So to be clear, I am a Mechanical Engineer that can wire speakers and a radio into my car. Can solder ok. I did lots of wiring when building R/C airplanes and maintaining my old first home.
Problem summary:
When someone holds the door bell button down too long it melts the little plastic plunger in the mechanical wired chime. I would like to know if there is a way to add some "magical" electrical components like resistors or diodes or capacitors that would open the circuit if held longer than 1 second.
Background
1930s era home has wiring that I cannot easily access for front door doorbell button. Basically the rock facade was chiseled out to pull wires for the button. The wires are not in a box and can't be pulled further out. Plus they are "crispy" as in bits broke off the last time we had to work on the screen door and had the bad idea of replacing the switch. No one in the home wants to go to wireless, so we want the struggle of making the wired system work, because, GRM. A wireless system for just the front door has been proposed and shot down.
The side door has a NEST doorbell but the rock facade prevents me from doing an easy install on the front door. I would have to custom fabricate some kind mounting box for the nest doorbell that matches the largely irregular surface of the rock facade. Doable in the future but would have to be prepared to chisel out a bunch of rock or knock a hole into 90 year old pristine plaster walls if the wires broke inside the wall.
So looking for that magical electrical solution at the doorbell chime end of things. Please let me know if such magic exists.
Any reason you couldn't install a relay, the same as you would for headlights? No idea where you would put it, though...
In reply to CJ :
Again magic...I assumed a relay needs two circuits of different power? IDK I just have the doorbell transformer and a single circuit that links the doorbells switches and chime.
There are many ways this could be done, all the way up to severe overkill solutions involving a microcontroller, but the easiest way to do it with minimal parts would be with a thermoelectric flasher. This would force the doorbell to operate intermittently like a car's indicators.
A slow blow circuit breaker :) Something like this if you spec it right so that it trips the bell before it disconnects. We use these things on our fan kits at FM.
https://wiringproducts.com/collections/auto-reset-circuit-breakers-standard-mount
The problem is with the chime, not the button. So wiring at the switch isn't necessary, it's the plunger in the chime that's failing. Can you get a more robust chime? Doorbells run at a lower voltage, so there's a transformer hidden somewhere - is it failing and providing too much voltage for the chime to handle? That might be fun to find, in my case it's near a subpanel.
In reply to GameboyRMH :
I will research a thermoelectric flasher.
In reply to Keith Tanner :
Transformer is new. And working well. The technology variance is similar to a rev limiter. On old engines that was the operator judgement on holding a lever, pusing pedal, etc. Now engine controllers limit over speed. Modern digital doorbells seem to run off 120v and usually wireless or designed to handle someone holding the button down. The wiring is too small to convert to 120V.
So basically if people just pushed and released the button it works fine. If someone thinks it is an old buzzer where you hold the button down to make the buzzer sound longer, they melt the plunger. This is only the second time in 6 years or so. But still, should be able to find a solution.
I don't think you need to convert to 120v. A pretty large percentage of houses still use the old low voltage wiring, including ours. You don't need to go digital and you don't want to because they all sound awful :)
You certainly could do something clever with a microprocessor. Basically, you'd be making a smart relay. But this has been done forever with bimetallic strips, which is what those thermal circuit breakers I linked use. If they carry enough current long enough, they disconnect based on simple heat increase.
Can you measure the draw? That'll make it easier to spec something out.
What is too long? You press a door bell button, you don't hold it down. If someone is holding a doorbell button down and ringing it constantly, breaking their fingers would solve the problem.
In reply to Advan046 :
Keep in mind a solid-state flasher could work as well and would be more efficient, any kind of flasher is a single component that can do almost exactly what you want off-the-shelf.
Wire up the button to an HEI coil. They'll remove their finger in much less than a second.
Who are these people that are holding the doorbell button down for more than a second?
Ok so how do you calculate if the spec of auto reset thermo electric flasher if it is used with 16v AC versus 12V DC?
There shouldn't be any difference between AC and DC for a thermoelectric flasher, the speed it operates at would only be affected by the current going through it. It's basically a self-resetting circuit breaker. To use a solid-state flasher it would need to be made for AC current though. Apparently people are using thermoelectric flashers on bikes with AC electrical systems:
https://www.thumpertalk.com/forums/topic/809582-do-any-blinker-relays-work-with-ac-current/
A solid-state flasher will cost more but it will be easier to set up, their rate is independent of the current passing through them. This one cycles between on and off every 0.4sec:
https://www.ingramproducts.com/products/alarms/alarm-lights/solid-state-ac-flasher#product_cut_sheet
It does have a minimum load though so you'll probably need to add a resistor across the doorbell wires like in the LED example in the PDF.
Thanks for all the help. Just have been traveling for work and haven't had a chance to try it out yet.
