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  1. walid1

    Salt-taster

    Hi I feel I am alone with this question. But in any case, I built the circuit and worked excellently. The question remains puzzled me is the importance of R1 (=470 ohm) when i tried to remove it, the red led is illuminate It remains as to whether or not there is a salt solution can anyone...
  2. walid1

    Salt-taster

    Now I have a Specific question which is: comparing the folloing figure: with this figure (salt0001): Noting that the voltage at pin 1 (Vo) = (e2-e1)(R2/R1) I note that e1 = 1.8 V e2 must be Slightly lower than e1, say e2 = 1.7V so Vo = (1.7-1.8)(220K/10K) = - 2.2 V If the solution resistance...
  3. walid1

    A very Urgent Question

    I am sorry I forgot to thank elix for his interest and involvement Thank you very much
  4. walid1

    A very Urgent Question

    Hi dear guru you are absulutely true You are wonderful, you are the better man i have dealt with him in the electronics you our great teacher, thank you very much Yes, using two supply bypass capacitors at the 555 fixed the problem Whatever I said I will not be able to express my deep...
  5. walid1

    A very Urgent Question

    Hi guru Yes I forgot to attach the schematic of the "person detector" that drives the LED The schematic is attached below from: http://www.electronic-circuits-diagrams.com/alarmsimages/alarmsckt19.shtml As u see, it is a Tx and Rx I used one IR LED and not two I put the two units in front of...
  6. walid1

    A very Urgent Question

    Hi I built a circuit that when a person pass some red led illuminate This signal is connected to a pic to count. The problem is that when that person pass, the led is Intermittent lighting glows irregular and weaken and boosted in a very short time The pic see that several persons How can...
  7. walid1

    A sleep Timer

    At the outset extend deep thanks to Mr. AUDIOGURU for his effort and interest and wonderful answers. In truth, I thought the circuit was working in a different way, but now the picture clarified somewhat. Still I have some questions: (1)I am confident that your true 100%, but I can not...
  8. walid1

    MNA question about amplifier

    Hello, Have a look at the amplifier circuit shown I want to know your views about it..... if u find any mistake in it, do point it..... one stage to be mosfet was the requirement, so i have used the mosfet as voltage amplifier and then connected it to the power amplifier...... Thanx for...
  9. walid1

    transformers

    Hi I make a google search "transformrs core materials " i get many information, the followinf is an example: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650009347_1965009347.pdf hope it benefeted you
  10. walid1

    Calculating Total Reactance

    Hi at a certain freq Xl = Xc so the series Z = 0 and the parallel Z = infinity if you still confused, please choose some values to C and L and try calculate Z at different frequencies.
  11. walid1

    Salt-taster

    Hi I built this circuit on a test board http://www.redcircuits.com/Page68.htm the sensing leads are simply two thin copper wires i connect these two leads together, this equivalent to a very low resistive solution. when operate the circuit, the red led (D3) is on and the other green and yellow...
  12. walid1

    A sleep Timer

    Hi guru First, thank you very much A thyristor has 3 terminals; A1, A2 and G. Can you please mark these terminals on the schematic (Q1 & Q2). I think they are as shown in the following fig.thyq1q2-001 In the above Fig, and if my idea is true, this thyristor is triggered when a 0 volt signal...
  13. walid1

    A sleep Timer

    Hi Three days and there was no answer or response, this means that what I said is true and the original writer of the article was wrong. I have another question: We know that Pin 3 of 4060 turns from Low to the High after half an hour. This High signal is applied to the emitter of Q2 through...
  14. walid1

    A sleep Timer

    Hi The following circuit is function as a sleep timer: from: http://www.redcircuits.com/Page4.htm I edited it and put the parts values and some other information The writer wrote the following about it: {After turn-on by P1 pushbutton, the LED illuminates for around 25 minutes, but then it...
  15. walid1

    Transformerless power supply discussion!

    Hi I answer myself look at the followig figure: At the +ve half of the main AC voltage (311 V peak) the upper zener acts as a diode and the lower zD2 acts as a zener regulating the voltage to 16.7v At the -ve half of the main AC voltage (-311 V peak) the lower zener acts as a diode and the...
  16. walid1

    NAND gate

    thank you guru but i think if one o/p high =5v the other o/p low = 0 volt so it will sink all the current and the LED OFF what would u say
  17. walid1

    Transformerless power supply discussion!

    I asked why ZD1 and ZD2 in this schematic
  18. walid1

    NAND gate

    Hi look at the figure shown below: you noticed that the two nand gates have the same inputs, so they willl have the same outputs the led is always on till all the i/ps are High my question: if the two nand gates have not the same inputs, and the o/p of one of them is high and the other is low...
  19. walid1

    Transformerless power supply discussion!

    ok thanks guru in the following schematic: Why ZD1 and ZD2? thanks
  20. walid1

    Transformerless power supply discussion!

    hi guru to the following circuit, (1)if i changed it to be a half wave rectifier, is the current still 15 mA as with full wave (2) what the difference of putting a 300 ohm resistor in place of the red line or blue line in the followin circuit. thanks
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