Voltage drop in bell wire

[frank999]

I can't get a battery powered (4x1.5v) door bell to strike, when I test it with the cable run of 5/6 metres using 2 strands of a spare phone cable. Short across the terminals on the unit itself and it strikes happily.

Could I be getting voltage drop ?

 

[securespark]

Have you tried it with a similar length (6m) of thicker cable?

 

[frank999]

No I've not tried that - thanks, I could try a few more strands of the phone cable (which I embedded in plaster).

Phone cable is a tiny dia. cable, a 2 core speaker cable is bigger at about 0.5, could try that - if I ended up with such a cable wouldn't this flatten the batteries much quicker though ...

 

[flameport]

wouldn't this flatten the batteries much quicker though

No.
Larger cable = lower resistance in the wires = larger percentage of the power goes to operate the bell, rather than being wasted in the cables.

With properly sized cable, slightly more power will be used, but that's only while the button is being pressed, and is the difference between it working properly or not at all.

 

[bernardgreen]

when I test it with the cable run of 5/6 metres using 2 strands of a spare phone cable

Is this cable continuous,? is there a phone socket in the run where the "spare" conductors have not been connected.

 

[ban-all-sheds]

Why are you trying to use phone wiring for a bell?

 

[JM2]

Bell wire (of old) was substantial stuff, if a pain to work with in confined areas, and designed for the relatively high currents for such bells.
Phone cable (as in internal cable) is quite the opposite and 5/6 meters (x2 really, 10/12m) will have added significant resistance on its own - it was designed for internal telephone use (c. 50mA loop).

 

[SUNRAY]

Bell wire (of old) was substantial stuff, if a pain to work with in confined areas, and designed for the relatively high currents for such bells.
Phone cable (as in internal cable) is quite the opposite and 5/6 meters (x2 really, 10/12m) will have added significant resistance on its own - it was designed for internal telephone use (c. 50mA loop).

Substantial?
By sheer coincidence I ripped out some bell wire a few days ago, it is the coloured plastic twisted stuff.
I've tried measuring the 7 strands with a cheap electronic vernier, the best I can say is it's about half the size of 0.2mm strands

So (0.1 / 2)²x7xπ=0.055mm²

Telephone cable is 0.5mm So (0.5 / 2)²xπ=0.2mm² or nearly 4 times the size.

I would probably only use telephone cable for door bells and have certainly run significantly more than 5m of the stuff.
At my parents house we had an 'under dome' bell in the garage at the end of the back garden as an extension from the 'ding-dong' with a total run in excess of 40m (possibly more than 50). This successfully ran on telephone 4wire and a Woolworths small brown 8V transformer for 25 years and I'll try to check if it still does at 50 years when we do the next landlords check.

 

[SUNRAY]

Why are you trying to use phone wiring for a bell?

Why not? it's only wire.

 

[securespark]

Is this cable continuous,? is there a phone socket in the run where the "spare" conductors have not been connected.

Why are you trying to use phone wiring for a bell?

I don't think the OP is trying to make use of existing phone wiring to run a doorbell, but merely a piece of CW1308 not connected to anything else.

 

[ban-all-sheds]

So you think he chose CW1308 for this application and plastered it in before checking that it worked OK?

... the phone cable (which I embedded in plaster)

 

[JM2]

Substantial?
By sheer coincidence I ripped out some bell wire a few days ago, it is the coloured plastic twisted stuff.
I've tried measuring the 7 strands with a cheap electronic vernier, the best I can say is it's about half the size of 0.2mm strands

So (0.1 / 2)²x7xπ=0.055mm²

...

Nah, old bell wire. The solid (and hence a pain to work with) and substantial stuff. Must have been 1mm² or so each core.
Sounds like you've recovered some old thin speaker wire!

 

[SUNRAY]

Nah, old bell wire. The solid (and hence a pain to work with) and substantial stuff. Must have been 1mm² or so each core.
Sounds like you've recovered some old thin speaker wire!

Ah, I don't know if I've come across what you describe.
What was sold by Woolworths, and other hardware shops a twice the price, as bell wire is the thin twisted flex in transparent coloured plastic. And yes we used loads of it for loudspeaker work back in the day when a bit of extra resistance hadn't been invented in audio.

 

[JohnW2]

What was sold by Woolworths, and other hardware shops a twice the price, as bell wire is the thin twisted flex in transparent coloured plastic. And yes we used loads of it for loudspeaker work back in the day when a bit of extra resistance hadn't been invented in audio.

Not only do I remember it well, but I still have some of it! I can also recall some of the things I used it for (probably around 50 years ago), which I would hesitate to mention here

Kind Regards, John

 

[SUNRAY]

Not only do I remember it well, but I still have some of it! I can also recall some of the things I used it for (probably around 50 years ago), which I would hesitate to mention here

Kind Regards, John

It's just occurred to me I may have come across something like you describe a little while back, basically figure of 8 with solid cores but the shape was sort of 2 squares rather than double barrels. It was used for temp sensors in a Honeywell BMS system, I may even still have some in a bag that hasn't got as far as the scrap yard yet.

I expect I still have some old loudspeaker leads made with the twisted stuff in a long since disused suitcase full of PA bits.

That reminds me I really need to sort it out and presumably - get rid.