230V to 110V converter

[gblades]

I have been reconditioning an old vintage Violet Ray device. It is all working fine but due to it's age it runs on 110V only so I would like to build a 230V converter for it with a built in fuse and switch.

I have been looking around at a few options. One is http://www.maplin.co.uk/p/240v-to-110v-300w-voltage-converter-vr05f but I don't know how it operates and whether it would really be suitable. I certainly don't want any form of switch mode system with a non sinusoidal output.

The other option is to just build something myself perhaps based around http://cpc.farnell.com/block/tim100/transformer-isolating-100va/dp/TF01494. Until now I have been testing it on a 110V 5KVA site transformer which is a little overkill.

Here is a diagram of the internals of a typical violet ray. They are rated at about 40W.
Any experience of the Maplin device or suggestions on another way to do it?

Thanks

[DmitryL]

Maplin's one has a dumb autotransformer in it.
Also, you can try searching cheaper alternative on ebay.

[MagicSmoker]

Interesting (quack) medical device there... As mentioned already, the simplest solution is a step-down autotransformer.

[Ian.M]

For powering something like that with dodgy vintage wiring and insulation, you really want an isolating transformer, not an autotransformer.  Just pick up a cheap site transformer and use it for any other 110-120V kit you acquire.  Its not like you will be putting this gadget into regular use, so why tie up funds for a dedicated supply?

[gblades]

Site transformers are way too big. Thanks for the information about the Maplin one being an autotransformer. So it looks like the isolating one from CPC would be the way to go.

[StillTrying]

I certainly don't want any form of switch mode system with a non sinusoidal output.

I don't think this thing is going to be too bothered by the shape of the waveform, in theory at least it would work with 50V DC.

[gblades]

I would like to keep the way it operates as original as possible. With it running off a sinusoidal waveform the output power would have a 50Hz component which would contribute to the noise they make. Running if off 50V DC for example might spoil that.

[StillTrying]

http://www.ebay.co.uk/itm/NEW-Mains-Isolation-Transformer-50VA-230V-PRI-24V-55-0-55V-SEC-CCM50-110-/351595613887

[Ian.M]

Did you spot the small 750VA site transformer from the same seller?
http://www.ebay.co.uk/itm/750VA-230V-Site-Tool-Transformer-16A-110V-Out-UK-Made-CM7501/351224863607
By the time you've bought a case for the bare transformer, and added a mains lead, circuit breaker and a socket for the 110V output, you could easily end up over the cost of the site transformer.

N.B. the site transformer will be CTE (centre tap earthed).  As this gadget is designed to emit a discharge from its electrode, it *MUST* be earth referenced.  If you connect it to a floating secondary on an ordinary isolation transformer,  the discharge could easily build up common mode DC voltage on the secondary until the transformer insulation breaks down.

[MagicSmoker]

For powering something like that with dodgy vintage wiring and insulation, you really want an isolating transformer, not an autotransformer.  Just pick up a cheap site transformer and use it for any other 110-120V kit you acquire.  Its not like you will be putting this gadget into regular use, so why tie up funds for a dedicated supply?

LOL at being safety conscious with a device that emits electromagnetic radiation from UV all the way up, potentially, to soft x-rays...

[Ian.M]

When operating as intended, it has a very low probability of killing you.  However if there is a crack in one of the insulators its a lot more risky so running it off a 55-0-55V supply minimises the risk of electrocution due to age related insulation failure.   The same principle goes for vintage live chassis TVs, Radios, Gramophones etc, where I strongly prefer to have a bit more insurance against electrocution, than some 60 year old beeswax packing over the recessed grub screw of a control knob.

[calexanian]

Ah, a good old handheld tesla coil. I actually just bought a new one recently. You may find it cheaper and easier to buy one ready made for your local voltage and style of plug needed. Here is a link to the company that makes them and the model I have.

http://www.electrotechnicproducts.com/bd-10a-high-frequency-generator] [url]http://www.electrotechnicproducts.com/bd-10a-high-frequency-generator[/url]

I find it very useful for checking for leaks in glass tubes, neon signs, fluorescent lights, and general mad scientist purposes. I recommend one of the new style ones. The vibrating reeds are far better now and the connection to the main tip is better. Also new ones will not give you the occasional arc through the body of the unit from breakdown of the old plastic. Fun for the whole family these things are! You can give yourself one heck of a shock though. I have done it accidentally and it is not fun.

[NiHaoMike]

For powering something like that with dodgy vintage wiring and insulation, you really want an isolating transformer, not an autotransformer.  Just pick up a cheap site transformer and use it for any other 110-120V kit you acquire.  Its not like you will be putting this gadget into regular use, so why tie up funds for a dedicated supply?

LOL at being safety conscious with a device that emits electromagnetic radiation from UV all the way up, potentially, to soft x-rays...

It would only generate X rays if applied to a device containing a vacuum.

Last time I have seen one of those devices being used was in a high school chemistry lab for sparking chemical reactions.

Perhaps the simplest solution would be a series cap or capacitive voltage divider? Since the device is inductive, beware that the required capacitance would be lower than what the current would suggest.

[macboy]

Your device contains some magnetics/transformers which may NOT be happy running on 50 Hz as opposed to the designed 60 Hz. You may get into saturation issues unless you also reduce the voltage by a 50/60 ratio.

[Seekonk]

I bet you could make that run off 24V DC power pack if you drove it with a 555 and a FET instead of that buzzer.  Wouldn't sound as good.

[crazyguy]

For powering something like that with dodgy vintage wiring and insulation, you really want an isolating transformer, not an autotransformer.  Just pick up a cheap site transformer and use it for any other 110-120V kit you acquire.  Its not like you will be putting this gadget into regular use, so why tie up funds for a dedicated supply?

LOL at being safety conscious with a device that emits electromagnetic radiation from UV all the way up, potentially, to soft x-rays...

It would only generate X rays if applied to a device containing a vacuum.

Last time I have seen one of those devices being used was in a high school chemistry lab for sparking chemical reactions.

Perhaps the simplest solution would be a series cap or capacitive voltage divider? Since the device is inductive, beware that the required capacitance would be lower than what the current would suggest.

It won't generate any x-ray, to generate x-ray it requires

(1) high voltage DC (30kV - 140kV) used to accelerate the electron
(2) vacuum tube
(3) a suitable anode target material such as Tungsten or  Molybdenum Target
(4) a filament (thermal electron emission)

The x-ray photon is generated by bremsstrahlung effect

[Wolfram]

For powering something like that with dodgy vintage wiring and insulation, you really want an isolating transformer, not an autotransformer.  Just pick up a cheap site transformer and use it for any other 110-120V kit you acquire.  Its not like you will be putting this gadget into regular use, so why tie up funds for a dedicated supply?

LOL at being safety conscious with a device that emits electromagnetic radiation from UV all the way up, potentially, to soft x-rays...

It would only generate X rays if applied to a device containing a vacuum.

Last time I have seen one of those devices being used was in a high school chemistry lab for sparking chemical reactions.

Perhaps the simplest solution would be a series cap or capacitive voltage divider? Since the device is inductive, beware that the required capacitance would be lower than what the current would suggest.

It won't generate any x-ray, to generate x-ray it requires

(1) high voltage DC (30kV - 140kV) used to accelerate the electron
(2) vacuum tube
(3) a suitable anode target material such as Tungsten or  Molybdenum Target
(4) a filament (thermal electron emission)

The x-ray photon is generated by bremsstrahlung effect

(1) X-rays can be produced by voltages as low as 100 V, but 1 mm glass will block most of the x-rays below 10 keV.

(2) X-rays can be produced in a tube with gas, as long as the gas pressure is low enough that electrons can accelerate to a high enough energy before hitting anything. This pressure is much lower than typically found in violet ray tubes though.

(3) Most materials will emit bremsstrahlung (and characteristic x-rays) when hit by an electron, molybdenum and tungsten are typically used because they have a high melting point (allowing a high power density and therefore a small focal spot for a given input power) and a high atomic number (giving high bremsstrahlung production efficiency).

(4) Most common x-ray tubes today are based on thermionic emission, but tubes based on gas breakdown and field emission also exist. Gas filled x-ray tubes were the only type in existence between 1895 and 1912, when the hot cathode tube was invented by Coolidge.