Safety advices before experimenting with these circuits

[RODALCO]

Old CFL's are great for burning out on a MOT. They glow for a while and emits interesting smoke clouds.

 

[audioguru]

Why does it say "daylight"on the box for an LED light bulb or a CFL when the color is not white, it is blue?

 

[J_Nichols]

Yes if you put 12v 50-60hz on the secondary you'd get 240v on the primary, the regulation on a small trans would be poor, meaning the voltage would drop as soon as a load is connected, might be enough to drive a small fluorescent tube.
If you exceed the rated voltage primary or secondary the core would saturate, making the winding act more like a short circuit.

I made a different simple test and it hasn't worked.

I have a medium size toroidal core where I have wound 4 turns of wire. The purpose was to connect the coil as the primary winding. In the setup I have not used a secondary coil.
The problem has been when connecting it to the wall plug. There was something wrong because all the lights went out.
What I have done wrong?

 

[fezder]

You placed that as primary wiring to 230v side, and plugged that in photo in wall socket? Green wires were for primary)
If that's the case, Id say too much current and hence fuse blowed. Inrush current killed fuse.
And to my eye, such small wires look quite small for primary side in terms of insulation at least.

 

[fezder]

Nichols, the moment when you place wire to AC-voltage, only thing that resists current, is only wire's resistance. Inrush current can be calculated with ohms law. After the moment when AC voltage starts to effect, resistance is combination of ferrite core used, wires resistance as well as wires inductance (mainly from that "loop" you make around transformer core. Test that thing you build with smaller, safer voltage first, like transformer and with function generator to see how transformer behaves. (I simplified bit the start of this message, but main thing is seen)

Please don't put that thing on wall anymore, at least please cover it well enought so in case fuse is lazy and won't trip and that transformer wire acts as fuse, doens't catch fire and cause further harm. And primary side of transformer should always have fuse, wall fuse is not enough.

 

[dr pepper]

If your not experienced please do not play with wall sockets or the mains, you could hurt yourself, mains is extremely dangerous.

 

[fezder]

Indeed, mains voltage is very lethal, not it feels awful (well okay, I experienced only 120v....) but it can lead to burns, and possibly death through cardiac arrest in case mains current flows throught heart. (situation when heart pumps on mains frequency, 60hz) not to mention, you can't let go once you are hooked in mains voltage. You don't need to start fearing mains voltage, respect it and know what you really are doing.

 

[J_Nichols]

You placed that as primary wiring to 230v side, and plugged that in photo in wall socket? Green wires were for primary)
If that's the case, Id say too much current and hence fuse blowed. Inrush current killed fuse.
And to my eye, such small wires look quite small for primary side in terms of insulation at least.

Yes, I used the green wires as the primary and connected them to the wall socket.
I will try to use 12 volts AC 0.3 amperes and see if happens the same. I have a transformer to step down 230 VAC to 12 VAC and the current output is 0.3 amperes, so using the output of the step down transformer as the primary energy source to feed the same toroid transformer, it should work. Right?

 

[J_Nichols]

Indeed, mains voltage is very lethal, not it feels awful (well okay, I experienced only 120v....) but it can lead to burns, and possibly death through cardiac arrest in case mains current flows throught heart. (situation when heart pumps on mains frequency, 60hz) not to mention, you can't let go once you are hooked in mains voltage. You don't need to start fearing mains voltage, respect it and know what you really are doing.

Of course, I will ask every single details before doing anything. Thank you for the advice.

 

[fezder]

I will try to use 12 volts AC 0.3 amperes and see if happens the same. I have a transformer to step down 230 VAC to 12 VAC and the current output is 0.3 amperes, so using the output of the step down transformer as the primary energy source to feed the same toroid transformer, it should work. Right?

Sounds MUCH more safer . I fear however that it causes too much load on transformer, you can attach as low as: ohms=volts/amperes->12v/0.3A=40ohms. (But, actual voltage can be as high as 1.414, or square of 2, times voltage,=1.414 x 12volts~16volts, but this was just an extra stuff here) Also, when transformer is unloaded, voltage on secondary is higher than what is said. The values you see are constant ratings, but it is not wise to keep load on maxinum)

What equipment do you have?

 

[fezder]

Read this , good stuff:
**broken link removed**

 

[fezder]

And since we're dealing with inductive resistance, what is your base of knowledge? (resistances are msinly divided in 3; resistive, purely resistive, like resistor, inductive, more inductive, like coil/transformer, and capacitive, like capacitor) Each behaves differently in ac/dc, except resistive, which is "same" all time.

 

[RODALCO]

The toroid material is designed for high frequencies, not ideal for a mains 50 or 60 Hz transformer, which have a laminated steel core. The four turns on your toroid would be a dead short and take out the circuit breaker.

 

[RODALCO]

And since we're dealing with inductive resistance, what is your base of knowledge? (resistances are msinly divided in 3; resistive, purely resistive, like resistor, inductive, more inductive, like coil/transformer, and capacitive, like capacitor) Each behaves differently in ac/dc, except resistive, which is "same" all time.

True.
Inductive resistance is interesting and people need to understand how to correctly measure them.

For example:
The primary winding (DC resistance) of a 100 kVA distribution TX is 16 Ohms. This is connected to 11,000 Volts.
A 500 VA washing machine motor may measure 55 Ohms and is connected to a 240 Volts supply.

 

[audioguru]

Good grief!! 230VAC/50Hz on only 4 turns of wire on a ferrite core?? That is a short circuit almost the same as plugging in a paper clip.
Did it make a loud buzz before the lights went out?

 

[spec]

Hi J Nichols,

I can find no information about your location so I can't establish the exact characteristics of your mains supply, but as it is 240V I am assuming that it is three wire: Live, Neutral and Earth

In addition to the safety warnings/measures that the other members have said you should do three more things:
(1) Put a low value fuse (300mA to 500ma say) in the plug that feeds the mains to your transformer
(2) Make sure that the an earth trip is in the mains supply circuit.
(3) Connect the earth wire from the mains cable to the body of the transformer.

A bit more about transformers:

(1) The primary of a transformer looks like an inductor to the mains supply.
(2) The inductance depends on the transformer dimensions and core material.
(3) The inductance is also proportional to the number of turns squared of wire wound around the core.
(4) An inductor resists alternating current. The higher the inductance the higher the reactance (= resistance)
(5) Depending on its size, a transformer can only support a certain magnetizing force = no of amps * number of turns of wire.
(6) If the magnatizing force is too great the core will saturate and there will no longer be any inductance to resist the current from the mains supply. As has already been said, the only thing that will resist the current is the resistance of the wire, which wont be much. Consequently a huge current will flow and if a fuse does not blow, which it should, the wire will get so hot that it will go open circuit. Under certain circumstances and with certain transformers there could be a fire and even an explosion.

In the case of your transformer I would expect there to be 20 turns on the primary for every 1V of AC input voltage so the primary would consist or 240V * 20 turns = 4,800 turns.

On the other hand a big transformer, say weighing 10 lbs, would have only one turn per volt.

In case you are interested the reactance (resistance) of an inductor is 2* pi * F * L Ohms.
Where:
F= frequency
L= inductance in Henrys



It has already been explained why your toroidal inductor would not be suitable for connecting to the mains supply: not enough turns and a core that does not generate much inductance anyway.

As you know, and as the other members have emphasized mains voltages are dangerous and mains transformers especially so. On no account touch the transformer if the plug supplying the mains supply is plugged into the mains supply socket.

Quite honestly, you would be much better off leaving any mains voltage experiments for a while and only experiment with AC voltages of 30V maximum and 50V DC maximum.

spec

 

[fezder]

Spec, I was waiting for your post on this topic, had this feeling you'd join too. Phew, you really put effort on your posts

 

[J_Nichols]

Sounds MUCH more safer . I fear however that it causes too much load on transformer, you can attach as low as: ohms=volts/amperes->12v/0.3A=40ohms. (But, actual voltage can be as high as 1.414, or square of 2, times voltage,=1.414 x 12volts~16volts, but this was just an extra stuff here) Also, when transformer is unloaded, voltage on secondary is higher than what is said. The values you see are constant ratings, but it is not wise to keep load on maxinum)

What equipment do you have?

Yes, of course. I didn't know that the setup would cause problems.
Very interesting information, I am also reading the link you have posted some posts after this one.

The equipment I have is very basic: a multimeter and a clamp meter. Nothing more.

 

[J_Nichols]

The toroid material is designed for high frequencies, not ideal for a mains 50 or 60 Hz transformer, which have a laminated steel core. The four turns on your toroid would be a dead short and take out the circuit breaker.

I have a small transformer with a laminated steel core. The configuration was similar to the setup I was trying, so I thought that using the toroid core would be very similar. But no.

The laminated steel core is a soft magnetic core?

 

[fezder]

The knowledge as well as equipment we all start is basic; ones interests and needs fill the gaps. However, multimeter will take you far, and clamp meter is nice bonus. Also, many clamp meters have voltage reading. Personally I was lucky to get good entry gear, but what I'd suggest when playing with ac voltage, is oscilloscope. Multimeter won't tell real deal about ac-voltage....but, oscilloscope is perhaps the most dangerous measuring equipment in lab, but indisbensable once you get your hands on one. Any cheapo will do, 20MHZ analog scope, they are very cheap when bought as used. And then there's hand-held 'scopes, but I don't have experience of them, read too many reviefs.....
IF you get your hands on scope, ask around here to get good info how to use it, I use it pretty much daily...