Soldering iron improvement mods

[VK3DRB]

I own a few soldering irons. One of them is a Weller with a Curie temperature switch I bought in 1980, model TC202D. Still going strong, although I tend to use it when I am off site. This iron was proudly MADE IN AUSTRALIA (Albury, NSW).

Here are two mods I did years ago that have served to be very useful:

(1) You can solder devices that have voltage on them that would normally have a path to earth (DC or AC). That is, there is voltage on them. I had to do this on occasions, either through laziness, time constraints or when capacitors might still have charge in them. I am not talking mains here, but SELV voltages! Usually soldering irons are earthed and touching the live component can sometimes have negative consequences (to the circuit or your iron) The mod is to insert a switch on the case of the soldering iron box to connect of disconnect the earth, depending upon what you are doing.

(2) Back in 1981,  a lecturer at RMIT once built a 6 transistor circuit to switch on a LED on his Weller when the transformer secondary AC voltage had increased slightly, meaning "I have reached temperature". That is, the AC voltage dropped when the iron was heating up. I came up with another solution, to which the lecturer was impressed by its sheer simplicity. Put a series low ohms resistor in line with the transformer secondary and as the iron is heating, an AC voltage is developed across the resistor. Use another resistor in series with an LED across that low ohms resistor and the LED turns on when heating and turns off when it is heated. Works a treat!

For him: Weller products.
For her: Wella products.

Anyone else have hints and tricks for common tools, like soldering irons?

[Wh1sper]

(2)  Put a series low ohms resistor in line with the transformer secondary and as the iron is heating, an AC voltage is developed across the resistor. Use another resistor in series with an LED across that low ohms resistor and the LED turns on when heating and turns off when it is heated. Works a treat!

I've had done this also, the gear still works for my son.

For him: Weller products.
For her: Wella products.

Cool.

[richard.cs]

I came up with another solution, to which the lecturer was impressed by its sheer simplicity. Put a series low ohms resistor in line with the transformer secondary and as the iron is heating, an AC voltage is developed across the resistor. Use another resistor in series with an LED across that low ohms resistor and the LED turns on when heating and turns off when it is heated. Works a treat!

I would be inclined to do this with a current transformer to reduce the wasted power, the resistor design drops over two volts at a couple of amps (so for a 60W 24V iron the resistor has to dissipate about 5 Watts). Take the smallest mains transformer you can find, probably a little PCB-mounted thing or something from a wallwart - these are usually 10-15 turns per volt. Strip off the primary leaving just the secondary which for a 12V transformer might be 150 turns. Pass a single turn of the heating current through the core and wire an LED and an antiparallel diode across the secondary. For a 2A rms primary current the LED will get 0.5*(2000 mA)/150 = 7 mA rms (it's only on half-wave) but the voltaage reflected across the single turn primary will only be (2.5 V)/150 = 17 mV.

On the other hand the Weller irons produce a loud click when they're at temperature and a spike that's visible on all the test gear in the lab so maybe it's not really needed. 

[VK3DRB]

I came up with another solution, to which the lecturer was impressed by its sheer simplicity. Put a series low ohms resistor in line with the transformer secondary and as the iron is heating, an AC voltage is developed across the resistor. Use another resistor in series with an LED across that low ohms resistor and the LED turns on when heating and turns off when it is heated. Works a treat!

I would be inclined to do this with a current transformer to reduce the wasted power, the resistor design drops over two volts at a couple of amps (so for a 60W 24V iron the resistor has to dissipate about 5 Watts). Take the smallest mains transformer you can find, probably a little PCB-mounted thing or something from a wallwart - these are usually 10-15 turns per volt. Strip off the primary leaving just the secondary which for a 12V transformer might be 150 turns. Pass a single turn of the heating current through the core and wire an LED and an antiparallel diode across the secondary. For a 2A rms primary current the LED will get 0.5*(2000 mA)/150 = 7 mA rms (it's only on half-wave) but the voltaage reflected across the single turn primary will only be (2.5 V)/150 = 17 mV.

On the other hand the Weller irons produce a loud click when they're at temperature and a spike that's visible on all the test gear in the lab so maybe it's not really needed. 

That is even a better idea - most efficient. However I found no detrimental effect on the soldering with the small voltage drop. As for wasting power (heat in the resistor), in years gone by it was not considered, but these days with our government having sold off the peoples' electricity supply to mostly foreign owned private enterprise , our electricity costs have sky-rocketed so energy savings is always on our minds these day.

[ruessel]

Hello,

simply connect a LED in series with a resistor across the curie microswitch in the magnastat iron. The LED lights when the iron has reached its temperature, goes off, when iron is heated up.
Simple mod, LED is in the handpiece no waste of energy.

Helmut

[richard.cs]

Hello,

simply connect a LED in series with a resistor across the curie microswitch in the magnastat iron. The LED lights when the iron has reached its temperature, goes off, when iron is heated up.
Simple mod, LED is in the handpiece no waste of energy.

Helmut

Nice and simple, I like it :-)