H7E@-N@P
Connections
■ Terminal Arrangement
3-VDC external
3-VDC external
power supply
H7EC-N@P
H7ET-NP
power supply
Reset
input
Reset
input
Timer
input
Count
input
Bottom view
Bottom view
28 26
17 15
28 26
17 15
Top view
Top view
COUNTS
COUNTS
omronH7EC
omronH7ET
1
3
1 3
12 14
12 14
■ Connections
Power Supply and Battery Connections
Battery Connections
Backup Circuit for Protection Against Power Failure
3-V battery
H7E@-N@P
H7E@-N@P
3-V
bat-
tery
Backup
circuit
When designing a circuit, keep the power wiring connections shorter than 50
mm. Refer to the connection diagram above for the proper wiring polarity.
Use a diode (D) having a forward voltage as small as possible (0.1 V
max. at IF of 20 μA).
The life expectancy of a battery power supply can be calculated by
the following formula:
Determine the ratio of R1 to R2 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.
t = A/lc
Where,
t: Life expectancy of battery (h)
A: Battery capacity (mAh)
lc: H7E@-N@P current consumption (mA)
To protect the circuit against a momentary power failure, an aluminum
electrolyte capacitor can be used in place of a battery, as shown below:
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)
H7E@-N@P
The battery capacity varies depending on the type of battery used;
oxidized silver, mercury, or lithium battery.
Backup
circuit
Voltage Division of Power Supply Circuit
When necessary, the voltage from the battery may be divided by resistances:
When a capacitor is used, its backup time can be calculated by the
following formula:
t = C (V1 – V2) / Ic
H7E@-N@P
Where,
t: Backup time (s)
C: Capacitance (μF)
V1: Supply voltage before power failure (V)
V2: Minimum operating voltage of H7E@-N@P (V)
Ic: H7E@-N@P current consumption (μA)
When doing so, however, ensure that the following equation balances:
Example:
Backup time by an aluminum electrolytic capacitor of 100 μF. (Mini-
E (V) × R2 / (R1 + R2) = 3 V
mum operating voltage of H7E@-N@P is 2.6 V.)
R
E
t = 100 μF × (3–2.6 V)/20 μA = 100 × 0.40/20 = 2.0 seconds
5 V
12 V
24 V
33 kΩ
4.7 kΩ
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.
R1
R2
2 kΩ
3 kΩ
9.1 kΩ
3 kΩ
Allow a current high enough to flow through R1 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 R2 or C as short as
possible (within 50 mm).
Keep the wiring between the H7E@-N@P and R2 or C as short as
possible (within 50 mm).
24
OMRON [ OMRON ELECTRONICS LLC ]
