Datasheet

H7E@-N@P
24
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 balances:
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 aluminum
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. (Mini-
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
Note that the above calculation provides an approximate value,
which varies depending on the environment under which the Counter
is used and also on the type of capacitors used. Provide some allow-
ance in selecting capacitors.
Keep the wiring between the H7E@-N@P and R
2
or C as short as
possible (within 50 mm).
13
12 14
28 26 17 15
H7EC-N@P H7ET-NP
3-VDC external
power supply
Reset
input
Count
input
Reset
input
Timer
input
3-VDC external
power supply
Bottom view Bottom view
omronH7EC
COUNTS
13
12 14
28 26 17 15
omronH7ET
COUNTS
Top viewTop view
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