What is the point of reviewing a cheap timer module, especially if it is based on the ubiquitous 555 timer chip? Recently I got an ‘updated’ version of the common 555 timer relay module. This time it ...

This light activated relay circuit presented here uses the 555 timer IC and a light dependent resistor or LDR to form a light sensitive relay in an intruder alarm system or for switching on a lamp at ...

A timer-controlled doorbell device has been developed using two 555 timer ICs in monostable mode, combined with a relay ...

His method relies on a variable-frequency drive (VFD) with programmable IO pins. A simple 555 timer board drives a relay to toggle the IO pins on and off, ...

The linked 555 article makes sense if you read it, but a normal NPN circuit to drive the relay only takes 1mA… easy for most uC’s. Then it starts talking about active low input, and how CMOS ...