DS

Because I’m old school, I wanted to build a Garage Door Closing circuit without relying on integrated configurations (555 timer etc) to keep it simplistic. The circuit closes the garage door after two minutes with C3 and four minutes with the addition of C2. The timer relay is surprisingly accurate (+/- five seconds). Another feature is to ensure that the garage door actually did close, such as if it’s stopped mid-operation by the user. Description: S3 (magnetic N.C.) is located at the garage door and activates the circuit when the garage door opens. RL1 is the reset timer. It’s maintained in the “on” position for two minutes by C3 while the trigger capacitor, C4, is charged. RL2 is the conduit, directing C4 to either RL3 or R1 to ground when off. Purpose of R1 is to prevent arching across contacts and a fast discharge. RL3’s contacts are connected to the Garage Door’s Momentary Switch and is sustained “on”  for a half second by C5. When C3 discharges to the cutoff voltage of RL1, ...

Some relays are constructed with a kind of “shock absorber” mechanism attached to the armature which prevents immediate, full motion when the coil is either energized or de-energized. This addition gives the relay the property of time-delay actuation. Time-delay relays can be constructed to delay armature motion on coil energization, de-energization, or both. Time-delay relay contacts must be specified not only as either normally-open or normally-closed, but whether the delay operates in the direction of closing or in the direction of opening. The following is a description of the four basic types of time-delay relay contacts. First we have the normally-open, timed-closed (NOTC) contact. This type of contact is normally open when the coil is unpowered (de-energized). The contact is closed by the application of power to the relay coil, but only after the coil has been continuously powered for the specified amount of time. In other words, the direction of the contact’s motion (eithe...