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PRECAUTIONS IN USING THE LT4H SERIES
Once the wiring to be used is completely
installed and prior to installing this timer,
confirm that there is complete insulation
between the wires connected to the
power terminals (2 each) and the wires
connected to each input terminal. If the
power and input lines are not insulated, a
short-circuit may occur inside the timer
and result in internal damage.
In addition, when moving your equipment
to a new installation location, confirm
that there is no difference in environmen-
tal conditions as compared to the previ-
ous location.
( Fig. A ) Good example
AC power supply
Insulation transformer
(+)
(–)
(–)
Timer
( Fig. B ) Bad example
AC power supply
Insulation transformer
(+)
(–)
(–)
Timer
AC power supply
Single coil transformer
(+)
(–)
(–)
Alternative
Timer
current flow
4) The input signal is applied by the
shorting of each input terminal with the
common terminal (terminal Q for 8-pin
types, terminal E for 11-pin types and
terminal
for screw terminal types).
6
Never connect other terminals or volt-
ages higher than 40V DC, because it
may destroy the internal circuitry.
5) Transistor output
(1) Since the transistor output is insulat-
ed from the internal circuitry by a pho-
tocoupler, it can be used as an NPN
output or PNP (equal value) output.
(The above example is 11-pin type)
LT4H timer
As NPN output
{
O
Load
Load's power supply
LT4H timer
As PNP output
{
O
Load
Load's power supply
Note: With the 8-pin type, there is no diode
between points I and O.
48
(2) Use the diode connected to the out-
put transistor's collector for absorbing
the reverse voltage from induced loads.
Diode rating:
I
(forward current): 1 A
F
V
(reverse voltage): 600 V
R
6) When wiring, use shielded wires or
metallic wire tubes, and keep the wire
lengths as short as possible.
7) For the load of the controlled output,
make sure that it is lower than the rated
control capacity.
Input device
( e.g. , sensor )
4. Operation of LT4H digital timer
1) Turning on and off the power supply
while operating in A2* (Power on delay
2) or G (Totalizing On delay) will result in
a timer error to be generated due to the
characteristics of the internal circuitry.
Therefore, use the start input or stop
Input device
( e.g. , sensor )
input.
* Not related to the start input.
2) When controlling the timer by turning
on the power supply, use only A (Power
on delay 1) or A2 (Power on delay 2).
Use of other modes in this situation will
Input device
( e.g. , sensor )
result in timer errors. When using the
other modes, control the timer with the
start input or stop input.
5. Operation mode and time range set-
ting
The operation mode and time range can
be set with the DIP switches on the side
of the timer. Make the DIP switch set-
tings before installing the timer on the
panel.
The operation mode of LT4H-W series
can be set with the keys and switches on
the front of the timer.
6. Conditions of usage
1) Avoid locations subject to flammable
or corrosive gases, excessive dust, oil,
vibrations, or excessive shocks.
2) Since the cover of the timer is made of
polycarbonate resin, avoid contact with
or use in environments containing methyl
alcohol, benzene, thinners, and other
organic solvents; and ammonia, caustic
I
sodas, and other alkaline substances.
3) If power supply surges exceed the val-
ues given below, the internal circuits may
become damaged. Be sure to use surge
absorbing element to prevent this from
happening.
Operating voltage Surge voltage (peak value)
I
AC type
DC type
24V AC type
LT4H timer
Inductive load
Load's
power supply
6,000V
1,000V
• Surge wave form
[± (1.2 × 50) µs uni-polar full wave voltage]
100
90
Peak
50
30
0
0
1.2
Time (µs)
4) Regarding external noise, the values
below are considered the noise-resistant
voltages. If voltages rise above these
values, malfunctions or damage to the
internal circuitry may result, so take the
necessary precautions.
Power supply terminals
DC type
AC type
24V AC type
Noise
1,500V
1,000V
voltage
Noise wave form (noise simulator)
Rise time: 1 ns
Pulse width: 1 µs, 50 ns
Polarity: ±
Cycle: 100 cycles/second
5) When connecting the operating power
supply, make sure that no leakage cur-
rent enters the timer. For example, when
performing contact protection, if set up
like that of fig. A, leaking current will
pass through C and R, enter the unit,
and cause incorrect operation. The fig. B
shows the correct setup.
Leakage current
Operating power supply
R
(Fig. A)
Operating power supply
(Fig. B)
50
Input
terminals
600V
T
C
R
T
C
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