Hello,

I built the attached schematic and I wanted to find if the TL431 oscillates, using an oscilloscope.
I tested by connecting the ground probe to the 220uF capacitor ground and the detachable hook to TL431 catode.
The measurements were made when the soldering iron was connected into the circuit.

1. Can you please explain if there are oscillations in the screenshots ?
2. It is normal to be multiple sine waves in the same screenshot, as it is in MAP002 and MAP003 ?

 

Hello,

I built the attached schematic and I wanted to find if the TL431 oscillates, using an oscilloscope.
I tested by connecting the ground probe to the 220uF capacitor ground and the detachable hook to TL431 catode.
The measurements were made when the soldering iron was connected into the circuit.

1. Can you please explain if there are oscillations in the screenshots ?
2. It is normal to be multiple sine waves in the same screenshot, as it is in MAP002 and MAP003 ?

I'll start with a disclaimer that I don't have hands-on experience with a TL341 or similar devices. However, since you have no other responses yet, I'll give you my best guesses.

1) There's a lot of variety in those screen shots. I'm not sure if that's oscillation, or just induced noise creeping in or slipping through.

2) Depending on your scope settings, and whether this was with single trigger or normal trigger mode, could be normal. See:
https://www.eevblog.com/forum/testgear/multiple-traces-after-stop-button-is-pressed/

 

Hello, I have a simple question about the attached schematic: does Rx = 100k (marked on the schematic) protect the soldering iron from overheating if one or both wires from the thermocouple is disconnected ?

 

Yes, it will make the input of IC2A go high. The comparator will then turn off the power to the element.
Keith

 

Hello, same question about the attached schematic. Does Rx1 (100k at the thermocpule amplifier block) protect the soldering iron from overheating if one or both thermocouple wires are disconnected ?
The project is from: http://electronics.vlzqz.com/home/lm324-analog-soldering-station

 

Also, I saw that using MOC3041 makes the LED flashing at a higher frequency in comparison to when using MOC3021.

 

Same answer:
Yes, it will make the input of IC2A go high. The comparator will then turn off the power to the element.
Keith

 

I designed an almost identical circuit that avoids the complexity of isolating the trigger circuit. I powered the soldering iron from the un-smoothed, rectified 24 volts ac. That way I could switch it with a power MOS FET. The diode shown in the diagram connected to R8 is a red LED.
I used an inexpensive 2.3 to 30 volt digital meter to indicate the temperature. It works very well.
View attachment 159079

why the diagram shows the Source connected to the ground while in component schematic the Source is connected to the iron?

 

why the diagram shows the Source connected to the ground while in component schematic the Source is connected to the iron?

You are correct. Thank you for pointing it out. The Source should be connected to ground. I don't know how I missed that one in the documentation. I guess I connected it correctly on the one I built because it still works great.

 

You are correct. Thank you for pointing it out. The Source should be connected to ground. I don't know how I missed that one in the documentation. I guess I connected it correctly on the one I built because it still works great.

 

Thanks for the reply. Can you also confirm that the mosfet used is irfz40?
Thanks for the reply. Can you also confirm that the mosfet used is irfz40?

 

Thanks for the reply. Can you also confirm that the mosfet used is irfz40?

Thanks for the reply. Can you also confirm that the mosfet used is irfz40?

Yes, it's an IRFZ40. If you are building one, I hope it works as well as the one I made.
Regards,
Keith.

 

Yes, it's an IRFZ40. If you are building one, I hope it works as well as the one I made.
Regards,
Keith.

View attachment 205069

It looks like a really good project. I'm already working on the circuit. Just two things:
-what type of transformer do you suggest me to use?
-what kind of iron handle can i use? (heating element A1321-A1322.....)
Regards.
Ed.

 

It looks like a really good project. I'm already working on the circuit. Just two things:
-what type of transformer do you suggest me to use?
-what kind of iron handle can i use? (heating element A1321-A1322.....)
Regards.
Ed.

I used an old Radioshack transformer with 12.6-0-12.6V 2A secondary. I ordered the parts for the Iron from Aliexpress.

Handle:
https://www.aliexpress.com/item/32835896063.html?spm=a2g0s.9042311.0.0.27424c4dkG15vZ

Tip bushing:
https://www.aliexpress.com/item/32724325226.html?spm=a2g0s.9042311.0.0.27424c4d10urTx

Element:
https://www.aliexpress.com/item/32691098329.html?spm=a2g0s.9042311.0.0.27424c4d1wtGnV

Connectors:
https://www.aliexpress.com/item/32866277697.html?spm=a2g0s.9042311.0.0.27424c4d10urTx

 

I used an old Radioshack transformer with 12.6-0-12.6V 2A secondary. I ordered the parts for the Iron from Aliexpress.

Handle:
https://www.aliexpress.com/item/32835896063.html?spm=a2g0s.9042311.0.0.27424c4dkG15vZ

Tip bushing:
https://www.aliexpress.com/item/32724325226.html?spm=a2g0s.9042311.0.0.27424c4d10urTx

Element:
https://www.aliexpress.com/item/32691098329.html?spm=a2g0s.9042311.0.0.27424c4d1wtGnV

Connectors:
https://www.aliexpress.com/item/32866277697.html?spm=a2g0s.9042311.0.0.27424c4d10urTx

OK.
Thanks.
Regards,
Ed.