PCB-mounting Counters H7E@-N@PC-33
Counters
Connections
■ Terminal Arrangement
■ Connections
Power Supply and Battery Connections
Battery Connections
When designing a circuit, keep the power wiring connections shorter
than 50 mm. Refer to the connection diagram above for the proper
wiring polarity.
The life expectancy of a battery power supply can be calculated by
the following formula:
t = A/l
c
Where,
t: Life expectancy of battery (h)
A: Battery capacity (mAh)
l
c
: H7E@-N@P current consumption (mA)
Example:
Battery life when using a 3-V lithium battery with a capacity of
1,200 mAh for the H7E@-N@P.
t = 1,200 [mAh]/20 × 10
-3
[mA] = 60,000 hours (approx. 6.8 years)
The battery capacity varies depending on the type of battery used;
oxidized silver, mercury, or lithium battery.
Voltage Division of Power Supply Circuit
When necessary, the voltage from the battery may be divided by
resistances:
When doing so, however, ensure that the following equation bal-
ances:
E (V) × R
2
/ (R
1
+ R
2
) = 3 V
Allow a current high enough to flow through R
1
so that the H7E@-
N@P receives sufficient current.
C is a film capacitor, of about 0.1 µF, and is intended to absorb noise
induced by the power lines.
Keep the wiring between the H7E@-N@P and R
2
or C as short as
possible (within 50 mm).
Backup Circuit for Protection Against Power
Failure
Use a diode (D) having a forward voltage as small as possible (0.1 V
max. at I
F
of 20 µA).
Determine the ratio of R
1
to R
2
in accordance with the forward volt-
age of the diode to be used. Be aware that when the power supplied
to the H7E@-N@P has dropped to less than the voltage of the
backup circuit, the battery will discharge.
To protect the circuit against a momentary power failure, an alumi-
num electrolyte capacitor can be used in place of a battery, as shown
below:
When a capacitor is used, its backup time can be calculated by the
following formula:
t = C (V
1
- V
2
) / I
c
Where,
t: Backup time (s)
C: Capacitance (µF)
V
1
: Supply voltage before power failure (V)
V
2
: Minimum operating voltage of H7E@-N@P (V)
I
c
:H7E@-N@P current consumption (µA)
Example:
Backup time by an aluminum electrolytic capacitor of 100 µF. ( M i n i -
mum operating voltage of H7E@-N@P is 2.6 V.)
t = 100 µF × (3-2.6 V)/20 µA = 100 × 0.40/20 = 2.0 seconds
H7EC-N
@
P H7ET-NP
3-VDC external
power supply
Reset
input
Count
input
Reset
input
Timer
input
3-VDC external
power supply
RE
5 V 12 V 24 V
R
1
2 kΩ 9.1 kΩ 33 kΩ
R
2
3 kΩ 3 kΩ 4.7 kΩ
3-V battery
H7E
@
-N
@
P
H7E@-N@P
H7E
@
-N
@
P
3-V
bat-
tery
Backup
circuit
H7E@-N@P
Backup
circuit
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