Soldering station (CA3130 and LM393)

[mike_mike]

I would like to know how can I implement hysteresis in this circuit (LM393) ?
I read on the internet a few pdfs and I found that there are a few methods for calculating the hysterezis, but I don't know which one to apply and how, because I have the signal from the sawtooth generator and the signal from the potentiometer and thermocouple amplifier.

[Kleinstein]

The resistor from pin 1 to 3 is already a frist step towards hysteresis. It would need an additional sereies resistor for the signal going to pin 3.

In the original plan the "triangle" signal is rather high impedance and thus not that well suited. One could use the spare half of the LM358 as a buffer or build directly a 2 OP version the triangle generator.

[mike_mike]

Instead of just asking, put some more effort into analyzing and understanding how and why the circuit works.
Once you've learned how these discrete parts work, it's easy enough to figure out the workings of such simple circuits.

@Doctorandus_P I tested today the attached schematic, using a 24Vdc/2.5A power supply and it seems to work. I would like to know if further modifications are needed ?

[mike_mike]

Please find attached a few screenshots with the pin 1 of LM393 (yellow trace) and pin 3 of LM393 (blue trace).
1. DS0102 = pin 1 (yellow) and pin 3 (blue)
2. DS0103 and DS0104 = Zoom in to DS0102
3. DS0106 and DS0107 = With 1M resistor between pin 1 and pin 3 of LM393

I find some oscillation between on and off at the latest 4 screenshots. Are they normally or not ?
Please have a look at the attached screenshots and tell me what you think ?

[mike_mike]

I was told to use 2 resistors as shown in the attached schematic.
Now, the screenshots from the oscilloscope look like: DS0113, DS0114 (yellow trace on pin 1 of LM393).

Please have a look at the schematic and at the screenshots and tell me what you think ?

[mike_mike]

I am using this soldering station for about 1 year. Yesterday I installed the pcb into a new case, and I saw on the oscilloscope screen the attached wave forms: yellow is pin 1 of LM393 and blue is pin 3 of LM393.
What are the spikes that are present on the blue trace ?

LE: The spikes happen even if I change the soldering iron with a new one. Also, I tested with the DC version of the soldering station and the spikes also appeared. Probably the spikes are because of the soldering iron heater which goes on-off

[mariush]

Mike, as an alternative,  you can get the Hakko 936 schematic online : https://www.histo.cat/files/files/200915145115281.pdf

You can replace the uPC1701c (zero crossing detection switch) / triac driver chip with UAA2016 which is still made, or you can get the uPC1701c from eBay.

You can also get ready made hand pieces from ebay and you can get ready made pcbs from ebay
For example : https://www.ebay.com/itm/295538863410  -3$ for board and components all but the DIN socket for the hand piece.
You can get hand pieces for 3-4$ example :  https://www.ebay.com/itm/153679091608

and 24v transformers you can find easily.

edit: sorry, didn't realize you got it working, only read a few of the first posts in the thread.

[mike_mike]

edit: sorry, didn't realize you got it working, only read a few of the first posts in the thread.

Yes, I made it working, and I used it for about 1 year.

My concerns were about the schematic because I didn't know if the schematic is good enough for a simple soldering iron (50W/24V/K- type thermocouple sensor) or if the schematic has wrong components ?
I added the hysterezis to U1A by adding the R24 (1M), R25 (10k), and C33 (100nF) to the circuit. The result was that the oscillation on the pin 1 of LM393 disappeared when I verified with the oscilloscope.
Also by changing the optotriac and triac with a Mos-fet and a mos-fet driver circuit I made the circuit working with 24V/3A SMPS.
I made the above modifications from the internet, they are not original.