Re: Electronics help needed, resistor keeps failing...

["Jon Whiten" <jon.whiten@xxxxxxxxx>]

Is this right?

Assuming Power = V x V / R (see
http://www.the12volt.com/ohm/ohmslaw.asp
) then the power dissipated
by the resistor at 250V would be 250 x 250 / 47000 = 1.33Watts.

So I guess either the resistor value is too small or the power rating
is insufficient.

J


On 3/30/06, Steve Edwards <edwards_sj@xxxxxxx> wrote:
> I have recently fitted a AWM2 micromodule to control and indicate the
> status of my heating.
>
> Information here:
>
> http://www.automatedhome.co.uk/modules.php?name=News&file=article&sid=1652
>
> http://tinyurl.com/pg9u4
>
> I had a problem where a neon light was showing as lit all the time
> even when the module was lit, I found something about it on the
> clipsal site:
>
> --
> 30N-COLOUR A 250V - neon indicator (OTHER COLOURS)
>
> Note: Inductive loads occasionally cause neons to glow in OFF
> position. To prevent this, place a 47k., 0.5W 240V resistor across the
> terminals.
> --
>
> I bought a resistor from maplin and once fitted it did indeed solve
> the problem.
>
> However, the resistor fails after about a month, it's done this twice
> now, any ideas why this is happening?
>
> Cheers
>
> Steve
>