Someone has remaked "Your "precise" temperature control is far from anything a decent solder station would do. You basically have a comparator that compares the set point and the feedback it gets from the thermistor. That thing overshoots, I guarantee it. A decent solder station needs a carefully tweaked PID control loop, whether it is analog or digital."
This is nonsense. Can you "guarentee it"?
Show me any video or any data to back up your claim for absolute need for a "carefully tweeked PID control loop,,or that other "Professional" soldering stations maybe hundreds of times more expensive are not also showing this behavior?
Having a "carefully tweaked PID control loop' implies a critical need that a competent soldering station has been equipped with a microcontroller and carefully tweaked software. I haven't yet to see even the uncommon use of any MCU in any soldering station schematic I've ever seen.
There is only reason for MCU's not being used, they are not necessary to achieve good temperature control.
First of all it is not necessary to control the temperature of any soldering iron within few degrees, soldering is a much an art as a skill and learning how to use the tools you have makes all the difference in using any soldering tool.
Even with the crudest of soldering tools, learning that soldering technique is a "touch and go" situation that can be learned as a skill, and having this skill can allow even a cigarette lighter heating a ball-point pen clip to be used to successfully solder/unsolder tiny SMD components. It does take a little practice.
Having any feedback loop, such as the very simple comparator circuit I've shown is in comparison, is a thousand time more able to stablize temperature and can rival the soldering ease of the most expensive stations.
The temperature of the tip of a soldering stations varies, it varies, with many factors, most notably, the thermal mass it is applied to, the power available to heat the heating element and the distance/thermal resistance from the heating element from the sensor and the tip and the thermal conductivity of the object being soldered and the surface it is soldered to, the time that tip is applied to the object to be soldered..etc. It is not constant.
I can only hope that English isn't your native language because your writing is damned near impossible to understand.
Anyway, I
think you're saying that you've never seen a soldering station that needed an MCU in its controller for anything other than display. This is utter nonsense. What others have explained to you about overshoot is not only true, it's also simple plain common sense. Ever notice how when people are filling a bottle with water (at the faucet), they'll slow down the flow at the end so it doesn't spray everywhere? Same principle.
Whenever you have momentum in a system (like thermal mass to overcome) and use only simple single-threshold, on-off control, you end up with oscillations. You see this with radiator central heating using "dumb" bimetallic strip thermostats, too: it takes a while to reach the setpoint, and when it does and the thermostat turns off, the excess residual heat in the system continues to heat the building well beyond the setpoint.
FWIW, my Ersa i-CON nano has three "power" settings (though I think "aggressiveness" would actually be a better word): high heats super fast but can have significant overshoot (I've seen 30C overshoot, enough to damage some components), low has zero overshoot (but takes much longer to warm up since it heats very gently at the end), and medium which is a good balance for everyday use (allows a few degrees of overshoot). The control system has, I believe, around 10 actual power levels, though the onscreen bargraph shows only 5 levels -- initial heatup happens at full power, and then as it approaches the setpoint, the power level is dropped down, and ultimately turned off at the setpoint. (If it couldn't regulate power levels like this, temperature stability would be much worse, with more overshoot, and with larger fluctuations overall.)
I think the point you're trying to make, Paul Price, is that not everyone needs a top-grade professional station. Nobody here actually disagrees with
that. What we disagree with is your casual statement that some $5* piece of junk (which may be good enough for many jobs) is just as good as professional equipment. It's not and never will be. Learn about false economies: saving up and spending $100 on a real station will not only last longer, but it'll also be a pleasure to use. Can you make a solder joint with a hot nail? Sure. Is it enjoyable to work that way? Absolutely not. Why waste time and enjoyment over such a trivial amount of money?
*Ignoring that it can't be done for $5. If you've spent $2.70 on that junky handle, you're still gonna need far more than $2.30 in parts to build the rest. It's rarely actually cheaper to build our own electronics -- Chinese factories are just too damned efficient. We do it for fun and learning, not to save money.
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