18v supply into 16v entry phone.

Devany laid this down on his screen :

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.

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

Thanks for the tip. I foresee a visit to Maplins.

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

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

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.

s.

NT

In message , Tinkerer writes

And for a couple of quid more, you could have bought a multimeter, which would have been SO much more useful

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.

In message , Tinkerer writes

So who ties your shoelaces for you in the morning ?

Set the dial to volts DC, stick one probe on the centre pin, one on the outer sheath and look at the display

simples

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

Actually, there comes a time when those new fangled shoes with velcro fasteners are very attractive ;o)

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

In message , Tinkerer writes

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

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)

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.

Measuring the mains when set to resistance is exactly the sort of error I'm likely to make :-(

Owain