Advice on Introducing a Toggle Switch to a Plug-in Lamp Circuit


Postby Thebookstamper » Tue May 10, 2016 11:01 am

Hi all,

I am familiar with some basic lamp wiring, as I make my own lamps for use at home, but would like to to try something new. I'd like to introduce a toggle switch to a lamp circuit, I've seen it done before (like so: https://www.etsy.com/uk/listing/2625744 ... ?ref=hp_rv ) but I've never used toggle switches before so it's not that intuitive to me.

I bought a DPST toggle and did some experimenting last night, but no joy so far. Here's a link to the one I bought: http://www.ebay.co.uk/itm/401051331207? ... EBIDX%3AIT . It has four screw terminals (numbered 1, 4, 3 and 6), so I tried connecting the live and neutral wires to those in various combinations (as I wasn't sure where input/output would be) by stripping the insulation, and hooking the wires around and under the head of the terminal screws.

Obviously nothing happened at all each time I turned it on. I've probably missed something really obvious. I'm also wondering if it's the fact I'm using a DPST rather than SPST, would that make more sense? I use 3 core cable with a brass lampholder, so am earthing in the plug and lampholder, but obviously leaving the earth cable unconnected where the toggle is introduced, is this an issue? I could easily switch to a bakelite lamphoolder and 2 core cable if so.

I am really grateful for any advice anyone can give on this, and can provide more info (including a picture of the screw terminals) if required.

Thanks
Thebookstamper
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Postby ericmark » Wed May 11, 2016 3:49 am

The switch is sold as an automotive switch and although you do have some wagons with insulated return used for petrol tankers and the like in the main they are chassis return. Reading the switch it states 125 volt so clearly not for use with UK 230 volt supply.

You can get 230 volt types in the main there is a plastic shield between the two poles keeping the neutral and line very well apart.

http://uk.rs-online.com/web/p/toggle-switches/5185314/

Some of the switches sold in the 1950's and 60's in places like Woolworths the toggle was actually live. They were for use with batteries only. Not seen any in resent years but buying random switches which clearly state "12V ON/OFF Car Dash" even if the picture shows 125V is rather dangerous as it may not isolate. Switches for 230 volt AC have a minimum gap when switched off. The good switches also have a seal so dirt and water can't get in from the toggle and are normally used on an earthed panel. Unless the switch is marked double insulated then I would always earth it unless all plastic.

The link I have given has a data sheet which states Dielectric strength 2500 V rms min - between terminals and frame so clearly that switch should be OK.
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Postby Thebookstamper » Sat May 14, 2016 5:32 pm

Hello,
Thank you so much for your reply, I ordered the toggle switch you recommended and have just had a go at introducing it into my basic lamp circuit. I soldered the live and neutral wires to the connection points, on either side of the plastic barrier, but unfortunately nothing happened again.

I suspect I've overlooked something obvious, I tried to upload a picture directly onto this post but it wouldn't work for some reason, although it was only 80KB, so I've posted it elsewhere online and added this link to demonstrate what I mean: https://www.tumblr.com/blog/thebookstamper

One cable leads to the plug and the other leads to the lamp holder, what am I missing?

Again, many thanks for any advice.
Thebookstamper
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Postby ericmark » Sun May 15, 2016 6:36 pm

The picture shows a guy on a skate board. I have to admit I have also has problems posting pictures on this site. You should be using centre pair and one set of outer terminals.
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