Hi,
I bought a $3.5 Chinese iron, exact power measured is 53watts. When I turned ON, it becomes so hot. When I turned off the room light, I can see the iron being red/orange color in dark room. I think it's horriable heat in the iron. 5 minutes heating turned the shiny body into blue-purple color. What you think? Please!

 

110V used with 220V?

 

Nepal uses 230V type C/D plugs,,, bet your iron is a chepo 120V one, which means the wattage is Four times thats 212W!!

 

Hi,
your ac line inputs is 110vac or 220vac. If the voltage is right according to the soldering iron specs.

The problem is thermostat of that iron. Secondly ,if that colored is not blown the heater itself its normal.

 

$3.50...says it all.

 

$3.5 iron sounds an standard iron for Nepal. From 10 years I was using $0.5 iron. From 3 years I am using $1 iron. So I decided to use a better one.

Mains in Nepal has 230V line. Also the iron label has 220/230V 60W. I felt the heating is little high because the iron tip also looks orange in dark room.

 

hi Willen,
Try this, allow the iron to reach 'red' heat, unplug it and quickly measure the resistance between Line and Neutral of the iron.
You can calc the wattage from these values.?
Try also when cold, just for reference.
E

 

It may be totally normal for non-temperature controlled dirt cheap 220V iron run at 220v in a dark room to have a glow to it..
Its probably running 900+ deg F/480+C an as such a glow would be entirely possible in the dark..

Note: its not going to make a good lightbulb so get out of the dark room and actually use it for soldering..

 

Before heating, its resistance is 930 ohms and when heated its resistance is 960 ohms. No more difference.

I think it's not normal heat because the tip and body became totally 'metallic blue' due to overheat. I never seen such burning metal color in soldering irons. Total iron turning ON time is 10 minutes till now. It seems that it will damage PCB traces due to excess heat while soldering. I am sure, It's not normal!

My $1 iron has a series diode inside. Some said it's because the heating element has been designed for 110V countries and sold to 220V countries with a series diode. So I guess the iron (being overheat) maybe missing a series diode. Do I need to try a 1N4007 series diode? Any problem?

 

220^2/960 = 50W

Its totally normal for a non-temperature controlled iron (or a temp controlled thats been turned up to 11) to be "metallic blue"/glowing in the dark..

Now it takes more "skill" to avoid burning/lifting pads,etc.. but entirely possible..

 

hi W,
I would try a 1N4007 diode in series with say the Line wire.
Lets know the result.
E

 

As 'mcgyvr' calculated it seems theoretically good, however when I was removing a component from PCB, the joint abnormally making 'pit pit pit' sounds, and melting was too quick.

I will add a series diode (with its heating coil) and see how heat I get.

 

If you add the series diode your wattage will drop to 12.5W,... You're better off using a simple light dimmer, and adjust it to your needs.

W= VxV /R

 

As 'mcgyvr' calculated it seems theoretically good, however when I was removing a component from PCB, the joint abnormally making 'pit pit pit' sounds, and melting was too quick.

100% To be expected with a non-temperature controlled iron.. At those temps you also have much shorter tip life/black tip disease from overheated flux,etc...
Its junk.. Expect junk..

 

Hi Willen

Also the iron label has 220/230V 60W

That 60 Watts is pretty high for a simple soldering pencil. I can do most general work using a 15 watt / 30 watt pencil. You may want to use the old trick of using a lamp dimmer with it to lower and control the heat.

Ron

 

Hi,
Dodgydave was saying the iron with diode dissipate Just around 12.5 W. I used a diode though and it seems I fixed the problem. Heating is in good level. Can solder little thick joints too, within few seconds. I think they forgot to add the diode. If I need different kinds of temperature level then I will use a dimmer.

How to calculate wattage if it has a series diode?

 

How to calculate wattage if it has a series diode?

If the element doesn't change much with temperature then the diode will reduce the wattage by about 1/2.
Basically the element is just seeing half the cycles.

Certainly glowing orange in the dark is way too hot for a soldering iron.
According to this, it means the iron was running around a 1000°C. That's more like a brazing temperature.

 

If the element doesn't change much with temperature then the diode will reduce the wattage by about 1/2.
Basically the element is just seeing half the cycles.

Certainly glowing orange in the dark is way too hot for a soldering iron.
According to this, it means the iron was running around a 1000°C. That's more like a brazing temperature.

Wattage will be reduced by a Quarter of the original as the Voltage is Halved!!

W=VxV /R

I think you meant to say the Diode will reduce the Voltage by half.!!

 

How to calculate wattage if it has a series diode?

When you feed a load with half a sinewave the RMS voltage drops to 1/√2 the RMS of the full sinewave, so with a resistive load the power drops to about .707 x .707 = 50%

 

Hello,

To complete the answer of @vrainom is here a table with rms values:



The power will drop to about 50 % as it is squared the voltage and not the 70 % he mentions.

Bertus