Re: [sudo-discuss] Door and Keypad Update and Need Help (Electronics Knowledge)

Hi Max- (to list) A relay is essentially an electromagnet that operates a set of switch contacts. Think of the electromagnet as similar to a spool of thread with a dowel running through the center. The thread is fine wire. The dowel is made of ferrous metal. At one end of the dowel, is part of an armature that is pivoted to act as a lever. The other end of the lever is insulated in some way, and acts upon the set of switch contacts. When power is applied to the electromagnet, it attracts the nearby part of the armature, exerting leverage to operate the switch contacts. Relays are typically used for switching of signal paths (telephone switching) and for switching of unlike power (power relays). The physical construction of relays varies widely, from small ones mounted on circuit boards, to large ones mounted on racks. In the door opener, the relay may be designed to take logic-level power (5 volts DC) and operate a set of switching contacts that handle a higher level of power from the door strike power supply to the door strike itself (typically 24 volts AC or DC). This is probably a small relay, an inch by a half-inch or so, but relays can get quite large depending on their application. If you want to see more relays in one place than you're ever going to see in real life, keyword search "strowger switch", preferably on a video site so you get to see them operating. -G. ===== On 13-11-24-Sun 8:17 PM, Max Klein wrote: