Making a temperature controller for a soldering iron tip

Making a temperature controller for the soldering iron tip I bring to your attention the topic:“ Making a temperature regulator for the soldering iron tip ”.
I bought it in 2019. through the online store “ALI-EXPESS” 20 Watt small soldering iron and immediately convinced of its originality. At first, the tip of the soldering iron was surprised, which was an ordinary piece of iron nail 4mm in diameter, a short power cord with a “not our” plug, an elevated temperature of the soldering iron tip (does it even melt lead, did you regret it for tungsten?) Why the plastic handle got hot, you can't hold it.
I had to replace the tip (a piece of copper d = 4mm wire), insulate it with a Teflon strip and install an additional mount on the handle, and make a thyristor voltage (temperature) regulator for the soldering iron tip. The circuit has been known for a long time, it is available on the Internet, there is also a description of the work and oscillograms. It was assembled on a breadboard to fit the parts. on the Internet, in the same schemes, the denominations of the parts are different. In addition, the circuit is symmetrical, you can supply 220 V on the left, and connect the soldering iron on the right, on the contrary for me: 220 V is supplied on the right, and the soldering iron is connected on the left. If the R2 slider is moved to the left, the thyristor will not turn on, the soldering iron (~ 110 V) receives voltage through the diode D1, the “heating” mode. In the right position of the R2 engine, the soldering iron is supplied with full mains voltage (~ 220 V).
Here is the diagram:
Making a temperature regulator for the soldering iron tip About the details. I tried thyristors: KU101A, B, E, KU103B – all behave the same. Diode D1 KD105 or KD209 with any letter. Variable resistor R2, in the first copy – 150 KOhm, on the breadboard – 47 KOhm (which I found in the store), but better than 100 – 120 KOhm, with such the greatest smoothness of voltage regulation. Moreover, similar in appearance, they have different brands: SP3-9a, SP-04, SPO-05, etc., the distance between the terminals is different for everyone, which will be reflected in the printed circuit board drawing. Do not put less than 33 KOhm, it will heat up, and more than 150 KOhm – there will be a dead (unregulated) zone when you turn the R2 engine. The same large scatter in the circuits for the capacitor C1: 4.7 -47 MkF, (preferably 10 -20 MkF) and the resistor R1: 2 -30 KΩ (2.7 KΩ), the product of which T (tau, time,) is responsible for thyristor opening angle: T = RC. For clarity, you can add, which I did, chain D2 (KD102, 105, 209), resistor R3, LED HL1. The LED smoothly turns on or off, depending on the rotation of the knob of the resistor R3, and the entire chain is connected from the side of the soldering iron to points A, B, and, in essence, indicates the angle of the thyristor. The LED is imported, with a diameter of 3 mm, but an interesting story happened with the resistor R3. At 220 Volts, R3 is about 100 Kom, the current is 2.5 mA, I tried it – too bright, it went up to … 6.6 MΩ (2 pcs. 3.3 MΩ in series) – it is on! Apparently, HL1 lights up from emissions when VS1 is turned on, or because of steep fronts, because at a current of 0.00004 A, (40 microamperes), the LED cannot light up!
Making a temperature regulator for the soldering iron tip The plug box was taken from a faulty Chinese-made charger on the body of which the stamp “TOPSTAR” is extruded. A year later, I came across exactly the same Chinese box, but with the stamp “AMT Style”. I decided to make the same regulator in it, but for a 90W soldering iron. But the question is, will the diode and thyristor stand and not heat up? To check, I soldered the circuit on a breadboard and loaded it with two lamps connected in parallel, 220 V and 60 W each. I connected one lamp – nothing heats up, two lamps – barely perceptible heating of the thyristor at a power of 120 W and an approximate current of 0.5 A (0.25A per diode and thyristor). How many times I am convinced of the excellent characteristics of Soviet thyristors and diodes, which have a very low internal resistance in the open state and with a large margin of voltage and power!
A properly soldered circuit does not need adjustment, except for the selection of R3 (from 100 KΩ and above), according to the desired brightness of the LED. Since there is enough space in the box, I used MLT-0.5 resistors, R3 consists of two resistors connected in series.
 Making a temperature regulator for the soldering iron tip Making a temperature regulator for the soldering iron tip And now about making.
First, we drill a hole d = 6mm and install a variable resistor in the box opposite the power plug. Cut off a piece of fiberglass with dimensions of 52: 17mm and adjust (with a file) to fit into the case. We take a piece of graph paper (you can from a notebook in a box) and wrap the future board in it, copper to paper. Draw the paths with a pencil, taking into account the dimensions of the parts used. Let's put it on, for example, with a sharpened nail, an awl. We take out the board from the paper, drill, marked with a center punch, holes d = 0.6 – 1.0 mm. We clean the board with a fine-grained (zero) sandpaper, transfer the drawing from paper to the board, first with a pencil, and then with the help of a glass reeder (tube) – tsaponlak. We put, carefully, with the pattern down, in a solution of ferric chloride so that the board floats. After a time of 5-30 minutes, depending on the quality of the solution, if the board is thin, illuminating the board from above, you can see the etched pattern of the tracks. Tsaponlak is easily removed if acetone is dropped on a wet cloth (cotton wool). We clean it again with a “zero”, wipe (necessarily!) From dust and apply a solution of rosin in acetone (1: 3) to the tracks with a brush. alcohol, officially, for the solution, can not be bought anywhere. Maybe for the best, acetone dries quickly. The bottle with a brush is a former container of nail polish. The pattern on the board is simple and can be cut with a cutter. The board itself is fixed in the case by soldering to the terminals of the variable resistor.
Making the temperature regulator for the soldering iron tip  Manufacturing temperature regulator for the soldering iron tip Sincerely – A. Serov.
Serov Alexander Fomich, born in 1948, retired, living in Baranovichi, Brest region, Belarus , email mail: [email protected]
Making a temperature regulator for a soldering iron tip


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