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Door switch activated chime? #169323 10/01/07 09:46 PM
Joined: Oct 2007
Posts: 56
SP4RX Offline OP
Hey everyone! I've been lurking here for a long time and I can say I've definitely learned a lot from your collective experience. I have a situation that I can't seem to figure out, so I thought I might pick your brains a little.
Here's the deal: a customer, whose new building I'm doing the wiring in, has requested a chime kit by the front door so that the occupants will be notified if someone enters the building. Pretty simple I think, and during rough-in pull a #18 2-wire cable to the door frame for a door switch. The cable now comes out of the drywall along the interior surface of the door frame. Now that I'm doing the final work, I'm not sure what kind of switch I should use. I thought I would use a security type n.o. reed switch, but the contacts would be closed the whole time the door was open and I'm not sure that having the chime coil energized for that long would be good for it.
Do any of you know of a switch I can use - surface mounted, n.o. contacts which momentarily close when the door opens, but don't need the door to close again for the contacts to open?
There has to be a way I can do this but I can't figure it out.
Many thanks to anyone who can help me out here, and many more thanks to everyone else for all the other stuff I've learned here also.


Work Gear for Electricians and the Trades
Re: Door switch activated chime? [Re: SP4RX] #169325 10/01/07 10:09 PM
Joined: Jul 2007
Posts: 265
wire_twister Offline
i dont know of a switch, but you could use a time delay relay, it would pull in when door opens, sounding the chime and stay pulled in for a set time then drop out which would de-energize the chime. Whole sequence resets when the door is reclosed.


Life is tough, Life is tougher when you are stupid
Re: Door switch activated chime? [Re: wire_twister] #169326 10/01/07 10:19 PM
Joined: Jul 2004
Posts: 9,568
gfretwell Offline
SPDT switch and a capacitor? Charge the cap when the door is closed and discharge the cap across the chime when the door opens. Run it from a small DC wall wart.

Greg Fretwell
Re: Door switch activated chime? [Re: gfretwell] #169328 10/01/07 10:32 PM
Joined: Mar 2004
Posts: 251
Use a ATW PC300 You need a NO contact at the door and a power supply 12VDC This unit has a choice of several tones, and can be program to chime only one, two or three times regardless of how long the door is open.

Re: Door switch activated chime? [Re: WESTUPLACE] #169331 10/01/07 11:39 PM
Joined: Oct 2007
Posts: 56
SP4RX Offline OP
Wow, you guys are quick! And ingenious too, I never would have thought about using a capacitor to operate a chime. I'm not sure how i would size the cap. though. I got to considering relays but time delays won't close on energization and then close a few tenths of a second later. While looking up relays online I came across some info for "one-shot" relays. "One-shot timers provide a single contact pulse of specified duration for each coil energization (transition from coil off to coil on)" Sounds like one of these would work, just need to find out what voltages these come in...and prices too. Hopefully this will work, but for some reason I would like to use a capacitor. It sound so much cooler and would probably impress my boss. smile
Thanks for the speedy replies and I hope to get a few more ideas.
This site rocks


Re: Door switch activated chime? [Re: SP4RX] #169335 10/02/07 07:02 AM
Joined: Dec 2001
Posts: 2,491
Texas_Ranger Offline
Hm... there should be switches that are open when pressed and close upon being released. This sounds like a good idea here. Different idea: inverse relay. Need one for permanently excited coils though.

Re: Door switch activated chime? [Re: Texas_Ranger] #169337 10/02/07 09:31 AM
Joined: Oct 2006
Posts: 745
EV607797 Offline
Edwards makes a trip switch that literally hangs in the path of the door swing. Once the door hits it, it makes a momentary contact. It's designed to NOT make contact again when the door closes. Most supply houses carry the Edwards brand, but if your's doesn't, try an electronics specialty store. Edwards' part number for this is #236 and it appears that Rexel carries this brand.


"But the guy at Home Depot said it would work."
Re: Door switch activated chime? [Re: EV607797] #169339 10/02/07 10:58 AM
Joined: Jul 2004
Posts: 9,568
gfretwell Offline
If you use an electronic chime the current draw is minimal so you wouldn't need that big a capacitor to hit it but if you really want to make some noise, use a relay or SSR to buffer the shot.

Greg Fretwell
Re: Door switch activated chime? [Re: gfretwell] #169396 10/03/07 07:29 PM
Joined: Jul 2002
Posts: 8,379
Trumpy Offline
Hi Shawn,
You mentioned in your first post that the door could be left open, a mechanical door closer wouldn't be a silly idea, if not from a security point of view, to stop people from wandering in.

Re: Door switch activated chime? [Re: Trumpy] #169419 10/04/07 05:50 PM
Joined: Jan 2005
Posts: 109
Grover Offline
I had a similar problem in my old house. People around here just walk in to the shed and tap on the door into the kitchen. Solved with X-10, and a magnetic switch. Chime module in my office, upstairs in the back. No fancy controller, just the mag switch module and the chime module. No extra wires either!

Never failed.......


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