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Help about fridge protector delay time

Discussion in 'General Electronics Discussion' started by Miguel Lopez, Feb 25, 2019.

  1. Miguel Lopez

    Miguel Lopez

    246
    55
    Jan 25, 2012
    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
     
  2. Kabelsalat

    Kabelsalat

    102
    19
    Jul 5, 2011
    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 ?
     
  3. Bluejets

    Bluejets

    3,432
    697
    Oct 5, 2014
    Front label says "microcomputer design" so more than likely there is a microcontroller with the "timing" is built in to the program.
     
  4. Bluejets

    Bluejets

    3,432
    697
    Oct 5, 2014
    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.
     
  5. Miguel Lopez

    Miguel Lopez

    246
    55
    Jan 25, 2012
    Thank you all for your answers

    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

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

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

    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.

    That's similar to the one I presented
     

    Attached Files:

  6. Alec_t

    Alec_t

    2,619
    693
    Jul 7, 2015
    Yes.
     
  7. Miguel Lopez

    Miguel Lopez

    246
    55
    Jan 25, 2012
    Is it possible to vary such time base by adding external components?
     
  8. Bluejets

    Bluejets

    3,432
    697
    Oct 5, 2014
    No.
     
  9. Miguel Lopez

    Miguel Lopez

    246
    55
    Jan 25, 2012
    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
     
  10. Bluejets

    Bluejets

    3,432
    697
    Oct 5, 2014
    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 ..........
     

    Attached Files:

  11. Miguel Lopez

    Miguel Lopez

    246
    55
    Jan 25, 2012
    Internal 4 MHz RC oscillator.......great....

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