Brochure

32
Technical Information – Relays
Item Symbol Rating
Collector–base voltage V
CBO
60 V
Collector–emitter voltage V
CBO
50 V
Emitter–base voltage V
CBO
5.0 V
Collector current (DC) I
C
(DC) 100 mA
Collector current (pulse) I
C
(pulse)* 200 mA
Base current (DC) I
B
(DC) 20 mA
Base current (pulse) I
B
(pulse)* 40 mA
Total power dissipation P
T
250 mW
Junction temperature T
J
125°C
Storage temperature T
stg
-55°C to 125°C
IPW <_ 10 ms, duty cycle >_ 50%
■
Correct Use
RELAYS IN ELECTRONIC CIRCUITRY
Driving by Transistor
When a transistor is used to drive the relay, be sure to ground the
emitter of the transistor.
When the transistor is used in a emitter-follower configuration
(i.e., the collector is grounded), give adequate consideration to
the voltage across the collector and emitter. The required voltage
must be applied to the relay.
Selecting a Transistor for Driving the Relay
After determining which relay to use, and after becoming familiar
with its ratings, select a transistor to drive the relay.
1. From the relay’s catalog or data sheet, ascertain the following
characteristics:
Rated voltage: _ VDC
Rated current: _ mA
coil resistance: _ Ω
2. Determine the minimum and maximum values of the must
operate voltage form the rated voltage.
Minimum must operate voltage: _ V
Maximum must operate voltage: _ V
(If ripple is contained in the rated voltage, obtain the maximum
value including the ripple.)
3. By determining the component for suppressing surge, obtain
the dielectric strength of the transistor for driving the relay.
* This safety factor must be determined by the user.
** The breakdown voltage differs, depending upon the
component. Therefore, if multiple zener diodes are to be used,
use their maximum breakdown voltage.
*** The varistor voltage differs depending upon the component. In
addition, the varistor voltage of a single varistor may vary
depending upon the current. Consult the manufacturer of the
varistor to be used to determine the varistor voltage.
**** The surge voltage differs depending upon the type and rating
of the relay, and the constants of C and R of the circuit in which
the relay is used. Positively determine the surge voltage by
experiment.
4. Determine collector current I
C
.
I
C
= Maximum must operate voltage/coil resistance x 2*
5 *This safety factor must be determined by the user.
Select the transistor that satisfies the conditions determined in
steps 3 and 4 above.
Absolute Maximum Ratings (NPN Transistor Ratings)
NPN transistor
PNP transistor
< In the case of diode>
(Maximum of must operate voltage + 0.6) x 2*
≅ VCEO ≅
VCBO = __V
< In the case of diode and zener diode>
(Maximum of must operate voltage + 0.6 + breakdown
voltage**) x 2* ≅ VCEO ≅ VCBO = __V
< In the case of varistor>
(Maximum of must operate voltage + varistor voltage***)
x 2*
≅ VCEO ≅ VCBO = __V
< In the case of RC>
(Maximum of must operate voltage + surge voltage****) x
2* ≅ VCEO ≅ VCBO = __V
where,
R
≅ Coil resistance of relay
(measured changing the value of C)
C = 0.01 to 0.2 µF
Surge voltage
Oscilloscope
Power source to relay
Omron A5 Catalogue 2007 1-282 11/9/06 10:16 am Page 32