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4th Nov 2006, 4:26 pm | #1 |
Pentode
Join Date: Mar 2003
Location: Mansfield Woodhouse, Nottinghamshire, UK.
Posts: 215
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Economy Variac. Is this a good idea?
If you were to connect a cheap and nasty light dimmer to a radio via an isolating transformer, would the transformer help restore some sort of sine wave, whilst isolating the test radio from the mains?
This could provide a cheap and safer pseudo variac. Has anyone out there tried it, or have you got more sense? I'd like to give it a go but my 'scope's on bricks at the moment. Comments please. Bob. Ps you could use an in-line mains filter as well I suppose.
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4th Nov 2006, 4:44 pm | #2 |
Retired Dormant Member
Join Date: Dec 2003
Location: North London, UK.
Posts: 6,168
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Re: Economy Variac. Is this a good idea?
Not recommended. The nasty edgy waveform from the dimmer will annoy the transformer with unpredictable results. The tranny certainly won't restore the waveform to a nice sine wave.
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4th Nov 2006, 5:43 pm | #3 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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Re: Economy Variac. Is this a good idea?
Hi Bob, I wanted to use an infra-red remote controlled lamp dimmer for turning on power to a transformer but it did not work. The dimmers are meant for mainly resistive loads and shut down if the load is too inductive. I tried to cheat it by making it control a mains relay with a 15W lamp in parallel. It worked but clearly did not like it as operation was a bit hap hazard and the whole set up buzzed loudly. In the end I bought a radio controlled 13A socket. I have a 10 Amp variac which I use mainly for servicing switched mode power supplies in conjunction with an isolating transformer, if you just want to service valve radio's etc. then the series ballast lamp method has a lot to commend it.
Les |
4th Nov 2006, 7:41 pm | #4 |
Pentode
Join Date: Jun 2006
Location: Crawley Down, West Sussex, UK.
Posts: 151
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Re: Economy Variac. Is this a good idea?
Most light dimmers crop the sine wave with a Triac , causing problems with massive noise on the supply.
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4th Nov 2006, 8:14 pm | #5 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
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Re: Economy Variac. Is this a good idea?
Bob - for all the reasons listed, in answer to your question....
NO !!!! I tried it.... Steve P
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29th Nov 2006, 1:55 am | #6 |
Retired Dormant Member
Join Date: Nov 2006
Location: Manchester, UK.
Posts: 157
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Re: Economy Variac. Is this a good idea?
And many lamp dimmers still arent inductive rated. Chinese variacs are not dear these days!!
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