What type of wire is this?

[Overclocked]

I recently aquired a grill cheese making machine. I took it apart (yes it still works) and I found this wire inside wrapped around. Im assuming its the heater.

But what type of wire is it? It looks like the kind thats in your toaster ( i think its called neochrome wire but I cant find any info on it..)

It grilled cheese making machine hooks up directly to AC, and there where 2 coils in series.

 

[audioguru]

If you spell Nichrome correctly, a search on Google is much easier.
https://www.google.com/search?hl=en&q=nichrome+wire

 

[theinfamousbob]

now im going out on a limb here (havent researched it at all) but wouldnt it be a high-resistance metal? after all, resistance generates heat. look at your oven...

 

[Overclocked]

Does nichrome wire work with DC too? If so thats great! then I dont have to risk getting shocked!

Of course I do have a viarac which can provide up to 3 Amps..

 

[Roff]

now im going out on a limb here (havent researched it at all) but wouldnt it be a high-resistance metal? after all, resistance generates heat. look at your oven...

It is resistance wire, but power is only proportional to resistance if your supply puts out constant current. In this case, Power=I^2*R.
However, constant current supplies are very unusual. The norm is constant voltage (as load varies), e.g, batteries, power mains, alternators, etc. Your oven runs off constant voltage, so P=V^2/R. This means that power is inversely proportional to resistance - as the resistance goes down, the power goes up.

 

[Roff]

Does nichrome wire work with DC too? If so thats great! then I dont have to risk getting shocked!

Of course I do have a viarac which can provide up to 3 Amps..

Don't think you can't get shocked with DC. If you apply enough DC to a toaster to heat it up (110V, in the US), it will shock you, and can kill you. See for more info on the dangers of AC and DC.

 

[Overclocked]

Well I meant being shocked By AC, If this fails on AC, then stuff could happen (fire) But could a fire break out? Or will the circuit breaker,break the circuit before something does happen?

I can provide 12V at what ever current this thing requires...

 

[audioguru]

With only 12V, a heater designed for 120V will barely get warm and use only 1/100th the power.

The 25,000 volts in your TV is DC, not AC and can kill you in an instant.

The 12V battery in a car is DC, and you can't feel it. If you put a resistance of 1000 ohms across it, the current will be only 0.012A and the resulting power of only 0.144W wouldn't cause much heat in the resistance. If you put a resistance of only 0.1 ohms across it, the current will be 120A and the resulting power of 1,440W will produce extreme heating of the resistance.

 

[Overclocked]

Just in case your wondering what Im doing, Im making a plexy bender ( I have some ideas)

This is what the whole thing (1 panel though) Looks like:
**broken link removed**

The wire is right under the covers.

Now to bend Plexy, Should I leave it the way it is? So the point where I want the plexy to bend will touch the metal (err sit on it) and heat it up just enough to be bent.

 

[Nigel Goodwin]

The 25,000 volts in your TV is DC, not AC and can kill you in an instant.

The 25,000V in a TV is limited to only about 1mA, far too low to be fatal - however, the shock may make you fall over and break your neck :lol:

However, both AC and DC can kill you, with DC generally considered to be the more dangerous.

 

[pike]

The 25,000V in a TV is limited to only about 1mA, far too low to be fatal - however, the shock may make you fall over and break your neck :lol:

AHAHAHAH, thats the lamest way to die.

Microwaves though do however tell a different story.

 

[Nigel Goodwin]

The 25,000V in a TV is limited to only about 1mA, far too low to be fatal - however, the shock may make you fall over and break your neck :lol:

AHAHAHAH, thats the lamest way to die.

Microwaves though do however tell a different story.

Microwaves are FAR more seriously devices, they have 3000V DC at high current, almost certainly fatal - I don't know a single person who's ever had a shock off one!. I know hundreds of people who've had multiple shocks off TV's (myself included!), it's a hazard of the job :lol:

I probably get a shock every couple of weeks?, varying from 300V to 25KV - the most painful part is the burn you often get at the contact points :lol:

Old TV engineers trick! - NEVER grab anything metal, always stroke it with the back of your fingers first - that way you can't possibly get a grab reflex on it!. Also, if it's live, it feels rough as you stroke it.

I did hear of a guy not far away who did get shocked from a microwave, he was EXTREMELY lucky, paramedics just happened to be two doors away and they were there in a matter of seconds. By applying CPR they managed to bring him back to life, although I did hear he's never been quite right since :cry:

 

[audioguru]

The 25,000V in a TV is limited to only about 1mA, far too low to be fatal.

My 32" Sony colour TV seems to light-up my whole large room with about 100W of light, so the current must be at least 4mA. I have heard that the HV in a large colour TV is "stiff" and fairly regulated so when it shocks you its current instantly increases. When souping-up my old TV I never got shocked because I stayed away from its HV.

 

[Nigel Goodwin]

The 25,000V in a TV is limited to only about 1mA, far too low to be fatal.

My 32" Sony colour TV seems to light-up my whole large room with about 100W of light, so the current must be at least 4mA.

Just checked the spec for a KV32HX15U (32 inch Sony TV), it's total power consumption is only 75W according to both the specification and the service manual (the 28 inch version is 72W).

So EHT is presumably limited to around 1mA?, as it's always been since the early days of colour TV.

BTW, a 32 inch TV will have higher EHT than 25KV, but the manual doesn't specify what it is.

I have heard that the HV in a large colour TV is "stiff" and fairly regulated so when it shocks you its current instantly increases. When souping-up my old TV I never got shocked because I stayed away from its HV.

No, EHT isn't highly regulated, just the opposite, it's current limited. The current drawn by the line output stage is monitored (it's called beam current limiting), if the beam current exceeds 1mA then the contrast is reduced. If this doesn't drop the beam current enough then the set will be shut down.

There's also over voltage protection on the tube as well, if the EHT rises excessively then the set will shut down, in Japanese sets this is called "X-ray protection" - because excessive EHT can cause a CRT to emit X-rays, which is basically how they are generated in X-ray machines.

 

[audioguru]

Thanks for the good info, Nigel.
I hope we don't get some nubees poking around inside their powered colour TVs. If the EHV won't kill them then the mains or the TV's weight will.

 

[Overclocked]

Could I use this circuit to control temps?

**broken link removed**

 

[audioguru]

That's what it is for. Perfect!

 

[Oznog]

A machine entirely for making grilled cheese sandwiches? Brilliant! I love grilled cheese yet could never find time for the tedious minutes it takes to do the grilling.

Mmmm... grilled cheese.

 

[Overclocked]

For now, Could I use the viarac to control the Voltage for experimentation?

I have a 50ohm, 50W pot (1 amp max..)

 

[Klaus]

Just in case your wondering what Im doing, Im making a plexy bender ( I have some ideas)

This is what the whole thing (1 panel though) Looks like:
**broken link removed**

The wire is right under the covers.

Now to bend Plexy, Should I leave it the way it is? So the point where I want the plexy to bend will touch the metal (err sit on it) and heat it up just enough to be bent.

Everybody else seems to have got side tracked with electric shock stories :shock:, meanwhile your plexi bender idea got ignored.

It appears you want to bend the plexiglass into a dish shape, right?
Are you planning to push it down with a matching tool pad once it is soft?
If so then your idea might not work as it only heats the perimeter of the plexiglass.
If I was to do this I would make a male and female former without a heater. I would heat the flat plexiglass sheet in the kitchen oven, which has a nice temperature control for the job. Then its just a matter to place the soft sheet over the female former and press down & clamp the male plug.
If you want a really fancy method, suitable for repeated moulds, then make a vacuum former. Its an air tight shallow tray with a air tight fitting lid frame and a rubber membrane. You place a male former in the bottom of the tray. You put the hot perspex on it, close & clamp the lid shut and apply the vacuum. The rubber membrane waps itself tightly over the male former, taking the pliable perspex with it. You can shape fairly comples forms that way.

have fun experimenting,

Klaus