This article covers choice and fitting of wired doorbells.
==Kit or self assembled=Doorbell kits are easy, as you don't need to worry about voltage, [[Electricity Basics|ac versus dc]], regulation or anything else. You even get all the bits in one pack. If you're not too fussy, these pre- packed kits make life easier.
Assembling your own system from diverse parts is more complex, but not very difficult. And of course its much more flexible.
==Sounders=You get a choice of * Bell * Ding dong * Electronic
Mechanical sounders tend to produce voltage pulses on the [[Low Voltage Wiring|cable]], so mixing electronic and mechanical sounders on one circuit is not best practice, and may kill the electronic sounder.
Generally speaking, and these aren't always the case: * bells are the loudest * dingdongs are medium volume, but much more pleasant to the ear * electronic sounders can produce various sounds, but generally aren't so loud.
==Switch=The bell push is just a momentary switch. It doesn't matter whether the switch goes in the -ve or +ve fead to the bell. Many also have a low power [[Filament Lamps|filament bulb]] inside, which lights when the switch isn't being pressed.
Since it switches low voltage at not much current, the switch can be pretty much any type of momentary push-to-make switch. Custom switches are perfectly DIYable where a character bellpush is wanted.
Improvement in switch reliability and longevity can be gained by fitting a [[snubber]] across the switch contacts. This also eliminates one of the causes of interference to audio equipment & digital TV. Snubbers are not usually fitted, but if you put time into making a fancy switch it makes sense to take another minute or 2 to make it last.
Note that mains [[snubbers]] aren't effective for low voltage use. More suitable component values would be 15-22 ohms plus 10uF (for dc systems) or 15-22 ohms & 1uF non-polar for ac systems.
A [[Filament Lamps|filament bulb]] in the bellpush acts as a [[snubber]], but these are often not fitted, and when they are they're often not replaced when they fail. Snubbers last for life. [[LED Lighting|LED lights]] in bellpushes don't act as snubbers.
==Circuit diagrams= Mains | | ____|__|_____ | | ______ | TRANSFORMER |------------------------------| | | typically | | Bell | | 6-8V AC |------+ +------------|______| |_____________| | | | | | | | | | | | | | | +--Switch--+
Basic system diagram
This can be optionally expanded as follows:
Mains | | ____|__|_____ | |---+--------------------+---------+ | | | ___|__ ___|__ | TRANSFORMER | | | | | | | | === C | Bell | | Bell | | | | |______| |______| | | | | | |_____________|---+--+ +------+---------+ | Light | | / \ | +--Switch--+ | \ /| | Snubber | | | | | | Light | | / \ | +--Switch--+ | \ /| | Snubber | | | | | | Light | | / \ | +--Switch--+ \ / Snubber
Circuit with optional extras
==Kit Power supplies=The power supply in a kit will be chosen to match tbe sounder. These are often ac transformers.
==Other power supplies=If assembling your own system you'll need to do a bit hinking re the power supply.
Standard bell transformers can be used with a lot of sounders, but not all. They are the simple choice if your sounder will accept the ac voltage the transformer produces. If it won't, the ac may kill the sounder. The next section explains supplies for sounders requiring dc, and how to run any sounder on a [[wallwart]]. (Ac sounders can run happily on dc.)
For dc [[wallwart]] supplies: * for electronic sounders, use a wallwart of the sounder's rated voltage * for mechanical sounders, use a 1A wallwart of 3v above the sounder's rated voltage. Adding a 2200uF-4700uF 16v (or more) capacitor across the transformer's outputs (connecting + to +, - to -) can improve reliability & volume.
The above will work fine in nearly all cases.
==Ü power supplies explained==If you want to understand power supply choice properly, and pick the optimum supply, here's the deal:
Electronic sounders use low power, and will run fine off the rated voltage of supply. No capacitor is required.
Mechanical bells and ding-dongs use a lot of current when they're sounding, well above the rated current of your average [[wallwart]]. This isn't a problem for the wart, since it only delivers this current for a tiny percentage of the time. However it does have implications for the sounder. The current draw results in the wart delivering well below rated voltage during sounding, due to transformer copper losses. This drop is partly made up for by picking a higher voltage wart.
An added issue is that mechanical sounders suffer from stiction and some require an initial current & voltage kick to get them moving freely, so they work well & give good volume. The capacitor delivers this, by charging to above on-load voltage and delivering this to the bell for a very brief moment when the bellpush is operated. This is entirely harmless to mechanical sounders.
Most [[wallwarts]] deliver well above rated voltage when off load. This doesn't matter to mechanical sounders since they're not connected, and a momentary overvoltage when connected is beneficial rather than harmful. [[Filament Lamps|Light bulbs]] however do care very much about voltage, and the bellpush bulb should be rated at or above the voltage the wart delivers when offload. A [[multimeter]] will show the off load voltage. Hence ideally the bulb and bell will have different voltage ratings, yet both be powered by the one supply.
==Wiring=[[Low Voltage Wiring|Bell wire]] is the cheapest wire that will do the job, and is the usual [[Low Voltage Wiring|cable]] used. In larger properties, long runs of bell wire can affect operation with mechanical sounders, the solution to this is simply to increase the power supply output voltage to compensate.
Standard 4mm bell wire staples are used to fix the [[Low Voltage Wiring|cable]] to the wall.
Although bells are low voltage circuits, mechanical sounders tend to produce higher voltage pulses on the [[Low Voltage Wiring|cable]], so use of bare [[Low Voltage Wiring|enamelled wire]] is not recommended. For this reason, mixing electronic and mechanical sounders on one circuit is not recommended, and can sometimes kill the electronic sounder.
==Wireless bells=Surprisingly these need no wiring.
Since they run on [[battery|batteries]] they tend to go flat. If you haven't had any visitors in a while this might be why!
==Alternatives=* Mechanical doorbell * Door knocker
==See Also=* [[Special:Allpages|Wiki Contents]] * [[Special:Categories|Wiki Subject Categories]]