level n
The same principle applies to the counter and signal of OUTH.
The counter limit values are different, depending on the device:
Light Pulse Detection Output OUTN
The epc111/112 contains two digital outputs to indicate that a valid signal of light pulses are received by the photodiode. The first output OUTN
is triggered, when the lower threshold is reached by the input signal (see Figure 3). This output is used usually to drive the output of the light
barrier. This is a fully CMOS compatible digital output.
© 2011 ESPROS Photonics Corporation
Characteristics subject to change without notice
–
–
IF Pulse = valid then
IF Pulse = missing then
Counter = Counter + (n
IF counter > 2
IF counter = maximum limit then OUTN = 0
Counter = Counter – (2
IF counter < 0 (minimum limit) then Counter = minimum limit
IF counter = minimum limit then OUTN = 1
15
(maximum limit) then Counter = maximum limit
V
n M
epc112
epc111
Type
* 1024)
)
V
, the output OUTN turns to low level. Thus, single pulses cannot trigger the output and
Pulses n
M
Table 2: Filter coefficients
No. of
, OUTN is turned to high level.
int
8
3
to OUTN Filter:
M
6
missing Pulses n
No. of
8
2
V
) and missing pulses (parameter n
V
Datasheet epc111_112 - V2.2
V
and n
epc111/112
M
M
the filter has the
). If the counter
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INT