Zerocross test issue

Discussion in 'The Projects Forum' started by Benengineer, May 6, 2016.

  1. Benengineer

    Thread Starter Member

    Feb 6, 2016
    133
    2
    One more question. Since our unit is EL817, why can't choose 50% for Ii/Io ratio rather than choosing 300% ratio?
    Thanks
     
  2. Benengineer

    Thread Starter Member

    Feb 6, 2016
    133
    2
    So in this case, Vce= 0.1V in the data sheet?
     
  3. Benengineer

    Thread Starter Member

    Feb 6, 2016
    133
    2
    Since I am a bignner, I don't really undertand the data sheet. There is lot of things to learn.
     
  4. crutschow

    Expert

    Mar 14, 2008
    23,093
    6,850
    The ratio variation is from 50% to 300% unit-to-unit.
    You don't get to pick the value, only that the device with the stated suffix will have a unit-to-unit variation as shown in the data sheet for that suffix.
    Yes, as show in Figure 5 of the data sheet.

    Data sheets can be intimidating and somewhat cryptic at times.
    You just have to take some time and try to understand what all the parameters mean, sort of like learning a new language.
     
  5. Benengineer

    Thread Starter Member

    Feb 6, 2016
    133
    2
    Yes, I agree with you and i have to spend time to learn those parameters mean. But it is more important to meet a good advisor even though i have passion on it. I try to use conversion functionality to invite you. But I don't know why it does work. Don't you allow people to invite you?
    My problem is that I am not good at applying what I learned from the school when a circuit is complicated. for example, I try to debugg the circuit in attachment.
    I can see that as below:

    R48 and C22 are voltage divider V1 = VLF1* (1/2pifC22)/(R48+1/2pifC22); C73|| R21 and C78||C79||R23 + C77 are second voltage divider. V2 = V1* C78||C79||R23 + C77/(C73|| R21 + C78||C79||R23 + C77). C74 blocks DC. At 3 terminal of the amp, voltage is V2/2pi*f, current I = Vcc/2-V2/2pi*f/R24. it is very small. At feedback loop, R53//C30. C28 and C82 + R22 are other voltage divider V3 = V2/2pi*f.*(R32+C82/R32+C82+C28). V3/R32 = (Vo-V3)/R53. I can caculate very voltage. But I need people explain what the circuit is doing. I also compare a good unit voltate to the bad unit voltage with data.
    Good unit Bad unit
    TP45 528mV P-P 80mV p-p
    TP46 2V 1.04V
    TP47 0.68V 1.04V
    TP48 1.04V 0.96V
    TP49 1.32V 1.32V
    TP50 1.32V 1.32V
    TP51 2.72V 1.36V

    Thanks
     
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