The presented circuit uses a PNP transistor, which can be the BC558. Observe the polarity of the supply. The circuit is suggested by Texas Instruments opto-electronic documentation.
We found this circuit in the April 1988 issue of Radio Electronics magazine. The circuit can be...
Relays up to 100 mA can be driven by the 555 with the recommended circuit. The circuit is from an...
This version of the previous circuit, also from Radio Electronics magazine of July 1970, uses R4...