Author Topic: Touch operated lamp  (Read 26835 times)

Offline kurnal

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Touch operated lamp
« Reply #15 on: June 23, 2007, 11:20:14 AM »
Good point John. I had missed that message when following the thread.

Offline Martin Burford

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Touch operated lamp
« Reply #16 on: June 23, 2007, 11:28:53 AM »
Tall Paul
A simple question.................what was the rating of the bulb in the lamp ?
Conqueror.

Offline Tall Paul

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Touch operated lamp
« Reply #17 on: June 23, 2007, 12:24:26 PM »
The Bulb was a standard 60W, this was the design bulb for the lamp.  As a point of interest, the metal frame to the wicker drawers was also alongside, and possibly in contact with, a central heating radiator.  I can't be certain of actual contact because fire crews may have moved it slightly.

In terms of fire spread, a number of indicators point to the fire starting in the vacinity of the lamp.  The lamp was upright. There is of course a possibility of the bulb coming into contact with the shade...

But it is the electronics element that I am seeking help on, because I am interested in whether a metallic contact can simulate the touch of a human hand, and whether sufficient heat energy, a relationship of power and time, could result in a fire developing within and ultimately external to the body of such a lamp.

As I have mentioned before - this is not to pin down the cause in blindness to all else, but to discover whether it has the potential to be one of a number of hypothises worthy of persuit.

The lamp was from a major DIY chain.  The chain had returned it to the manufacturers who, having put it through a series of tests, are sure that it did not malfunction.  The internal circuitry, however, was severely damaged by fire, with a greater fire damage within the lamp body than external to it, in relation to intensity not area.  That is why it is not being laid aside as a potential cause at this stage.

The reason that trading standards are involved is that IF a previously unanticipated fault could lead to ignition, then consideration will need to be given to either providing warnings with the lamp, or moderation of the design.

Offline Martin Burford

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« Reply #18 on: June 23, 2007, 04:23:11 PM »
TP
Did you examine the plug.and what was the amp of the fuse used ?
Conqueror

Offline kurnal

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Touch operated lamp
« Reply #19 on: June 23, 2007, 11:10:52 PM »
This site may be of interest.

http://www.repairfaq.org/REPAIR/F_appfaq7.html

Have done a bit of digging and find there are several different modes of operation. In some other types there is an oscillator running and the touch of the finger affects the capacitance controlling the oscillator and the change in frequency is amplified, as John suggests.

I am not really surprised that the manufacturers say there was nothing wrong with the lamp. They would wouldn't they!!

I suppose  as the lamp was earthed it is more likely to be an oscillator controlled lamp as any mains  hum induced by touching would go to earth.

I wuld still be inclined to check for earth or the neutral  faults.
intermittent contact with  the bed frame may  alter the frequency  and cause the repeated operation as you suggest but in itself you would not expect this to cause overheating

We still may have a fault on the PC board capable of causing a fire. After all this is why we say dont leave your TV in standby mode.