Hardware Reference
In-Depth Information
Figure 9.33
Typical medium- and high-current driver circuits: (a) transistor
low-current relay driver; (b) Darlington medium/high-current relay driver; (c)
MOSFET relay driver; (d) Darlington filament lamp driver
Figure 9.34
An LED indicator can be easily added to a relay driver
Finally, where visual indication of the state of a relay is desirable it is a simple
matter to add an LED indicator to the driver stage, as shown in Figure 9.34.
Audible outputs
Where simple audible warnings are required, miniature piezo-electric trans-
ducers may be used. Such devices operate at low voltages (typically in the range
