This circuit was found in a Texas Instruments documentation from the 1980s. The circuit monitors engine temperature by warning of engine warm-up and warning when the fan is on.
This circuit was found in an EDN from the 90s. The circuit employs a double 555 and uses the...
This circuit was obtained from a 1977 magazine, but can still be mounted using BC548 for TR1 and...
This indicator makes use of an LM339 voltage comparator circuit that contains 4 internal...