Help about fridge protector delay time

[Miguel Lopez]

Hi all

Recently a friend of mine brought me a fridge protector with the purpode to extent the timing period. It's a Hunter EL-1595.
https://gmtuercas.com/products/fr-elc-el-1595
Fridge protectors are very common in Cuba due to anomalies in our electrical distribution system. I have even built some of them for me and my family, so people think I'm the guru of fridge protectors (nothing more distant from reality) and they bring this devices to me when they have problems. The fact is that I can not find the source of timing in this device so I can not change its delay time. It has two capacitors for PSU filtering and two small SMD capacitors for the same purpose in the output of the 7805 and between the terminals 1 ans 8 of the only IC.

The IC has the markings deleted so I can not know which IC it is. It's an 8 pins SMD device. I ask you for help in order to know how could be possible for this circuit to generate the delay time and to change this delay. I have paralleled the small SMD capacitors with no result. The delay time remains fixed at 90 seconds and I would like to extent it to 5 minutes (+/-)

Any idea most welcomed

Thanks in advance

 

[Kabelsalat]

Hi.

Can you provide images of both side of PCB card?

Are you sure the markings on the smd chip is completely worn out? Do you have a LED flashlight for hand and can try to point at the chip from different angles ?

 

[Bluejets]

Front label says "microcomputer design" so more than likely there is a microcontroller with the "timing" is built in to the program.

 

[Externet]

Hi !
Perhaps may give some clues:
----> https://www.google.com/search?clien...490.13j4......0....1..gws-wiz-img.5i1VxTvqnQ0

----> http://store.microcontrollerslab.co...-and-over-voltage-protection-system-for-home/
And seems to be microcontrolled if the chinese are to be believed :
----> https://www.aliexpress.com/item/hig...sign-for-household-10A-15A-30A/537215921.html

 

[Bluejets]

Just be careful with some of the links as I had 2 warnings come up with Avast.
There is a video on one link but if you can understand it, you are better than I am.
Sounds like the bloke did the video with his head in a bucket.

 

[Miguel Lopez]

Thank you all for your answers

Can you provide images of both side of PCB card?

I took this picture, but I didn't took a picture of the other side. Anyway, the other side contains only the filter capacitors for PSU and measurement, the relay, and the droppers R-C. I will take a picture today to show tomorrow. In the shown picture, there is a 0,1uF soldered by me while attempting to change the delay

Are you sure the markings on the smd chip is completely worn out?

I think I am, anyway..........

Do you have a LED flashlight for hand and can try to point at the chip from different angles ?

..........I'll try that today at home. Will tell you tomorrow

there is a microcontroller with the "timing" is built in to the program.

Have to say that I know nothing about microcontrollers (that's a pendant subjet), but I think that even a PC needs a time base to work. Is it possible to built a time base inside the microcontroller, without external components (capacitors or xtals)? If so, this should be the case, and there is nothing that I could do.

And seems to be microcontrolled if the chinese are to be believed :
----> https://www.aliexpress.com/item/hig...sign-for-household-10A-15A-30A/537215921.html

That's similar to the one I presented

 

[Alec_t]

Is it possible to built a time base inside the microcontroller, without external components (capacitors or xtals)?

Yes.

 

[Miguel Lopez]

Is it possible to vary such time base by adding external components?

 

[Bluejets]

Is it possible to vary such time base by adding external components?

No.

 

[Miguel Lopez]

OK, it seems that it is not possible to extent the delay time so I think this topic is finished

Now, as I said before I know nothing about microcontrollers, so in order to improve my knowledge I beg all of you to allow me a little off-topic.

How can a time base be generated inside a microcontroller without capacitors or xtals?
A short explanation, just to make myself an idea. I understand I will not learn about this right now. Thanks

 

[Bluejets]

How can a time base be generated inside a microcontroller without capacitors or xtals

Who says they don't have these.

A quick look at any uC will show many have internal components.
External devices are usually added for more accuracy.

A quick look at the bottom of the first page for the 12c series will show internal osc.
Pdf enclosed ..........

 

[Miguel Lopez]

Internal 4 MHz RC oscillator.......great....

As said before, a pendant subject for me. Thanks a lot. This is my learning for today.