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Deception In Soldering Iron Ratings

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by MrAl, Dec 3, 2014.

  1. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Hey want this thread a sticky the other day? What happened?
     
  2. Inquisitive

    Inquisitive Super Moderator

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    Done.
     
  3. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Oh great. I was hoping others could see the info and then buy with more discretion.
    I also made a typo, it should have read "Hey wasn't this thread a sticky the other day ?" ha ha.
     
  4. dave

    Dave New Member

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  5. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello again,

    I have some new information to add to the thread.

    First, it looks like the heating element for the major soldering irons that go with a lot of stations is the A1321 or A1322, and it appears that they may be the same. It also appears that there are two totally different physical models but they may call BOTH models (even though very different electrically) by the same part number like those above.

    They both have one heating element and one sensor but for example, it looks like the A1321 can be either heating element and sensor.
    I'll list the elements and sensors first (cold=20 degrees C or room temperature):

    Heating elements:
    1. 16 ohms cold
    2. 4 ohms cold

    Sensors:
    1. 1.5 ohms cold
    2. 50 ohms cold

    Each soldering element has one sensor and one heating element, and what i have found so far is that they pair up as:
    Element A: 16 ohms heating element, 1.5 ohms sensor
    Element B: 4 ohms heating element, 50 ohms sensor

    Unfortunately they are both marketed as A1321 for example.

    The soldering irons purchased as a whole (handle + element already installed) seem to come in several types, the most common seem to be:
    1. 907A (36 watts)
    2. 907F (50 watts)

    It looks like the 907A has the 16 ohm element and 1.5 ohm sensor, while the 907F has the 4 ohm element and 50 ohm sensor.

    The irons are different because of the power they run at, either 50 watts (907F) or 36 watts (907A) and that is because of the heating element coil type. The station that uses these irons seem to be matched to a particular model, either 907A or 907F and it looks like the stations can not run with the wrong type because the element is too different for one thing.

    The element in the 907A is 36 watts and has a K type THERMOCOUPLE sensor, so the station circuit relies on measuring a VOLTAGE in order to determine the element temperature.
    The element in the 907F is 50 watts and has a PTC type THERMISTOR sensor, so the station relies on measuring a RESISTANCE in order to determine the element temperature.

    The two different station circuits can not function with the wrong iron because they simply can not measure the temperature properly, and also the required power handling is higher for the 907F so it could even blow the station out.

    Control circuits for these two irons are very easy to build however. It's just a regulator that uses the sensor as feedback and compares it to a pot setting. When the measured quantity equals the pot setting the iron current is shut off.

    For some reason the stations use AC not DC, although the elements are rated for DC. I suspect this is only because it is easier to use a triac with simple control circuit to turn the iron element on and off (and thus vary the average power to the iron) rather than have to use a DC power supply in addition to the control circuit and power transistor.

    There seems to be a lot of other different types of irons used with other stations, but these two are very common. The problem is purchasing an element because it's hard to tell what we might get, 50 watt with PTC thermistor or 36 watt with K-thermocouple.
    The irons themselves however seem to be consistent so that the 907A should always be the same (36 watt) and the 907F always the same (50 watt), so it is probably better to purchase the whole iron as a replacement.

    Interestingly, we can get the 907A irons for about 10 dollars USD, and the 907F for about 15 dollars USD, so a small control circuit with it will give us a nice temperature controlled soldering station :)
    If you have a DC power supply that can put out 2 to 2.5 amps, you can run either iron with a small LM358 based control circuit and have yourself a $50 USD soldering iron station. This would be without a 7 segment LED display to show the temperature, but that's not really needed anyway if you calibrate the pot dial. With a simple arduino circuit the display can be added too.
     
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  6. throbscottle

    throbscottle Well-Known Member

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  7. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Well actually people might want to build their own so a link to a controller isnt a bad idea i think, but there are going to be simpler ones that use common parts like the LM358 for example, and no microcontroller so no programming is necessary. But i couldnt find a link for the schematic for that one.

    I didnt mean to imply that we could not build one, just that i dont think there are any commercially made units that will work with both soldering iron types. This is probably because if they use the 907F then they assume you dont need to run the 907A because the 907F is higher powered and can be adjusted down as needed with the control. If it uses the 907A then that's because they wanted to cut cost to a minimum so they wont want to have to drive the 907F. My station came at a rock bottom price of $70 USD so it uses the 907A. I do want to mention that it does solder pretty well though even with that lower rated iron. I was even able to fix a pair of reading glasses which had a rather large area to be soldered. No problem with normal PC board connections either. Not the best iron but not the worst either :)
     
  8. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,

    A little more information on the soldering station input power.

    The station input power is around 30 watts even with nothing turned on, such as the soldering iron. This helps explain why it uses around 55 watts with the soldering iron turned on when the iron itself only uses about 36 watts (16 ohms at 24 volts).

    I have yet to do a tear down but that's coming.
     
  9. Externet

    Externet Member

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    Hi gentlemen. It is interesting seeing this thread with no mention to temperatures, just wattage. Both should be considered.

    To melt a given solder, it is temperature what we should watch. To melt a small or a large solder blob (or small/large heat sinking piece) wattage is what we should watch. For repeated soldering, both and more should be considered.
    A 80W iron may not reach a desired temperature.
    A 15W iron may not reach a desired temperature.
    A 80W iron may overheat a joint.
    A 15W iron may overheat a joint.
    Judging an iron by its wattage does not determine its capability for satisfaction on all tasks.

    The proper use comes from skills and experience after understanding the different things 'heat' and 'temperature' are.
    ----> A match to light a cigarette, and a house on fire may be at about the same temperatures. But the amount of heat in them is very different <----
    Further, in the skills section, the wetness, shape, size/length of the tip and the item to solder plays also a role.

    The temperature an iron reaches can vary on factors as its thermal insulation, thermal conductivity of its materials/construction, ambient temperature, wind, time...
    Try to solder a RG-8 on a PL259 on the roof of a ship on a windy winter and you will find the same 60W iron that worked great indoors is garbage.

    The length from the heating element to the tip also affects its behavior. It may initially produce a proper joint, but the next one can fail as the tip drops temperature and there should be a wait time until the heat transfers and replenishes the tip raising its temperature to the desired level in order to continue.

    There is hidden factors in the art of proper soldering that are usually not considered, relying on the iron marketing specifications, fanatism for brands, and wrong expectations bringing deception.
     
    Last edited: Dec 26, 2014
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  10. tvtech

    tvtech Well-Known Member Most Helpful Member

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    I can see where you are coming from Externet

    Good for you explaining this :)

    Regards,
    tvtech
     
  11. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    I am sorry to say that i have to disagree entirely. This is mainly because when comparing irons for soldering we consider the wattage only, everything else we consider being equal.

    For example, when you want to light a cigarette you look for a match, and most matches do the same thing.
    When you want to solder, you look for a soldering iron, and most soldering irons get up to around the same temperature but the wattage is what allows us to solder a certain size joint. And the price goes roughly with the wattage so that a larger iron made by the same manufacturer in general cost more. If you can push a low wattage iron off as a high wattage iron you sell more.

    Also, the wattage in the case of the temperature controlled irion is even less important for overheating a joint because it will be temperature controlled. The size of the tip is what matters most here when the tip is temperature controlled.

    Look around on the web for various irons and see what the difference is. The low wattage ones are smaller and the big wattage one are bigger. Of course we dont need a 100 watt iron for a DIP ic package, but a 100 watt temperature controlled iron could solder a tiny IC pin just as well as a 20 watt iron, even though you might think at first that you should only use a 20 watt iron. That's because it is temperature controlled.
    So you see a 20 watt iron could solder a tiny IC pin, and so could a 100 watt temp controlled iron, but a 20 watt iron could not solder a heavy lug to a heavy gauge wire while a 100 watt iron can (ok might need 150 watts but you get the point).

    The point of cost is:
    The 100 watt will cost a lot more than the 20 watt iron, but if you can sell the 20 watt iron for the cost of a 100 watt iron then you can make more money by not being honest about the spec's.

    I will point out that we have to be careful when comparing costs too, because some real chip irons will cost less but they are not made as well.
     
  12. throbscottle

    throbscottle Well-Known Member

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    Aeons ago, there was a stone egg, upon a mountain top, ... Oh wait wrong story
    Aeons ago, when I was a teenager, I would resort to using a blowlamp for heavy stuff like this, since I only had a 30w Antex iron. Deep satisfaction. Would have thought it a better choice of tool for the roof of that ship too. (Though you'd want to be using a windshield or the wind would blow it out...)
     
  13. tvtech

    tvtech Well-Known Member Most Helpful Member

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    LOL :)

    I am learning :cool:

    Love you Guys,
    tvtech
     
  14. Willen

    Willen Well-Known Member

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    Hi, I saw a small soldering iron and its small power supply box. It has a pug to connect and disconnect the iron from power supply. The plug looks like 'Line in or out' plug. So I guessed the iron uses 12V or something low voltage DC. Actually why we need such low voltage power supply iron?
     
  15. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi there Willen,

    The ones i have seen all run at 24 volts. They usually use AC too not DC, which is a little surprising until you look at the control circuit. They can make the control circuit a little simpler by using AC controlling with a triac, and no rectifiers needed. The control is done by using multi cyclic control rather than instantaneous control, so they let several cycles pass all at once and then turn it off to control the temperature.
    The low voltage is a little safer to the user and to the circuit being worked on and makes the wiring to the iron a little simpler.
     
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  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The temperature of the tip of my Weller soldering iron is controlled mechanically, not electronically. The part of the tip that is inside the barrel of the soldering iron has a special piece of iron. The 24VAC switch inside the soldering iron has a rod with a magnet on it. When below the required temperature the magnet pulls on the iron piece and turns on the switch. When the iron piece reaches the desired temperature then it becomes non-magnetic and a spring releases the switch. It is called the "Curie" temperature.
    Tips are available with different temperature ratings. Mine is 700 degrees F which is 371 degrees C (ouch!).
    I hear the switch click on and off all day when it is turned on. In 51 years I never needed to replace the switch or spring. I replaced the tip only a few times and it has been turned on all day for most days.
     
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  17. throbscottle

    throbscottle Well-Known Member

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    Audioguru's much loved soldering iron gradually acquires mystical status.... Next instalment I'm sure we will learn of it's healing properties :O
    (Just teasing, AG, 'cuz I'm jealous :) )
     
  18. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Wow that's strange, as usually we try to go electrical whenever possible and loose the mechanical whenever possible because normally electrical is more reliable.

    BTW, you are saying that the switch is in the tip itself or in the cooler body?

    How many hours per day would you say you have used that iron, or at least kept it turned on?

    Sadly to say, even that soldering iron's birthday came after mine :)
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Healing? One time I cut my hand then I "accidently" cauterized it with my soldering iron. The bleeding stopped immediately.

    I have no idea how many hours my old soldering iron has worked. Sometimes I find it still turned on in the morning.
     
  20. throbscottle

    throbscottle Well-Known Member

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    There ya go! :D
     
  21. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Test table may be flawed with Average power vs peak power In PWM controlled heaters
     

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