E6580772
③
18
★
Caution in case of using open collector encoder connection
In case using pulse command oscillator and open collector encoder, the rise time of the voltage when the
transistor is OFF tends to be longer than the fall time at the time when the transistor is ON. Therefore, if the
maximum input frequency becomes higher, the pulse duty cannot maintain the 50±10% specification.
Conduct derating on the maximum input frequency so that the pulse duty will be within the following
specification range.
<Derating computation formulae of open collector’s maximum input pulse frequency >
0.8
／
(Maximum input frequency x A) – Voltage rise time
≧
3 x 10
–6
…..
①
A : (single phase input: 2) (two-phase input: 4)
Voltage rise time
＝
Encoder exclusive pulse rise time + R x C
Encoder exclusive pulse rise time (s) : Please inquire at the encoder manufacturer.
R (
Ω
) (Input resistance)
: internal resistance 1000(
Ω
)
＋
external resistance value
(In case there is external resistance)
C(F) (Cable static capacity)
: Please inquire at the cable manufacturer.
<Example>
Encoder
: LBJ-005-500 (SUMTAK), 2-phase input
Encoder pulse rise time : 0.35 x 10
-6
(s)
Cable
: ROVV-SB-0.2-5P-10m (Furukawa Electric Co., Ltd)
Static capacity : 120 x 10
–12
(F/m) x 10 (m)
From Formulae
①
0.8
／
(Maximum input frequency x A) – Voltage rise time
≧
3 x 10
–6
Voltage rise time = (0.35 x 10
–6
) + 1000 x (120 x 10
-12
x 10)
= 1.55 x 10
-6
[Maximum input frequency]
≦
87912 (Pulse/s) [Single phase input]
≦
43956 (Pulse/s) [Two-phase input]
3.2.3 Selection of encoder type
The encoder type should be selected, following the table below.
Encoder Type
Characteristics
Maximum Wiring Length
Complementary
Rated voltage output with emitter/follower
combination.
High anti-nose characteristics. High-speed response.
Long-distance transmission capability.
Need to pay attention to waveform irregularity.
１００ｍ
Open Collector
The collector of the transistor is output directly.
Low anti-noise characteristics. Low-cost.
Need to pay attention to waveform irregularity and
distortion.
１０ｍ
