ic-wt iC-Haus, ic-wt Datasheet - Page 6

• Manufacturer Part Number: ic-wt
• Description: Incremental Encoder
• Manufacturer: iC-Haus

Figure 1 illustrates the layout of the entire electronic system of an incremental rotary encoder. The devices
iC-OR (photodiodes array), iC-WT (incremental encoder) and iC-WE (line driver) from iC-Haus are used.
The rotary encoder requires the supply voltages VCC= +5V and VB= +5V to +30V (line driver) and supplies the
conditioned signals of tracks A and B and index track Z at the outputs. It’s possible to transmit these signals
over directly connected lines of 100m length. The system’s upper cut-off frequency is 500kHz for track A/B.
Internal monitoring functions are available for the chip temperature of the line driver, for the supply voltages and
for the LED current control. The ERROR port provides an error message signal which can be logically linked
to other, external error signals by simple connection.
Fig. 1: Incremental rotary encoder
DESCRIPTION OF FUNCTIONS
The photodiodes array iC-OR comprises two diodes each for tracks A and B (differential evaluation) and one
diode for track Z (index pulse for constant-light evaluation) in the layout typical for an incremental encoder. A
reference diode is not required since the threshold for the index signal is generated from the signals of tracks
A and B. It is also possible to use the iC-Haus device iC-WS or the Siemens device KOM 2100.
The incremental encoder iC-WT evaluates the currents of the photodiodes and generates TTL-compatible
information. The zero pulse is logically linked to the tracks A and B with an AND operation. This operation can
be cancelled for adjustment purposes by applying a low level to the error message output NERR (combined
input and output).
An integrated transmit-current drive circuit makes the adjustment to a constant summation photoelectric current
at inputs A/B which is specified as the reference current at ILR by means of the external resistor RLR. The
external capacitor CLR stabilizes this adjustment. Using a further reference current at IZ which is set with RZ
it is possible to specify the constant-light evaluation threshold for the zero pulse at a controlled and,
consequently, constant illuminance. With identical geometries and homogeneous illumination of all photodiodes,
ILR and IZ can operate on a common resistor.
The resistor RLED limits the maximum possible current through the LED. The transmit-current control features
an error detector which sets the output NERR to LOW (open collector) when the permissible working area is
exited. The error message detector is activated, for example, in case of a defect of the LED, when the code
discs are dirty or steamed, or in the case of excessive influence of lights from an external source.
iC-WT
INCREMENTAL ENCODER
APPLICATIONS INFORMATION
Rev A0, Page 6/13