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ATX PSUI shorting out Answered

​Hi everyone, I hope I did this well, first time on this site, this is a question.
I want to make my own soldering iron/heating element, I know I can buy them but it is a project of mine and
I just want to know how it works and make it.


I used to power a copper wire with a 5V ATX PSU at 16Amps, the psu shorted out and stopped. I read somewhere that you can prevent the PSU from shorting out when there is enough resistance on the wire so the current is not too high for the PSU. (Total nitwit on electronics btw)
I was wondering if this is true, and how can I build a succesful soldering iron with a PSU, what transistor or what modifications to make.

Also, would a longer wire/rod produce more heat than a shorter? red hot would be nice.


Thanks in advance!

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nazmo76
nazmo76

5 years ago

If you want to calculate the resistance needed for your heating resistor, use Ohm's law:

Voltage(U)/Resistance(R) = Intensity(I) then:

Intensity(I)*Voltage(U) = Power(P)

U is in Volts

R is in Ωhms

I is in Amps

P is in Watts

so for 5V and 40W needed power (8A at 5V):

5/0.625=8*5=40W

8Amps is far below your 16 Amp limit, so at the same Voltage, you could use a twice as low resistance wire (0.3125Ω) so twice as much power but

always keep below the max of your machine, and 8Amp (40W) is fairly decent power for soldering.

Now, the difficult part is to find a way for you to get something working, no ideas here as I always bought pre made heating elements...

I was thinking of enamelled wire but it is not proper for your usage (too hot, the coating rosin will melt), as Downunder35m said: = you are best using nichrome wire or something like that.

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JStuyfzand
JStuyfzand

Reply 5 years ago

Thanks! This is helpful!

Instead of nichrome wire I tried using a graphite rod since I didn't have nichrome at the time, it worked great!

Wen I attach the negative charged solder it heads up red hot and melts the solder almost instantly!

I might do an I'ble on it

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Downunder35m
Downunder35m

Reply 5 years ago

Be aware though that not all graphite rods / pencils are usable for this!
For example rods from old D cell batteries work great while a carpenters pencil literally explodes into a lot of glowing hot pieces.
If you make an Ible about it check some materials first and leave a proper warning note about types of graphite that can't be used.

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JStuyfzand
JStuyfzand

Reply 5 years ago

I had one explode in my face yesterday, nothing happened though.

What do you think is the best type of pencil lead for this?

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Downunder35m
Downunder35m

Reply 5 years ago

The best type would be made from Nichrome or Kaptan wire - as I said graphite is not really suitable for your project.
You were lucky one - how many time can you be lucky before the house burns down ? ;)

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JStuyfzand
JStuyfzand

Reply 5 years ago

Hahaha, I am buying kanthal wire soon for electric furnace, lets make a soldering iron too! :)

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nazmo76
nazmo76

Reply 5 years ago

I'm happy if I helped you.

As heating wire, those stainless steel brushes to clean dishes are great but they might break as tin does.

To obtain usable material, just pull a string of steel from the ball and eventually it will break, leaving some length of conductive wire...

For the Instructable, please do ! That could be fun

Finally, if you want to build something cool, you can go for an intensity regulated PSU that will enable you to controll the heating of your iron

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JStuyfzand
JStuyfzand

Reply 5 years ago

I will try the brush, but does steel have enough resistance? I heard that it is something like copper wire.

The PSU oart sounds complicated, do you have an i'ble on it?

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nazmo76
nazmo76

Reply 5 years ago

If the length is high, the resistance will follow.

For the PSU, you can go simple and use an already built circuit, search "DC DC Buck converter" on ebay with the amps and voltages ranges you need,

you'll find a lot of them with prices starting at 1$, though, you want something with 2 potentiometers, so around 4-5$ will be good.

for i'bles, here is a compilation but search for ATX conversion and you'll find a lot of results:

https://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/

But if you go inside your PSU (you're not obligated to do this mod), be very careful with high voltages and capacitors that ca at least give you a good shock

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Downunder35m
Downunder35m

5 years ago

Copper is not used for heatin, that why we have heating wire in the form of Kanthal or Nichrome.
Resistance is given per meter, so go for a lenght that fits the bill.
Although for normal soldering 30W is enough, 100 for wood burning tasks....
And you will realise that the size shrinks dramatically when using the right wire.
Maybe it is worth looking into heater cartridges for 3D printers too to keep it simple?

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JStuyfzand
JStuyfzand

Reply 5 years ago

I tried a graphite pencil core while experimentig, well, it had resistance.

It it glowed white hot! So I have my soldering, but does more (longer core) resistance make fot more heat or the opposite?

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Downunder35m
Downunder35m

Reply 5 years ago

You fail to understand the how to.
It does not matter if copper or pencil - none of them are suitable.

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JStuyfzand
JStuyfzand

Reply 5 years ago

I used a pencil and it did not short out the PSU, it then proceeded to turn white hot.

I know it is not a proffesional grade but I can make it work for me, the copper wire did not work, thats for sure.

I will look into chromium later but for now a pencil lead will do.

Any thoughts?