Film-Tech Forum ARCHIVE: Timer Circuit needed

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Posted by Frank Angel (Member # 248) on 09-07-2011, 04:24 AM:

The landlord has installed a new video intercom in our apartment. Spiffy. Really nice one with a color screen. It can either sound one of those annoying digital telephone sounding rings which both of us hate OR, its chirp can be turned OFF and it gives you the choice of a contact closure so you can use whatever bell device you want.

Here's the problem. Our door bell is a common type with two REAL tubular chimes that ring the standard DING, DONG when voltage is applied and released. We like these REAL chimes --the artificial ones with a little 3 inch speakers suck.

These two tubular chimes are struck with a spring loaded hammer that is pulled in by a solenoid when voltage is applied and it hits chime #1. When the voltage stops -- in normal situation, that's when the visitor releases the doorbell button -- the hammer slaps back and hits chime #2; this happens in fairly rapid succession, as in DING .5 to 1 second, or for however long the guy holds down the button.

Problem now is, the new intercom closes the relay supplying the 12vdc to the solenoid not for 1 second, but for about 20-25 seconds. So now we get a DING.....(20 seconds).....DONG. She doesn't like her dongs that long.

The way I play movie soundtracks -- at correct Dolby reference, of course -- I need more bell strikes in more rapid succession if we are going to hear if someone is at the door. So what I am looking for, is a circuit that will time out in say 1 second after the voltage is applied; voltage OFF will release the solenoid and let the hammer hit the second chime. Then the presence of the 12volts which is still there will charge the circuit and 5 seconds later will send 12v for a 1 second ON/OFF cycle again, 5 secs to recycle and so on until the intercom stops sending 12 volts. So when 12v is applied for 20 seconds, the end result will be: 12v ON 1sec OFF 5 secs -- 12v ON 1sec OFF 5 sec, etc., for as long as the 12v is present.

That will give us a succession of timed DING, DONGs so we won't miss visitors. I have no idea how you compute the different timers. Easy to get an even ON/OFF cyle, but how to get one at 1 second with the other at a 5 second wait? Without this modification, we will never hear when someone is the door when we are watching a movie. Then again, maybe that is a good thing considering how anti-social and nasty I get when 1) we are interrupted during a movie by someone AT THE DOOR, and 2) when people DO come in, there is that 70/30 chance that during the movie they will want to TALK to me. Of course the MAIN reason that I CAN'T miss the door is that I won't be able to get the PIZZA DELIVERY. So you see, I HAVE to solve this problem.

Posted by Frank Cox (Member # 6258) on 09-07-2011, 12:21 PM:

This isn't exactly what you asked for, but a common solution to having a doorbell in a noisy environment is to use a flashing light instead of a chime. All you need is a relay and the light, which could be anything up to a strobe or even something like a police emergency light.

I have seen announcement lights like this pre-built including the relay for use as telephone bells, so depending on what you want you might not need to build anything.

Posted by Andy Frodsham (Member # 4061) on 09-07-2011, 12:33 PM:

Try some of the time modules listed on this site.

Good luck, Frank!

http://www.quasarelectronics.com/

Posted by Scott Norwood (Member # 30) on 09-07-2011, 12:34 PM:

What about having the contact closure engage the mute function on your sound processor so that you could hear the doorbell?

Or have it bring up your house lights, if you have an electronic dimmer (Kelmar, etc.).

...or just go with the flashing light option.

Posted by John Hegel (Member # 628) on 09-07-2011, 04:47 PM:

What about something like this?

grainger timer

I know you don't want a constant 20 seconds of dinging and donging; but if you could live with it, an automotive turn signal 'blinker' would work.

Posted by Randy Stankey (Member # 64) on 09-07-2011, 05:17 PM:

Make a 555 timer circuit and set it up as one-shot.

Upon closure of the input contact, an R/C time circuit holds the output contact closed for N-seconds based upon the resistor and capacitor values then releases until the input contact releases and resets the circuit. Use a 24 volt reed relay to activate the chime.

You can find the schematics on the internet and the parts can be obtained from Radio Shack or similar places. Should cost $30 to $50. Less if you have parts lying around the house.

Posted by Louis Bornwasser (Member # 3063) on 09-07-2011, 06:01 PM:

You can purchase a time delay relay from Potter & Brumfield with an adjustable release. Louis

Posted by Frank Angel (Member # 248) on 09-14-2011, 10:49 AM:

Thanks guys. Two solutions: 1) a friend says he'll put together a capacitor/resistor circuit with a relay that charges when the voltage is applied and triggers when it reaches full 12v, then it activates the mini relay which rings the bell and quickly discharges the circuit, which then charges up because the voltage is still present, and so on. He says it will work like a charm and he can even add a pot to allow me to adjust the timing.

And 2) while he is coming up with that for me, I've already been putting together a miniature DC synchronous motor with small gear box that slowly turns a cam next to which I glued a mini-pushbutton switch. The 12v is applied, the motor turns, the cam hits the switch and quickly released it, rotates again (giving me the longer OFF period) then it comes round and hits the switch, etc until the intercom drops the 12v.

Whoever gets his device done first, wins. Personally I would rather go with a no-mechanical solution, but I will be happy with either as long as it works, is small and cheap.

And again, thanks for your suggestions.

Posted by Randy Stankey (Member # 64) on 09-14-2011, 11:00 AM:

Maybe, but a Rube Goldberg version would be really cool.

The motor turns a pulley which raises the weight which hits the lever that drops the bowling ball which rolls down the ironing board and into a bucket which pulls on the rope that opens the window that lets the wind blow which makes the newspaper fly off the table..... etc... etc...

[Big Grin]

Posted by Frank Angel (Member # 248) on 09-15-2011, 07:47 AM:

Randy, bet most of the techies here on FT have been there, made that!

Posted by Joe Redifer (Member # 3) on 09-15-2011, 05:56 PM:

Ummm.... how do you get away with playing movie soundtracks at "Dolby Reference" in an apartment without being murdered by your neighbors? Living spaces with shared walls are truly evil.

Posted by Don Sneed (Member # 955) on 10-02-2011, 10:34 PM:

cool idea...

Posted by Bruce McGee (Member # 131) on 10-03-2011, 03:57 PM:

I was wondering if the 20-25 seconds the solenoid would be energized would cause the coil to burn out?

I like my ding and dong to work together. When my dong is too long, it sounds like another doorbell is being rung...

I just restored, and rewound the coils on, a 1957 NuTone brass doorbell. The chimes sound elegant and deep. Sure sounds better than what they sell now at the box stores.

Posted by Bob Peticolas (Member # 328) on 10-03-2011, 07:25 PM:

Randy,

One of the Velleman timers at this site will do exactly what you want. It's a "VM188 1Sec – 60Hr Pulse-Pause Timer Module"

http://www.quasarelectronics.com/

Posted by Frank Angel (Member # 248) on 10-04-2011, 10:06 AM:

Bob, that is PERFECT. I can scrap the motor & cam deal and go with this. Thanks.

Pulse-Pause-Pulse Timer Module

quote:
The VM188 1Sec – 60Hr Pulse-Pause Timer Module is a general purpose pulse - pause cyclical timer for various 1Sec – 60Hr Pulse-Pause Timer automation applications. It provides intermittent (ON-OFF-ON-OFF, etc) operation of circuits and equipment.

This timer actives the relay for a user-set Pulse time between 1 second and 60 hours. Once this time period has elapsed, the relay with turn off for a user-set Pause time between 1 second and 60 hours. This process is repeated with the relay turning on and off for the same time periods until power is removed.

Features
wide timing range
easy time setting
start with:
'pulse'
'pause'
single shot
loop
applications:
blinking of lights
pulsed operation of buzzers....

I mean, it's like it was MADE for my app!

And Bruce, yes the solenoid WILL burn out if it is pulled in too long.

Like you, I love the sound of real tubular chimes. The unit I have has the smaller sounding plates that are struck, but right under them, much longer brass tubes are hung into which the sound resonates and gives it a really sweet, rich full tone.

JoAnne says to just buy the electronic units for 20 bucks and be done with it. Those not only play MP3 synth "chimes" but something like 2 million tunes that no one wants to hear every time someone is at the door. Not to mention they have all the sonic quality of a cell phone speaker. [puke]

I prevail on this one.

Posted by Randy Stankey (Member # 64) on 10-04-2011, 10:58 AM:

http://www.film-tech.com/uploads/uploads0503/doorbell.jpg

P.S.: It's not a JPEG. Download it and change the suffix to .AIF