This circuit activates a relay after a time given by C1 and R1. The circuit is from a Radio Electronics from December 1974. The relay voltage is the same as that used in the power supply.
With this circuit it is possible to keep the current in an LED constant even if the supply voltage...
April 2017 - TDK chip-on-ceramic components can be obtained from Mouser Electronics for 2.4 GHz...
The transistors T1 and T2 of this circuit can be the BC558. T3 can be a BD135 and T4 a TIP42. The...