This circuit is from a 1978 Texas Instruments optoelectronics manual. The trimpot adjusts the LED current. Other currents can be adjusted if they are within the capacity of the FET.
This configuration (using a logic gate with TTL compatible output) uses an amplifier transistor to obtain...
In addition to the didactic purpose, the figure circuit can also be automated. In this case, the...
The maximum time interval of this circuit depends on C1. Larger values can be used to get closer to...