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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.
 
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.
 

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Is the control wire designed to be connected to an earthed metallic base?
 
That base should be earthed unless everything else is double insulated (looks like it is not)
 
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.
 
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.
 

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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?
 
Last edited:
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.
 
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?
 
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?
 
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?
Thanks Avo for your continued interest.

If I touch and hold the sensor wire, it will stay on the dimmest setting, it only changes when released and touched again….. (as it should).
Once connected to the base (or any other metal part of the lamp, it sticks at dimmest stage 1.

To compound my confusion and found out by accident, if I connect the touch sensor as normal, then lean on (touch) another double insulated lamp with a metal base, the problem lamp operates perfectly through all 3 dimmer stages and off.!!!

I have a pair of these lamps to repair and they both have the same problem.
 
Thanks Avo for your continued interest.

If I touch and hold the sensor wire, it will stay on the dimmest setting, it only changes when released and touched again….. (as it should).
Once connected to the base (or any other metal part of the lamp, it sticks at dimmest stage 1.

To compound my confusion and found out by accident, if I connect the touch sensor as normal, then lean on (touch) another double insulated lamp with a metal base, the problem lamp operates perfectly through all 3 dimmer stages and off.!!!

I have a pair of these lamps to repair and they both have the same problem.
OK, so you have shown that the sensor is behaving as we might expect if the troublesome lamp is 'loading' the sensor because of leakage or excessive capacitance.

You need the minimum of capacitive coupling between all the metalwork and L an N mains wires. Is the wire you have running in the 'stalk' of the lamp three core by any chance? I think that might be a problem.
It may also be that cable in the 'stalk' is the issue?
 
OK, so you have shown that the sensor is behaving as we might expect if the troublesome lamp is 'loading' the sensor because of leakage or excessive capacitance.

You need the minimum of capacitive coupling between all the metalwork and L an N mains wires. Is the wire you have running in the 'stalk' of the lamp three core by any chance? I think that might be a problem.
It may also be that cable in the 'stalk' is the issue?
View attachment 66051648158__281B043D-DA6F-4236-9AE6-931F81CE77D5.MOV
 
2 core to the sensor
3 core to light L N to lamp and “sensor wire” to base only
Sorry, I 'm not clear on the overall wiring.
You say earlier the sensor is inline. is this the first lamp you have done with this configuration. Presumably the sensor box would be in the lamp base if you could accommodate it there?
So there is a length of flex between sensing box and lamp, carrying L, N, and sense? How long is that?
It seems to me the sense wire is being loaded up with more capacitance or leakage that usual.
Does it run in the 3-core flex for very long?
 

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