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  1. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    Hi guru yes i see it. questions: 1- what is the minimum value of  R4 to make T1 not smoking? 2-If I remove this LED, put the correct value of R4 and we know that the relay resistance is 200 ohm,  what  the value of VC at T1? 3- I have many relays, there is no resistance value printed on its...
  2. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    Hi guru It is a good answer and excellent, but it opened the way to further questions. 1-I believe that these calculations were in the case of D5 still in the circuit. If we remove this D5 entirely from the circuit, Are these calculations remain as they are? 2-is there a darlengton pair...
  3. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    Hi I put the scheme to make the discussion easier. To guru why? To AN920 Guru said: what u say? thank you very much
  4. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    yes yes thank you very much, it is clear now. still the question #3 can u tell me something about it?
  5. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    Hi AN920 please can u explain it more using a numeric example. thanks
  6. walid1

    OVER-/UNDER-VOLTAGE PROTECTION CIRCUIT ANALYSIS

    Hi The circuit attached below is OVER-/UNDER-VOLTAGE PROTECTION. I have some questions: 1- R4 & R8 are 1K why not 10K? 2- Why D5? 3- the voltage divider consisting of the resistors R1, VR1 and R2, is to monitor the voltage, i can use the same voltage division with smaller or bigger values...
  7. walid1

    ringing detection circuit

    Hi guru It is a good point for me to put in my memory. But there remains a question: whether such a diode (4148) can bears this 127v ? Hi  mvs sarma This point is excellent and wonderful, thank you
  8. walid1

    ringing detection circuit

    Hi summersnow thank u very much for your reply can u please explain it more with numerical example.
  9. walid1

    ringing detection circuit

    Hi guru ok thank you i understand it. another question: why D3?
  10. walid1

    LM308 maximum ratings

    NOW I Understand thank you guru very much
  11. walid1

    ringing detection circuit

    Hi guru Now I'm  have a question: in your circuit shown below: why using two back to back 15v zeners. What they exactly do? thank you
  12. walid1

    LM308 maximum ratings

    hi guru In fact, I did not understand anything from what u said. I know that the differential voltage is the difference between the two voltages applied to the two i/ps; the inverting and non-inverting. can you explain it more? thanks
  13. walid1

    transistor as a switch

    Hi guru part of the 555 schematic is shown below. yes, It is ok, there is a darlington emitter follower, but why not two 0.6 or two 0.7 volt. why different VBE? thanks
  14. walid1

    LM308 maximum ratings

    Hi all my friends In the datasheets of  Lm308 attached below (at the end) I cut this part for discussion: and here are the notes: my questions: 1- What is the differential i/p current, and how to ensure that it will not exceed    10mA? 2- Please explain Note 1, I did not understand it...
  15. walid1

    transistor as a switch

    hi guru 5.6/6.8 = 82% is the output high of the 555 is always about 82% of Vcc? thanks
  16. walid1

    IC controlled emergency lamp with charger

    Hi guru unless R3 = R4 the charge time will not = the discharge time in the circuit R3=820 and R4=1000, why not equal? thank you
  17. walid1

    very simple PS

    thank you Ante
  18. walid1

    very simple PS

    Hi how did u know it is 200mA, can u please explain it for me thank you
  19. walid1

    IC controlled emergency lamp with charger

    Hi my best guru I can't discribe my feeling, you really the MAESTRO of this great site u make the information appeared in the photo below, you make it very clear. thank u guru, I wish you all the best in the world yours walid
  20. walid1

    transistor as a switch

    To guru thank u very very much you are good and expert man. this is a part of a circuit shown in the following link: http://www.electronics-lab.com/forum/index.php?topic=10229.0 it is an IC controlled emergency lamp with charger
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