ylectronick
Newbie level 1
HEATING ISSUE FIXED
Hello world!
I have used these 10 x 15mm converter modules from aliexpress for more than 3 years now, probably around one hundred of them. Just recently, on my last 20 or so circuits I stumbled on this fire hazard issue. I used all the advice I can gather from different forums and I want to share my full recipe in the order I tried them because I reached a really stable behavior witch doesn't consume much current and is also protected somewhat:
1 - first I tried pull-up resistors 10k (on some forums they say that unused ttl pins should be grounded, but I measured some uart pins and for me it makes more sense to pull them up) // this increased the stability a bit but it did not solve it completely.
2 - next, in addition, I limited the current that module eats by putting that 20 ohm resistor in series with VCC. Here the behavior was the same as at the previous step with the mention that when the chip would latch up it would get warm not freaking hot. So I left it like this, considering it a minor improvement.
3 - next I added 100 ohm resistor on the rs232 pins. Personally I did not notice a change, but there is at least another person on some forum saying that he could see improvements. I tend to believe this, (I'm sorry I cannot mention him. I'm bad with ID's after reading all the posts in a 3 google results page) it will serve as a current limiting protection...
4 - next, I added a 47uF electrolytic cap on the power pins in between the 20 ohm resistor and vcc. Again same story, somebody else stated that it fixed him. Of course not mine. I left it in circuit.
5 - next I added a 20 ohm resistor series on the ttl pins. No change, left it there. May serve as a protection, not to draw too much current from the micro-controller pin.
6 - I moved the power rail from 5V to 3.3, keeping all the parts mention above.
This totally solved the issue for me. At this point I had a procedure developed to make the thing latch. I was powering the converter first, and then connecting rs232 line then disconnecting it and also removing the micro-controller link.
Now I tried all the things I could and I cannot get it to heat up again.
Cheers, Nick
Hello world!
I have used these 10 x 15mm converter modules from aliexpress for more than 3 years now, probably around one hundred of them. Just recently, on my last 20 or so circuits I stumbled on this fire hazard issue. I used all the advice I can gather from different forums and I want to share my full recipe in the order I tried them because I reached a really stable behavior witch doesn't consume much current and is also protected somewhat:
1 - first I tried pull-up resistors 10k (on some forums they say that unused ttl pins should be grounded, but I measured some uart pins and for me it makes more sense to pull them up) // this increased the stability a bit but it did not solve it completely.
2 - next, in addition, I limited the current that module eats by putting that 20 ohm resistor in series with VCC. Here the behavior was the same as at the previous step with the mention that when the chip would latch up it would get warm not freaking hot. So I left it like this, considering it a minor improvement.
3 - next I added 100 ohm resistor on the rs232 pins. Personally I did not notice a change, but there is at least another person on some forum saying that he could see improvements. I tend to believe this, (I'm sorry I cannot mention him. I'm bad with ID's after reading all the posts in a 3 google results page) it will serve as a current limiting protection...
4 - next, I added a 47uF electrolytic cap on the power pins in between the 20 ohm resistor and vcc. Again same story, somebody else stated that it fixed him. Of course not mine. I left it in circuit.
5 - next I added a 20 ohm resistor series on the ttl pins. No change, left it there. May serve as a protection, not to draw too much current from the micro-controller pin.
6 - I moved the power rail from 5V to 3.3, keeping all the parts mention above.
This totally solved the issue for me. At this point I had a procedure developed to make the thing latch. I was powering the converter first, and then connecting rs232 line then disconnecting it and also removing the micro-controller link.
Now I tried all the things I could and I cannot get it to heat up again.
Cheers, Nick
