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

[GtwoG PublicOhOne]

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:
> Only last night I got the keypad running again, and was trying to
> insultate the wires to improve its uptime.
>
> So I coated two connections between the rasberry pi and the relay
> which is attached to the door. After coating, it seemed like I somehow
> failed these connections, because the software exited normally
> (opendoor.py was still being called and sent success messages), but
> the door was not opening. I tried to unglue them, but when i was
> taking off the glue, I disconnected one of the wires that was at this
> 3-way junction. Then I resoldered the wires but to no avail.
>
> So everything is totally broken now. Can you help with a multimeter
> and a solder gun Monday to hunt this down? I don't know how to test if
> there is current at point, nor why the two wires would split coming of
> the rpi, and then both go to same relay. BTW what's a relay (i've only
> heard the term)?
>
> Please tutor me in the ways of righteousness,
> notconfusing
> 7074787023
>
>
> _______________________________________________
> sudo-discuss mailing list
> sudo-discuss at lists.sudoroom.org
> http://lists.sudoroom.org/listinfo/sudo-discuss

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