This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
Written in an article in Radio Electronics magazine in April 1987, this circuit triggers an alarm...
This is the receiver circuit for the previous transmitter. The circuit has a programming key to...
This is an example of a temperature sensor shield using the Texas Instruments TMP390 obtained from...