I have an LED torch, 3 volts, single LED.

It has worked all right for several months. Now, when turned on, the light
emitted is not constant but flashes several times per second.
It is the same with new batteries fitted.

Why might this be happening? What characteristic of LED torches is
involved? Can it be cured?

What make and model tourch is it? There are many different circuit
designs around.

Some early designs of rear LED lights (Vista) flashed all the time but
at a high rate so it looked like it was on constant. The reason being
that it saved power and extended battery life. Rear lamps don't need to
be as bright as front lamps. A change in the value of a resistor damage
from o water or battery contents could alter the frequency.

Others seem to have a dedicated chip bonded onto the PCB. Maybe a fault
has developed and it keeps resetting.

Need more information really.

oops!

looks like I slipped into automatic cycling mode. The points I made are
still valid. Just ignore references to rear Lights

"Rob" wrote in message
oups.com...
oops!

looks like I slipped into automatic cycling mode. The points I made are
still valid. Just ignore references to rear Lights


Rob,

Thank you for the comments.

The PCB in the torch has the name Lomak; all there is on one side of it is a
microswitch, and on the other side all that can be seen is three big blobs
of solder. Presume there must be additional circuitry of some sort somewhere
amongst that lot.

I bought the LED torch thinking it would be more convenient because there
would be no filament bulb to go at an inconvenient time, leaving one in the
dark. However, it seems as though one weak point (the filament going) has
been replaced by another weak point (the circuit board developing a fault).
With the former, the bulb can be easily replaced, which is not the case with
a circuit board. The LED torch is not unqualified progress.

Regards,

Cycle.

It's hard to say without more information.

Do you have a model number, number of batteries used and type of
battery (AA, AAA, ?)

Are you sure the blobs are really solder? Can you see any black blobs?

I think that most white LED tourches these days use an LED driver to
control them. Some tourches will deliberately have a flashing function.
It's alot cheaper to make a driver that does it all and simply not use
some of it's functionality when creating different products


In which case it's possible that your tourch has this hidden flashing
capability and it has now been activated by some means. Maybe an
unproperly terminated input on the chip has "latched up".

Has the tourch got wet or been in a damp environment? It may be being
affected by damp. Take it apart and leave somewhere for a while to
dryout completely. Probably leaving it outside would work considering
the weather.

To get rid of a possible latchup problem, which may well be being
maintained by a small residual charge in the chip, take it apart.
Remove all batteries and short together any contacts on the PCB for the
batteries.
Maybe even leave it for a while without the batteries. Charge will
eventually leak away.

Are you sure that the new batteries are really new? If there isn't
sufficent voltage available then you may get unpredicatable behaviour.
Eg. flashing.

Did the tourch cost a lot? There's no guarantee that a traditional
tourch wouldn't develop a problem, although it would be easier to
diagnose and fix.

Hope this helps.

Note. Please don't short any batteries together!

"Rob" wrote in message
oups.com...
It's hard to say without more information.

Has the tourch got wet or been in a damp environment? It may be being
affected by damp. Take it apart and leave somewhere for a while to
dryout completely. Probably leaving it outside would work considering
the weather.

To get rid of a possible latchup problem, which may well be being
maintained by a small residual charge in the chip, take it apart.
Remove all batteries and short together any contacts on the PCB for the
batteries.
Maybe even leave it for a while without the batteries. Charge will
eventually leak away.

Are you sure that the new batteries are really new? If there isn't
sufficent voltage available then you may get unpredicatable behaviour.
Eg. flashing.

Did the tourch cost a lot? There's no guarantee that a traditional
tourch wouldn't develop a problem, although it would be easier to
diagnose and fix.

Hope this helps.


Rob,

Thank you for your input.

I shall just throw the torch away, in the circumstances. It is a single LED,
two AA cell model sold under the Pifco name, and at the cheaper end of the
range. PCB says "Lomak 310803 PCB-00". It has worked all right for eight
months or so, and then suddenly decided to become a flash(ing)-light.

I tried your drying/shorting ideas, but without success.

Regards,

Cycle