Power Supply for Cutting Foamed Polystyrene: Dimmer, 300W, 50Va Transformer, & Kanthal Wire 0.3

Question

Hello, this is my (I think) first post, also Hello to you very warmly. I am looking for advice about the power supply for cutting foamed polystyrene. I have: - dimmer up to 300W with built-in fuse - 50Va toroidal transformer - kenthal resistance wire 0.3 - some wires and plugs, crocodile clips,...

wojtek 9007 · Answer

Hello - will this thermal foam knife be for modeling or other purposes?
Will the resistance wire be stretched horizontally or vertically?
What is the power of the transformer - we know that the secondary voltage is 50V.

wenar · Answer

The wire will be horizontal. Yes for modeling purposes I bought two diodes and (red green) and 220 ohm resistors for the diodes

398216 Usunięty · Answer

Is the dimmer adapted to control the transformer's inductance? If not (usually dimmers are controlled by incandescent lighting) there may be a problem with the transformer - it may either burn after a while, or you will not get control.
Correct the first post - I understand that you gave the transformer power, not its voltage?

wenar · Answer

What regulator / dimmer could I use?

I don't know what to improve in the first post.

I'm not that familiar with the subject. It has a dimmer two outputs A1 and A2 and about inductance control and the first I hear.
I will use the whole power supply maybe 30 minutes a week

wojtek 9007 · Answer

The resistance wire you have (kanthal 0.3mm) its resistance is;
0.3mm = 19.1? / m.
You can unfasten this resistance wire for 1m test and connect it to the winding
17V secondary transformer.
The current that will flow will be within J = 0.9A.
You will assess whether this temperature is enough for cutting or if it is too low.

Added after 1 [minutes]:

Here is a table regarding resistance;
https://www.elektroda.pl/rtvforum/topic2362424.html

wenar · Answer

And what wire to use?
I'm talking about, for example, pulling a wire from an old hair dryer or something like that. or maybe there are other wires with lower resistance and this set that I have will handle it without burning or something else.
In general, I also mean reducing costs.

according to the table, I need about 42V to power the kentala
"The resultant resistance is close to 21 ohms. For a current of 2 A to flow through this wire, a voltage of 21 * 2 = 42 [V] must be applied to it."

wojtek 9007 · Answer

Hello - maybe write what wires you have (what diameter)?

wenar · Answer

I only have the one I mentioned ...
kenthal 0.3mm
but my fiancee mentioned something that her dryer broke and probably landed in the attic for "archiving" (you never know what element from such equipment will be useful

) (but it's not certain - you would have to check it out at the earliest at the weekend)

in addition, I will just get a dimmer from a strego oil heater.
will this be better? (this one in my room has a built-in fuse, the one in the radiator has no fuse)

and another issue:
I want to use two fuses. one on the secondary side one on the primary side. plus grounding (metal box after the computer power supply, grounding plugged into the casing plus where else to connect such grounding.?)

cirrostrato · Answer

The resistance wires at auctions are from the metro and cheap, you must use NEW because they are simple (no unwinding from spirals), the wire gets hot, so the necessary constant (even simple, spring) tension is extended, cantal wire I cut several dozen cubic meters of polystyrene 50mm, wire length approx. 30cm, power supply approx. 7V (I practically selected 15V / 40W pre-fed power supply from autotraf only for tests, then I used the same transformer with the appropriate voltage, after tests, I simply unwound part of the winding). I turned on (foot switch) only for the time of cutting and the wire (I also gave 0.3mm because I had it on hand) overheated (cracked) every 3 hours, 0.3mm wire may be too thin for cutting styrofoam 1m wide, I estimate the wire heating voltage 0.3mm / 1m at about 25V, so safety is guaranteed. Good advice: any practice in the subject will give you more than further hammering, e.g. thicker wire will give you (also tried) less precise cutting, too low temperature causes the styrofoam to stick again, too high kerf and burning the edges of the foam . Good luck.

wojtek 9007 · Answer

Write what the cutting length will be (wire length).

cirrostrato · Answer

The next (second) question to which the author of the topic gave the answer at the beginning, maybe it is worth reading from the beginning before asking ......

wenar · Answer

horizontally to modeling wing profiles Unfortunately, I know this theory, the frame is ready and the extraction also. probably you have to go to the tests, although I would like to mount at least one fuse, I just don't know which and where: /

Anonymous · Answer

If you have a regular regulator with a triac for 230V ~ then it should be connected on the secondary side of the transformer. Reduce the resistor, the value of the potentiometer, the RC system controlling the triac gate by the DB3 diac. Adjustment on the secondary side is not enough that it is better for trafo is even safer from the point of view of use. You don't have to worry about the maximum triac current. Usually triacs of the order of 8A and more are inserted.
When making wings or their forms, the temperature control of the wire by hand or foot on / off is not good.

wenar · Answer

The first part of the post was understood (removed from the quote). I don't understand the parts cited. I understand that the system has a built-in transformer, only the price is probably cosmic. And as for temperature control, for now I do not intend God knows what to do with this cut, the usual wing profiles. I have not yet grown up for assembling complex systems. Added 2 [hours] 22 [minutes]: This system connected to 230v burned the fuse into dimmers Fuse: F2AL250V.

Anonymous · Answer

The triac dimmer is phase controlled, i.e. you have a sine wave, more precisely one half of it. The triac is triggered by a DB3 diac with a trip voltage of 32V. To make it possible to delay relative to the moment when the mains voltage rises to 32V, it is necessary to add an RC delay system. R is adjustable, potentiometer. When the voltage from RC is applied to the diac, depending on the settings on the potentiometer, the moment of diac activation and thus switching on the triac will be delayed relative to that if the diac was connected directly. This is how the dimmer control works. You control the delay of switching on the triac. The later, the smaller the half of the sine wave will be led through the triac. If you change the supply voltage of the dimmer and it will be for example 50V, you should also change the resistor or capacitor of the RC system so as to reduce its time constant by which you adapt the system to new conditions, operating voltage.
The Triac can work equally well on the secondary side of trafo, i.e. where it is 50V. In 24V soldering tips, the triac is responsible for the heater current regulation.
You have in the system a secondary (low voltage) trafo winding, its first terminal - lead out, a triac with a regulator, a resistance wire or a heater and a second terminal of the secondary winding.
A typical 8A triac can handle 2.5A that will flow through 21R wire at a voltage of 50V.

wenar · Answer

If he understands well.
This:
1. toroidal transformer connect directly to 230VA
2. And this wall dimmer on one outlet cable

??

Deffectly regulate the currents on the secondary and not primary. (I was thinking about it with computer power supplies but it was discouraged because of other frequencies)

No more fuse for the dimmer, nothing else will test today. I will buy this fuse tomorrow.

Unless there is another option to play resistance wire safely.

Added after 4 [minutes]:

My woman just asked me the question, would you like yellow wires to enter the trafo? All in all, I doubted myself ...

Added after 26 [minutes]:

In the attachment the diagram I used.

tapio · Answer

Hello, I am going to make a machine for cutting foamed polystyrene. I will cut sheets of polystyrene with a thickness of 5cm up to 20cm mainly along the length (building insulation). I have a 20V 90W laptop power supply. Can you do something like that? And the question is what resistance wire should be used? I know that Kanthal wire but what thickness? The assumption is that it will cut 100cm sheets, i.e. the wire itself will be about 120cm long,

Power Supply for Cutting Foamed Polystyrene: Dimmer, 300W, 50Va Transformer, & Kanthal Wire 0.3

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