H7E-P
H7E-P
4
Connections
■
H7EC-P, H7EC-PL, H7ET-P
■
H7ER-P, H7ER-VP, H7ER-V2P
Power supply
All H7E
❑
-
❑
P models require a 3 VDC external power source.
When designing a circuit, plan the power wiring connections to
be within 50 mm (1.97 in). Refer to the connection diagrams
above for proper wiring polarity.
The life expectancy of a battery power source can be calcu-
lated by the following formula:
t = 1000 A/lc
where,
t: life expectancy of battery (h)
A: battery capacity (mAh)
lc: current consumed by H7E
❑
-
❑
P (
µ
A)
Voltage division of power source circuit
When necessary, the voltage from the battery may be divided
by resistances:
When doing so, however, ensure that the following equation
balances:
E (V) x R
2
/ (R
1
+ R
2
) = 3V
Allow a current high enough to flow through R
1
so that the
H7E
❑
-
❑
P receives adequate current.
C is a film capacitor, of about 0.1
µ
F, and is intended to absorb
noise superposed from the power lines.
Keep wiring between the H7E
❑
-
❑
P and R
2
as short as
possible, within 50 mm (1.97 in).
Use a diode (Di) having a forward voltage as small as possible
(0.1 V max. at I
F
of 1 mA). Determine the ratio of R
1
to R
2
in
accordance with the forward voltage of the diode to be used.
Be aware that when the supply voltage of power source E has
dropped to less than the voltage of the backup circuit, the
battery discharges. To protect the circuit against a momentary
power failure, an aluminum electrolyte capacitor can also be
used in place of a battery, as shown below:
When the capacitor is used, its backup time can be calculated
by the following formula*:
t = C(V
1
-V
2
)/lc
where,
t: Backup time (s)
C: Capacitance (
µ
F)
V
1
: Supply voltage before power failure (V)
V
2
: Minimum operating voltage of H7E
❑
-
❑
P (V)
lc: H7E
❑
-
❑
P current consumption (
µ
A)
* In all applications which require the counter to maintain the
accumulated display for a longer time, increase the capaci-
tance to an appropriate value.
Input connection
Contact input
Backup circuit for protection against power failure
