Found in a 1980s publication, this circuit can be modified to use modern components and operate at lower voltages. The power supply does not have to be symmetrical.
This simple timer is from a 1998 publication. Other operational amplifiers can be used, and the...
In fact, it is a RF field indicator with an operational amplifier equivalent to the 741. This...
Relays specially designed for operation in harsh environments of Phoenix Contact can be purchased...