producing heat (i.e. car cigarette lighter)

[tmp0]

Hello all,
This is my first post. I’m very new to electronics so bear with me, I’m doing my best.

I have a very small (10x10cm) metal plate, with so many little holes in it. I want this plate to heat up to a degree close to the cigarette lighter in a car. The metal plate is extremely thin.

I know that connecting a wire directly to a power supply (one end to positive and other to negative) produces heat. Should I try this with the metal plate or is that just crazy and dangerous?!

Any hints are highly appreciated.

Naimi

 

[mybuickskill6979]

i wouldn't put it on anything wooden! and i wouldn't advise holding it. how much power you putting to it? how much resistance does the plate have?

 

[Gaston]

you need to consider ohms law e=i*r. although a cigarette lighter has low resistance it still has more than a plate with holes in it. this is because the element is in a coil and that lengthens the path that the current has to flow. that combined with the material that it is made out of gives it some resistance to limmit the amount of current.puy your meter on the plate you have then plug the resistance into the equation with the voltage you plan to use and see what you come up with for current.

 

[HarveyH42]

I wouldn't use it in a 'water-pipe', touch a 9 volt battery to your tongue, you'll understand...

 

[Sceadwian]

You might end up creating more heat in the power supply than at the target.

 

[tmp0]

mybuickskill6979 & Gaston:
I currently have an adapter that outputs 12v DC and 2A.
The plate is not important, I can use any material, so what is the best resistance?

HarveyH42:
heh.. you cought me.

Sceadwian:
That doesn't sound good. How can I stop that from happening?

The adapter I have is taken from an old and broken harddisk case. Inputs 110v/220v AC, and outputs (as I mentioned before) 12v with 2A.

Thank you all for your time!

 

[Gaston]

well if you wanted to max out the output plug in the numbers. 12=2*r so 12/2=6 so 6 ohms of resistance would draw 2 amps at 12 volts. are you trying to make a heater or something? if you are trying to make a heater you could find an old toaster oven and series or parralle the elements to get 6 ohms.

 

[Hero999]

What are you trying to heat?

20W isn't a lot of power were heating is concerned.

 

[Sceadwian]

Keep in mind heaters heat relative to ambient, under the wrong conditions even a 'wimpy' 20 watt heater can be a fire risk. There needs to be some kind of thermal feedback, ususally it's pretty easy to just use a thermistor as close as possible to the heating element.

 

[Hero999]

That's true, a 20W soldering iron can be a fire risk!

Isn't is possible to use the heating element as a thermister?

If it's run from a regulated constant voltage then the current will alter depending on the temperature coefficient or the reisitive element.

 

[Sceadwian]

That would be difficult compared to just coupling a thermistor close to the heating element itself.

 

[ZIGGY_DAN]

That would be difficult compared to just coupling a thermistor close to the heating element itself.

That wouldn't be difficult, in fact it would be easier than using a thermistor because with the thermistor you would either need control circuitry or to use the thermistor in series but it would then dissapate some power, could you not simply use a car cigarette lighter?

 

[sam2]

They probably use the circuit you are looking for in the "vaporizer" deals they sell now.I dont mess with that stuff, but have seen them.
There is a fine line between getting enough heat in your screen/element to make it useable and melting it. sam

 

[sanjaysivakumar]

I had a similar requirement .I have to maintain a temperature of 70 degree on a metal piece 20x20 mm.What do i do.Which is a good material

 

[audioguru]

Hee, hee. This thread was dead for over 7 years and today it is reincarnated.

 

[Diver300]

I had a similar requirement .I have to maintain a temperature of 70 degree on a metal piece 20x20 mm.What do i do.Which is a good material

I suggest that you use a transistor of some sort as the heater. Power transistors are designed to be attached to heat sinks, so would be better for a 20 mm piece of metal than a resistor.

You will need a control circuit to stop it overheating and to limit the current when you turn on. On circuit is:-

**broken link removed**

That comes from this page **broken link removed** if you want an explanation of how it works. It is a heater for and ovened oscillator, so there is quite a lot about the oscillator, which probably won't be of interest.

 

[MrAl]

Hi,

I agree a power transistor could be used as the heating element for temperatures that are not too high. A power resistor really makes a good heater too though and the current and power are easy to calculate. The kind with the aluminum body makes a nice heater for temperatures under say 100 degrees C.
With a resistor the way to vary the heat is by the applied voltage, and with a bipolar transistor you could vary the base current too. In any case, the power supply has to be able to handle any power you need, and also the equivalent resistance that gets connected to it. Some power supplies will go into short circuit current limit if the resistance is too low even if the voltage is not that high yet.

 

[Diver300]

The big advantage of using a power transistor as a heater is that it is its own control device. While a small resistor may be needed to limit the current, the power in that will be small. Most circuits, such as **broken link removed** only have 0.6 V across the resistor at most.

If you have a resistor as the heating element, and you want to control the heating in a linear way, then you can easily end up with more heat in the control device than in the heating element, so you will need a heatsink for the control element.

You can, of course, use the heat from the control device to heat the item that the resistor is heating. Then you have, at least partially, ended up with the transistor as the heater.