18v supply into 16v entry phone.
Devany
I have an existing, failing, video phone entry system. Not completely
broken, but it needs replaced.
The handset uses a 18v power supply, which the long ago installer
embedded someplace unknown, and I don't want to hack the plaster off to
find out where.
Could I replace the handset with a 16v system? i.e. I found a potential
replacement, but it only needs 16v - could I plug the 18v supply into it
and expect it to work properly?
I measured the supply and it actually reads 18.5v
Any advice appreciated.
Harry Bloomfield
Is that AC or DC?
Assuming DC, you might be able to get away with putting diodes in
series to drop the voltage. Each forward biased diode drops 0.6 to 0.7
of a volt. Three in series would drop around 1.95v, so the 18v would
become 16v.
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
NT
Most small appliances work fine on similar voltages. But there are a
minority that seriously object.
If they're both dc supplies you could use a couple of diodes, each
will drop around 1v under load (not 0.6). If theyre not both dc its
more complex.
NT
Devany
Yes DC.
Thanks for the tip. I foresee a visit to Maplins.
Arfa Daily
"NT" <meow...@care2.com> wrote in message
news:bdc06203-0276-42c0...@b15g2000yqd.googlegroups.com...
NT
Check of course, if it's a typical coaxial DC plug, that the polarity is
correct. Some years ago, the Japs had a thing about the centre pin being
negative. Then, everybody else seemed to standardise on the centre being
positive. If you put the diodes in series, then if you had got wrong
polarity, and you'd put them in assuming that tip was +ve, then no harm
would come to the equipment - it just wouldn't work.
Arfa
Tinkerer
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:8yRJm.53700$1i2....@newsfe07.ams2...
I picked up a handy (cheap) little gadget in Maplin's that identifies the
polarity on those coax plugs. Already been useful on several occasions.
http://www.maplin.co.uk/module.aspx?moduleno=32161
--
Tinkerer
NT
wrote:
> "Arfa Daily" <arfa.da...@ntlworld.com> wrote in message
>
> news:8yRJm.53700$1i2....@newsfe07.ams2...
>
>
>
>
>
> > "NT" <meow2...@care2.com> wrote in message
In all honesty I'd put that £1.79 towards getting a multimeter.
NT
geoff
<invalid...@invalidaddress.invalid> writes
And for a couple of quid more, you could have bought a multimeter, which
would have been SO much more useful
--
geoff
Tinkerer
"geoff" <ra...@kateda.org> wrote in message
news:uh2oO8G9...@demon.co.uk...
I've got a multi meter and find it confusing to use; maybe because the
person who wrote the instructions assumed that everybody reading it was
already fully acquainted with the instrument and held a diploma in
electronics - some pages look more like a mad scientists formulas. This
little gadget on the other hand is dead simple (put in the plug and a light
comes on) and it fits in my pocket.
--
Tinkerer
geoff
<invalid...@invalidaddress.invalid> writes
So who ties your shoelaces for you in the morning ?
>This
>little gadget on the other hand is dead simple (put in the plug and a light
>comes on) and it fits in my pocket.
Set the dial to volts DC, stick one probe on the centre pin, one on the
outer sheath and look at the display
simples
--
geoff
Arfa Daily
Well yes, it is simple to those of us who use multimeters every day in our
working lives, but if the little Maplin gadget suits Mr Tinkerer, then I see
no problem with that ??
Arfa
Tinkerer
Actually, there comes a time when those new fangled shoes with velcro
fasteners are very attractive ;o)
>
>>This
>>little gadget on the other hand is dead simple (put in the plug and a
>>light
>>comes on) and it fits in my pocket.
>
>
> Set the dial to volts DC, stick one probe on the centre pin, one on the
> outer sheath and look at the display
>
> simples
I shall give that a try. But in fairness, I was given the multi meter some
years ago and have only used it a couple of times for simple continuity
tests, and that only because I couldn't find my old home made battery and
bulb test lead that I originally put together for setting the timing on
cars. You will gather that I can handle mechanicals happily but
electronics are a closed book.
--
Tinkerer
Owain
> I shall give that a try. But in fairness, I was given the multi meter some
> years ago and have only used it a couple of times for simple continuity
> tests, and that only because I couldn't find my old home made battery and
> bulb test lead that I originally put together for setting the timing on
> cars. You will gather that I can handle mechanicals happily but
> electronics are a closed book.
I hardly ever use the multimeter now - got an electric test which
shows a range of voltages on an LED ladder and beeps with continuity.
No worries about sticking the multimeter on the wrong range onto a
live circuit and frying it.
A cheaper version of this sort of thing
http://www.screwfix.com/prods/61568/Electrical-Supplies/Electricians-Tools/Circuit-Testers/Kewtech-KEW1700-Voltage-Tester
Owain
geoff
There's really no magic to it
From earlier, it seems that your brain just switches off, you stuck it
on an inunderstandable" pedestal - forget the formulae and whatever, all
you need to do is measure a value presented between two probes, that's
it
Its not a hard barrier to overcome if you try
--
geoff
geoff
<6fe3ad82-6edd-436a...@j4g2000yqe.googlegroups.com>,
Owain <spuorg...@gowanhill.com> writes
Most multimeters are self ranging, and even those which aren't won't
blow anything up if connected to the wrong range (although measuring the
mains when set to resistance might well do)
--
geoff
Owain
> But its only a crude multimeter, at the end of the day
Yes, but I think better suited to the purpose. And it means the
multimeter can stay in the nice clean electronics box and not risk
getting dropped.
> Most multimeters are self ranging, and even those which aren't won't
> blow anything up if connected to the wrong range (although measuring the
> mains when set to resistance might well do)
Measuring the mains when set to resistance is exactly the sort of
error I'm likely to make :-(
Owain