Battery Connections - Omron H7E Manual

Connections
■ Terminal Arrangement
3-VDC external
H7EC-N@P
power supply
Reset
input
■ Connections
Power Supply and Battery Connections

Battery Connections

3-V battery
H7E@-N@P
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 : H7E@-N@P current consumption (mA)
c
Example:
Battery life when using a 3-V lithium battery with a capacity of
1,200 mAh for the H7E@-N@P.
-3
t = 1,200 [mAh]/20 10 [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:
H7E@-N@P
When doing so, however, ensure that the following equation bal-
ances:
E (V) R / (R + R ) = 3 V
2 1 2
R
5 V
R 2 k
1
R 3 k
2
Allow a current high enough to flow through R
N@P receives sufficient current.
Count
input
E
12 V 24 V
9.1 k 33 k
3 k 4.7 k
so that the H7E@-
1
3-VDC external
H7ET-NP
power supply
Reset
input
C is a film capacitor, of about 0.1 F, and is intended to absorb noise
induced by the power lines.
Keep the wiring between the H7E@-N@P and R
possible (within 50 mm).
Backup Circuit for Protection Against Power
Failure
H7E@-N@P
Use a diode (D) having a forward voltage as small as possible (0.1 V
max. at I of 20 A).
F
Determine the ratio of R
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:
H7E@-N@P
When a capacitor is used, its backup time can be calculated by the
following formula:
t = C (V - V ) / I
1 2 c
Where,
t: Backup time (s)
C: Capacitance ( F)
V : Supply voltage before power failure (V)
1
V : Minimum operating voltage of H7E@-N@P (V)
2
I : H7E@-N@P current consumption ( A)
c
Example:
Backup time by an aluminum electrolytic capacitor of 100 F. (Mini-
mum operating voltage of H7E@-N@P is 2.6 V.)
t = 100 F (3-2.6 V)/20 A = 100
PCB-mounting Counters
Timer
input
or C as short as
2
3-V
bat-
Backup
tery
circuit
to R in accordance with the forward volt-
1 2
Backup
circuit
0.40/20 = 2.0 seconds
H7E@
-N@P C-33