Touch control lamps only works when switch wire is disconnected.

[eveder]

I have fitted a touch control switch to a lamp, (I have done many no problem)…..However in this table lamp with a cast iron base the device does not operate when connected to the base? But when unscrewed the light turns on and 3 stage dims as it should. Any ideas welcome please.

 

[James]

Can you post some pictures?

 

[eveder]

I have fitted a touch control switch to a lamp, (I have done many no problem)…..However in this table lamp with a cast iron base the device does not operate when connected to the base? But when unscrewed the light turns on and 3 stage dims as it should. Any ideas welcome please.

 

[eveder]

Can you post some pictures?

 

[eveder]

It works fine before I connect it to the base. This is second one I’ve tried, both work fine on test.

 

[James]

Is the control wire designed to be connected to an earthed metallic base?

 

[eveder]

Is the control wire designed to be connected to an earthed metallic base?

No, the touch control works on capacitance, there is no Earth.

 

[James]

That base should be earthed unless everything else is double insulated (looks like it is not)

 

[eveder]

No, the touch control works on capacitance, there is no Earth.

That base should be earthed unless everything else is double insulated (looks like it is not)

All good, it has a ceramic double insulated lamp-holder.

 

[littlespark]

Aside from the lamp holder, the connection within the base should be inside a plastic box….. if the metal base isn’t earthed.

What happens if a live wire becomes detached from the connector?

The plastic box also has strain relief, so there is zero chance a loose wire can escape and find its way to touching the metal.

 

[eveder]

Aside from the lamp holder, the connection within the base should be inside a plastic box….. if the metal base isn’t earthed.

What happens if a live wire becomes detached from the connector?

The plastic box also has strain relief, so there is zero chance a loose wire can escape and find its way to touching the metal.

Sure, it will be in a inline plastic box like in the photo, all joints will be SN-48B crimp connected, this is the only difference to the other base mounted touch control switches I have fitted before inside the lamp base.
My issue is that the lamp works fine when I touch the disconnected yellow switch wire, but when it is connected to the lamp base and touch the metal lamp the G9 halogen bulb glows in the 1st dimmed stage and will not cycle through the 2nd, 3rd stage dimmed and off.
Many Thanks for all input.

 

[Avo Mk8]

Try a thick insulating/dielectric layer stuck on the underside of the cast iron base, and try it (stood on its new insulation) away from that (possibly static dissipative) cutting mat?

 

[eveder]

Try a thick insulating/dielectric layer stuck on the underside of the cast iron base, and try it (stood on its new insulation) away from that (possibly static dissipative) cutting mat?

I have tried this and still have not got to the bottom of the problem,
It seems the sensor only works and cycles through the 3 stage dimmer when the touch sensor wire is disconnected, then tapped anywhere on the metal work of the lamp??
When the touch sensor wire is connected it will switch to the 1st stage dimmer then “stick” not switching to 2nd, 3rd stage dimmer and finally off.
The unit has been attached to a brass trumpet, oil can converted to lamps and works fine!!! Bizarre.

 

[Avo Mk8]

I have tried this and still have not got to the bottom of the problem,
It seems the sensor only works and cycles through the 3 stage dimmer when the touch sensor wire is disconnected, then tapped anywhere on the metal work of the lamp??
When the touch sensor wire is connected it will switch to the 1st stage dimmer then “stick” not switching to 2nd, 3rd stage dimmer and finally off.
The unit has been attached to a brass trumpet, oil can converted to lamps and works fine!!! Bizarre.

Yes, curious
It seems to me there may be some leakage or excessive capacitance introduced by the flex running through the base, or by the lamp holder itself.
Could I suggest you mechanically separate the bulb holder from the metal lamp base, maybe just having the mains cable going in at the bottom and out at the top, and the bulb and holder away from the lamp base, and see if the effect persists.
Or maybe try a different piece of flex in case there is something peculiar about that?

 

[Avo Mk8]

Follow up!
Simple question - if you touch and continue to hold on to the sensor wire, does the dimmer behave in the same way; ie lamp stays on at the dimmest setting. Or does it do something different?