Boosting Relay Drive Current
4-5
Boosting Relay Drive Current
PIO-SSR Series boards can drive relays other than the standard solid-state
relays. The maximum output current for each channel of a PIO-SSR
Series board is 24mA at 5V. If your relay requires more than 24mA or
more than 5V, you can boost the drive current and/or voltage for relay
control using the circuit shown in Figure 4-7.
Figure 4-7. NPN Transistor Relay Control for an Output of a
PIO-SSR Series Board
For drive-current requirements between 15mA and 100mA, select an
NPN transistor with appropriate current capacity. The power transistor
must be rated for the required supply voltage and must have a collector
current rating no higher than 0.5A. If higher current is needed, substitute a
Darlington NPN transistor.
PIO-SSR Series
Board
470
Ω
Min.
Digital
Output
#
n
NPN
Transistor
Surge
Protection
Diode
Digital
Common
GND
To Relay
DC Power
Supply
+
−
Relay
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