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.
Shawn.
Shawn,
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.
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.
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.
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.
Thanks for the speedy replies and I hope to get a few more ideas.
This site rocks
Shawn.
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.
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.
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.
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.
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.......
Grov
Well, it looks like Ed has given me exactly what I was asking for! This switch would be absolutely perfect for the intended application...but the customer would never allow it on the front door of his business. Close, but no cigar.
I haven't gotten into a wholesaler yet to ask about one-shot relays yet, hopefully tomorrow morning.
Trumpy...what I meant about the door being open was just the amount of time it would take for the door to close itself after being opened. The main reason I don't want to use a n.o. switch in this situation is that there are actually two doors to this business, and two chime kits. The front door is set to chime once when a customer enters (ding), and the back door is set to chime twice (ding-dong). With a n.o. reed switch at the back door the coil would energize when the door opened, sending the plunger into the first chime. (ding) But now the coil remains energized until the door closes and the reed switch contacts open, de-energizing the coil, allowing the plunger to be pulled up by spring pressure and hit the second chime. (dong) The trouble is that when either door opens like this you would only hear the ding sound...and if it's the back door that opened you wouldn't know it until the door were once again completely closed...kinda defeating the purpose of having two chime kits to differentiate which door is being opened.
I wish I'd have thought about this before recommending the idea to the customer! Oh well, hopefully I can find a relay that will give the coil a quick jolt.
Fretwell...there's nothing electronic about these chimes...two coils, each with a spring loaded plunger running through it. energize a coil and force its plunger down into a metal bar. de-energize coil and the spring returns plunger to top...one plunger hits a stop bumper, the other hits a second metal bar. pretty simple stuff.
Thanks again everyone.
Shawn.
Shawn,
First of all, Welcome to ECN! Do you think the customer would accept a "Ding" or "Ding Dong" on opening and closing? If so, consider using two reeds, one NOHC, and one NCHO, in series at two points on the arc radius of the door. The inner NOHC would stay in the magnetic field longer and still be closed for a short time after the NCHO closes. I also remember that different reeds were made for larger gaps for garage doors and the like. But again, it will most likely sound on closing too. The advantage is that 4 reeds are cheaper than 2, "interval on" TDRs and require no cabinet space.
Naturally, you would want the NCHO reed and the shortest "interval on" relay you can get if you go that route.
Joe
The sounder I suggested earlier in this post will produce a Ding/Dong when you close a door mounted switch. By setting the dip switches on the back it will sound continuously or only 3 times upon contact closure no mater how long the door is open. You can get it from any alarm supply co. (ADI) Will mount in a 1 gang box. Just need a normally open mag switch on the door. I have one on my shop door.
Hey Joe, thanks for the warm welcome. Firstly, let me say that your solution is absolutely brilliant. I never would have thought of it. I'm going to put the idea to the customer for consideration, but he's probably not going to go for it. I'm not sure what he'll like less...having the doorbells chiming twice, or having a second switch on his door with a cable running between the two. He's quite fussy. His fussiness is why I can't use the switch that Ed (EV607797) posted earlier...to much of an eyesore no matter how well it works.
Westuplace...thanks for the tip on the different chime unit. I think it's too late to swap out the actual chime. It's been a few days since I was on-site and the painters may be complete now. The old chimes would have to come down, the screw holes would need to be patched and the exposed area painted. I wish I had found out about this model earlier, I probably would have chosen it.
I fell like I'm shooting down all of your great ideas, it's just that this customer wants things just so. If I can't swap out the chimes then I suppose I'll just have to find the right relay and buy two of them along with boxes to mount them in. Oh well, that's the way it goes sometimes. Next time I'll know better!
Thanks again, you guys are awesome, I hope I can return the assistance some day.
Shawn.